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Question 1 of 125

1. In a young man during exercise, the minute oxygen uptake and carbon dioxide emission equalled to 1000 ml. What substrates are oxidized in the cells of his body?

Explanation

Minute O2 uptake – 1000ml

    Minute CO2 emission – 1000ml

    Respiratory Quotient (RQ) = vCO2 /vO2 = 1000/1000(ml) = 1

   Carbohydrate = 1; Fat = 0.7; Protein = 0.8

2.

A sportsman spontaneously held breath for 40 seconds, which resulted in an increase in heart rate and systemic arterial pressure. Changes of these indicators are due to activation of the following regulatory mechanisms:

Explanation

Reflex activity is the response to a peripheral nervous stimulation that occurs without our consciousness. It can be:

* Inborn or unconditioned: present from birth, does not require previous learning or training.

* Acquired or conditioned: developed after conditioning or training. Acquired after birth.

It is unconditioned because the sportman did not learn it; it is natural. The symptoms like increase in heart rate (HR) & systemic arterial pressure (AP) are sympathetic. Therefore, UNCONDITIONED SYMPATHETIC REFLEX

3.

An animal experiment is aimed at studying the cardiac cycle. All the heart valves are closed. What phase of the cycle is characterized by this status?

Explanation

krushkrok No11 (2014)

Isometric or isovolumetric contraction period in cardiac cycle is the first phase of ventricular systole. There is increase in tension, without any change in length of muscle fibers. The volume does not change because all valves are closed.

Asynchronous contraction: myocardium is involved partly and the intraventricular pressure does not increase. Protodiastole is the first stage of ventricular diastole. Rapid filling – AV valves open, to admit blood into the ventricle. Reduced or slow filling – after the sudden rush of blood, the ventricular filling becomes slow.

4. Feces of a patient contain high amount of undissociated fats and have grayish-white color. Specify the cause of this phenomenon:

Explanation

image

Obturation (obstruction, to close) of bile duct – it can be:

* Intrahepatic – blockage of intrahepatic bile ducts

* Extrahepatic – blockage of common bile duct (ductus choledochus).

Findings:

* malabsorption: bile salts do not enter the Small Intestine; no emulsification of fat.

*light coloured stool: due to lack of urobilin (which leads to lack of stercobilin).

*Jaundice (posthepatic, mechanic, obstructive): increased conjugated Bilirubin.

* Steatorrhea

The findings are specific for obstruction of bile duct and bile acid deficiency.

5. A patient has increased thickness of alveolar-capillary membrane caused by a pathologic process. The direct consequence will be reduction of the following value:

Explanation

Alveolar capillary membrane (respiratory membrane): formed by epithelium of respiratory unit and endothelium of pulmonary capillary. Exchange of gases between blood & alveoli takes place through respiratory membrane & this exchange occurs through bulk flow diffusion.
6.

The processes of heat transfer in a naked person at room temperature have been studied. It was revealed that under these conditions the greatest amount of heat is transferred by:

Explanation

Heat Radiation is a way the surface of the human body emits heat to the environment in the form of infrared rays. The amount of heat the body radiates to the environment is proportional to the surface of radiation area and to the difference between the mean values of skin and environment temperature. The surface radiation area is the total surface area of body parts that contact the air. Elimination of heat by radiation increases with a decrease in ambient temperature and decreases with its increase. It is possible to reduce elimination of heat by radiation via reduction of the surface of radiation area (“winding oneself into a ball”). Heat radiation does not require a medium for transfer of heat. (Key words: naked or lightly clothed).

Convection is a way the body eliminates heat by means of transferring heat via moving particles of air or water. To dissipate heat by means of convection, body surface shall be airflowed at a temperature that is lower than the temperature of the skin. At that, air layer contacting with the skin warms up, decreases its density, rises and is replaced by cooler, denser air. By increasing the speed of the air flow (wind, ventilation) heat emission increases significantly as well (forced convection). Convection requires convection current; current of gases or liquids (Key words: air over exposed area of skin).

Evaporation is a way the body dissipates heat to the environment by its evaporation via sweat or evaporation of moisture from the skin and respiratory tract mucous membranes of (“wet” heat loss). Evaporation closely related to relative humidity.

Conduction is a way the body eliminates heat by means of direct contact with another object. Heat is transferred down the temperature gradient (i.e. from the object of higher temperature to the object of lower temperature). Conduction requires contact with another object (Key words:  in water).

7.

A patient has a traumatic injury of sternocleidomastoid muscle. This has resulted in a decrease in the following value:

Explanation

All muscles that elevate the rib cage are muscles of inspiration and those that depress the rib cage are muscles of expiration.

Muscles of inspiration:

·        Sternocleidomastoid: lift upward on the sternum.

·        Anterior serrati: lift many of the ribs.

·        Scalene: lift the first two ribs.

Muscles of expiration: Abdominal recti – pull down the lower ribs and other abdominal muscles also compress the abdominal contents upwards against the diaphragm and internal intercostals.

Normal respiration is accomplished by the movement of the diaphragm only.

8. During  an  animal  experiment, surgical damage of certain brain structures has caused deep prolonged sleep. What structure is most likely to cause such condition, if damaged?

Explanation

Reticular formation is a diffused mass of neurons and nerve fibers which form an ill-defined meshwork of reticulum in central portion of the brainstem. Functions: Ascending reticular activating system (ARAS) and descending reticular system. The ARAS is concerned with arousal, alertness, attention and wakefulness, emotional reactions, learning processes and conditioned reflexes. Hence, tumor or lesion in ARAS leads to prolonged sleeping or coma.

9.

When measuring total muscle action potential it was revealed that it was subject to the power-law relationship. The reason for this is that individual muscle fibers differ in:

Explanation

The larger the stimulus, the greater the depolarization or attempt to reach depolarization or threshold potential. The threshold value controls whether or not the incoming stimuli are sufficient enough to generate an action potential. The threshold potential is the critical level to which the membrane potential must be depolarized in order to initiate an action potential. Individual muscle fibers and tissues generally require different depolarization threshold potential for action potential to occur.

10.

A patient has insufficient blood supply to the kidneys, which has caused the development of pressor effect due to the constriction of arterial resistance vessels. This is the result of the vessels being greatly affected by the following substance:

Explanation

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↓blood supply → activates renin. Renin catalyzes the conversion of angiotensinogen to angiotensin I. Angiotensin converting enzyme (ACE) converts angiotensin I → angiotensin II. Angiotensin II causes:

- vasoconstriction → ↑BP

- vasopressin (ADH) → ↑H2O reabsorption → ↑plasma volume

- aldosterone → ↑Na+ and H2O reabsorption → ↑plasma volume → ↑BP

11.

Experimental stimulation of the sympathetic nerve branches that innervate the heart caused an increase in force of heart contractions because the membrane of typical cardiomyocytes permitted an increase in:

Explanation

IMG_9907IMG_9903

When a muscle is excited (stimulated) by the impulses passing through neuromuscular junction, action potential is generated which spreads over sarcolemma (plasma membrane of muscles). When the action potential reaches the cisternae of ‘L’ tubules, Ca2+ stored in the cisternae are released into the sarcoplasm (cytoplasm of muscles). The Ca2+ moves towards the actin filaments to produce the contraction. Therefore, it is Ca2+ entry into the sarcoplasm.

12.

In a cat with decerebrate rigidity the muscle tone is to be decreased. This can be achieved by:

Explanation

Decerebrate rigidity indicates brain stem damage, specifically damage below the level of the red nucleus. Vestibular nerve has 4 nuclei – superior(Bechterew’s), inferior(Roller), lateral(Deiter’s) and medial(Schwalbe’s). In the lateral vestibular nucleus, some fibers from this nucleus pass into the cerebellum, which is important in regulating muscle tone. It has been shown experimentally that destruction of this nucleus leads to loss of tone almost completely.

13. A patient complains of pain in the heart area during acute attack of gastric ulcer. What vegetative reflex can cause this painful feeling?

Explanation

*Viscerovisceral reflex: functional or organic disease of a viscera (organ) causes pain, irritation to another organ e.g gastric ulcer (stomach) – heart

*Viscerodermal reflex: organ-skin

*Visceromotor reflex: organ-muscle

*Dermatovisceral reflex: skin-organ

*Motor-visceral reflex: muscle-organ

This is because the skin and related organs or muscle have the same segmental innervations usually by dorsal roots, spinal nerves and nuclei (referred pain resulting from reflex phenomena).

14.

A female patient, having visited the factory premises with lots of dust in the air for the first time, has got cough and burning pain in the throat. What respiratory receptors, when irritated, cause this kind of reaction?

Explanation

Irritant receptors are located in the bronchi and bronchioles of lungs and are stimulated by irritant chemical agents such as ammonia, sulfur dioxide and some other small particles like dust, smoke etc. These receptors send afferent impulses to respiratory centers via vagal nerve fibers. Stimulation of irritant receptors produces reflex hyperventilation along with bronchospasm. J receptors are stimulated during pulmonary congestion, pulmonary edema, over-inflation of lungs. Stretch receptors are the receptors which give response to stretch of the tissues – Hering-Breuer reflex is initiated by the stimulation of stretch receptors of air passage. Proprioceptors of respiratory muscles are the receptors which give response to change in the position of body. Thermoreceptors are cutaneous receptors, which give response to change in the environmental temperature.

15.

Since a patient has had myocardial infarction, his atria and ventricles contract independently from each other with a frequency of 60-70 and 35-40 per minute. Specify the type of heart block in this case:

Explanation

Complete atrioventricular block (third degree heart block; complete heart block) is the condition in which the impulses produced by sinoatrial node (SA node) cannot reach the ventricles. Because of this, the ventricles beat in their own rhythm, independent of atrial beat. Partial or 2nd degree heart block: transmission of impulses produced from SA node fail to reach the ventricles. It iis slowed down and not blocked completely. Sinoatrial block is failure of impulse transmission from SA node to atrioventricular (AV) node. Intra-atrial block: transmission of impulse through atrial myocardium is impaired. Intraventricular block: conduction of impulse through His bundle and its branches is impaired.

16.

In an experiment a dog had been conditioned to salivate at the sight of food and a flash of light. After conditioning the reflex, the light was then paired with the bell. The dog didn’t start to salivate. What type of inhibition was observed?

Explanation

The dog is conditioned to salivate at the sight of food and flash of light – that is a conditioned reflex that requires learning, memory and recall of previous experience. The established conditioned reflexes can be inhibited: externally and internally. External inhibition: disturbing factors like a stranger, sudden noise (the bell) or a strong smell can abolish the conditioned reflex and inhibit salivary secretion. This extra stimulus evokes the animal’s curiosity  and distracts the attention. Internal inhibition can be:

*Extinction of conditioned reflex: failure to reinforce the conditioned reflex by unconditioned stimulus.

*Differential: alteration of conditioned stimulus.

17.

In course of an experiment there has been an increase in the nerve conduction velocity. This may be caused by an increase in the concentration of the following ions that are present in the solution around the cell:

Explanation

Nerve signals are transmitted by action potential (AP), which are rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane. During the depolarization stage of an AP, the membrane suddenly becomes permeable to sodium ion (Na+), allowing tremendous number of positively charged Na+ to diffuse to the interior of the axon. A major function of voltage-gated calcium ion (Ca2+) channels is to contribute to the  depolarizing phase on the action potential in some cells. Although the gating of calcium channel is slow (slow channels), in contrast to the fast sodium channels. Therefore, sodium channels play a key role in initiation and conduction of action potentials.

18.

A patient has severe blood loss caused by an injury. What kind of dehydration will be observed in this particular case?

Explanation

Dehydration (hypohydration, hypohydria, exicosis): in dehydration, the extracellular fluid (ECF) and sodium ions are lost.

*Isoosmolar dehydration: based on proportional volume decrease of fluids and electrolytes e.g. acute renal failure (stage of polyuria), blood loss, burns etc.

*Hypoosmolar dehydration (salt deficit) develops due to diarrhea, vomiting, sweating, adrenal insufficiency etc.

*Hyperosmolar dehydration (water deficit) develops due to the loss of the fluid which lacks electrolytes e.g. in diabetes insipidus, hyperventilation

19.

A fixed-run taxi passenger has a sudden and expressed attack of tachycardia. A doctor travelling by the same taxi has managed to slow down his heart rate by pressing upon the eyeballs and thus causing the following reflex:

Explanation

Aschner’s reflex (press on eyeball) → ↓heart rate. This is mediated by nerve connections between the ophthalmic branch of trigeminal cranial nerve via the ciliary ganglion and the vagus nerve of parasympathetic nervous system.

Goltz reflex (press or blow to the epigastric region) → ↓heart rate.

20. A 36-year-old female patient has a history of B2-hypovitaminosis. The most likely cause of specific symptoms (epithelial, mucosal, cutaneous, corneal lesions) is the deficiency of:  

Explanation

Vitamin B2 (riboflavin): component of flavins FAD and FMN – which are the coenzyme forms. Deficiency causes cheilosis (inflammation of lips, scaling and fissures at the corners of the mouth), corneal vascularization.

21.

A blood drop has been put into a test tube with 0,3% solution of NaCl. What will happen to erythrocytes?

Explanation

image

The intracellular fluid of erythrocytes is a solution of salts, glucose, protein and hemoglobin. A 0.9% NaCl solution is said to be isotonic: when blood cells reside in such a medium, the intracellular fluid (ICF) and extracellular (ECF) are in osmotic equilibrium across the cell membrane and there is no net influx or efflux of water.

On the other hand, in a hypnotic environment (e.g. 0.3% NaCl or distilled water), an influx of water occurs; the cells swell, the integrity of their membranes is disrupted, allowing the escape of their hemoglobin (hemolysis) which dissolves in the external medium.

When subjected to hypertonic media (e.g 1.3% NaCl) the cells lose their normal biconcave shape, undergoing collapse (shrinkage leading to crenation) due to the rapid osmotic efflux of water.

22. In a dysentery patient undergoing treatment in the contagious isolation ward, a significant increase in packed cell volume has been observed (60%). What other value will be affected by this change?

Explanation

Packed cell volume (PCV) or hematocrit is the volume in percent of red blood cells (RBCs) in blood; 45% for men; 40% for women. So a PCV of 60% indicates a significant increase in RBCs in the blood which will directly increase the thickness of blood and cause vessel congestion as a result of increase in blood viscosity. Increased RBCs directly increase blood viscosity. Volume of blood will increase but volume is more closely related to the fluid component of blood.

23. A patient has the oxyhemoglobin dissociation curve shifted to the left. What blood changes induce this condition?

Explanation

When the curve shifts to the right, there is decrease affinity of hemoglobin for O2 (this facilitates unloading of O2 to tissues). An increase in all listed factors (including H+) causes a shift of the curve to the right. A decrease in the factors (including H+) causes a shift of the curve to the left. Fetal hemoglobin has higher affinity for O2 than adult hemoglobin, so its dissociation curve is shifted to the left.

Right shift (↑): acidosis(↑H+); CO2; exercise; 2,3-BPG; Altitude; Temperature. Hence left shift will be (↓): alkalosis(↓H+); hypocapnia(↓CO2); temperature decrease.

24.

It has been experimentally proven  that the  excitation   of  the  motor   neurons of flexor muscles is accompanied by the inhibition  of the  motor  neurons of extensor muscles. What  type of inhibition  underlies this phenomenon?

Explanation

krushkrok No8 (2013)

Reciprocal inhibition is the inhibition of antagonistic muscles when a group of muscles are activated, an important feature of both flexor and extensor reflexes, as a result of reciprocal innervation. Usually, excitation of  one group of  muscles is associated with the inhibition of another i.e. antagonistic group of muscles on the same side. E.g when a flexor reflex is elicited, the flexor muscles are excited (contracted) and the extensor muscles are inhibited (relaxed) in that side.

25. A  man  sitting  with  his  eyes  closed, undergoes electroencephalography. What rhythm  will be  recorded on  the  EEG if there  is an audible  signal?

Explanation

26.

Thermometry   revealed     that    the temperature of the  exposed  skin is by 1-1,5oC   lower  than  the  temperature of  the adjacent areas covered with clothing from natural fabrics. The reason  for this is that the clothes reduce  the heat loss through:

 

Explanation

The areas of the skin covered with clothes has a higher temperature because the convection current does not have direct access to the skin in that area as compared to the exposed area of the skin.

Convection is a way the body eliminates heat by means of transferring heat via moving particles of air or water. To dissipate heat by means of convection, body surface shall be airflowed at a temperature that is lower than the temperature of the skin. At that, air layer contacting with the skin warms up, decreases its density, rises and is replaced by cooler, denser air. By increasing the speed of the air flow (wind, ventilation) heat emission increases significantly as well (forced convection). Convection requires convection current; current of gases or liquids (Key words: air over exposed area of skin).

Heat Radiation is a way the surface of the human body emits heat to the environment in the form of infrared rays. The amount of heat the body radiates to the environment is proportional to the surface of radiation area and to the difference between the mean values of skin and environment temperature. The surface radiation area is the total surface area of body parts that contact the air. Elimination of heat by radiation increases with a decrease in ambient temperature and decreases with its increase. It is possible to reduce elimination of heat by radiation via reduction of the surface of radiation area (“winding oneself into a ball”). Heat radiation does not require a medium for transfer of heat. (Key words: naked or lightly clothed). 

Evaporation is a way the body dissipates heat to the environment by its evaporation via sweat or evaporation of moisture from the skin and respiratory tract mucous membranes of (“wet” heat loss). Evaporation closely related to relative humidity.

Conduction is a way the body eliminates heat by means of direct contact with another object. Heat is transferred down the temperature gradient (i.e. from the object of higher temperature to the object of lower temperature). Conduction requires contact with another object (Key words:  in water).

27. The temperature in a production room is  36oC .  Relative  air  humidity   is  80%. Under these  conditions the  human  body transfers heat mainly through:

Explanation

Evaporation is a way the body dissipates heat to the environment by its evaporation via sweat or evaporation of moisture from the skin and respiratory tract mucous membranes of (“wet” heat loss). Evaporation closely related to relative humidity.

Heat Radiation is a way the surface of the human body emits heat to the environment in the form of infrared rays. The amount of heat the body radiates to the environment is proportional to the surface of radiation area and to the difference between the mean values of skin and environment temperature. The surface radiation area is the total surface area of body parts that contact the air. Elimination of heat by radiation increases with a decrease in ambient temperature and decreases with its increase. It is possible to reduce elimination of heat by radiation via reduction of the surface of radiation area (“winding oneself into a ball”). Heat radiation does not require a medium for transfer of heat. (Key words: naked or lightly clothed).

Convection is a way the body eliminates heat by means of transferring heat via moving particles of air or water. To dissipate heat by means of convection, body surface shall be airflowed at a temperature that is lower than the temperature of the skin. At that, air layer contacting with the skin warms up, decreases its density, rises and is replaced by cooler, denser air. By increasing the speed of the air flow (wind, ventilation) heat emission increases significantly as well (forced convection). Convection requires convection current; current of gases or liquids (Key words: air over exposed area of skin).

Conduction is a way the body eliminates heat by means of direct contact with another object. Heat is transferred down the temperature gradient (i.e. from the object of higher temperature to the object of lower temperature). Conduction requires contact with another object (Key words:  in water).

28. During  the  fight, a man  had  a cardiac arrest  due  to  the  strong  blow  to  the upper  region  of  the  anterior abdominal wall. Which of the following mechanisms has led to the cardiac arrest?

Explanation

Goltz’ reflex: by pressing/strong blow to the epigastric region produces parasympathetic responses. Aschner’s reflex: press on the eyeball produces similar parasympathetic effects. They are parasympathetic reflexes and because no prior learning is involved – it is an unconditioned reflex.

29.

An attack of tachycardia that occurred in a patient was stopped by pressing on his eyeballs.  Which  of the  following  reflexes underlies this phenomenon?

Explanation

Aschner’s reflex (press on eyeball) → ↓heart rate. This is mediated by nerve connections between the ophthalmic branch of trigeminal cranial nerve via the ciliary ganglion and the vagus nerve of parasympathetic nervous system.

Aschner’s reflex: press on the eyeball produces similar parasympathetic effects. Goltz’ reflex: by pressing/strong blow to the epigastric region produces parasympathetic responses. They are parasympathetic reflexes and because no prior learning is involved – it is an unconditioned reflex.

30. Workers of a conveyor  workshop received recommendations for the effective organization of working  time  and  higher  working  efficiency.  What  peculiarity of work in this workshop  causes the greatest stress for the workers?

Explanation

Stress is not a disease or injury but it can lead to mental and physical ill health. We are concerned about the mental health in this question. Now the workers have been recognized and appreciated for a job well done which is a fundamental human need. The stress related hazard in this work now will be the job content (monotony), in which they are made to do the same thing always and repeatedly. This leads to unhappiness and boredom.

31.

For   the   study   of  serum   proteins various physical and physicochemical methods  can be used. In particular, serum albumins  and  globulins  can be separated by this method:

Explanation

Electrophoresis uses the principle of electric charge size and shape to separate substances. Proteins carry a positive or a negative electrical charge and they move in fluid when placed in an electrical field. The two major types of protein present in the serum are albumin and globulin proteins. Albumin is the major protein component of serum and represents the largest peak that lies closest to the positive electrode. Globulins comprise a much smaller fraction of the total serum protein but represent the primary focus of interpretation of serum protein electrophoresis. Five (5) globulin categories are expressed – α1, α2, (alpha 1 & 2), β1, β2 (beta 1 & 2) and ɣ (gamma). ɣ is the closest to the positive electrode.

32. An  animal  has  an  increased   tonus of extensor muscles.  This is the  result  of enhanced information transmission to the motoneurons of the  spinal  cord  through the following descending pathways:

Explanation

Vestibular nuclei receive impulses concerned with muscle tone and posture from vestibular apparatus and cerebellum. Vestibular nuclei in turn convey the impulses to different parts of the body through the anterior and lateral vestibulospinal tracts. Vestibulospinal tracts are concerned with adjustment of position of head and body during angular and linear acceleration; maintenance of muscle tone and posture; position of head and body during acceleration. Therefore, increase transmission of impulse through this tract leads to increase tone. Extensor muscles are also for balance (connected to vestibular apparatus). The inputs from the otolith organs project mainly to the lateral vestibular nucleus, which in turn sends axons in the lateral vestibulospinal tract to the spinal cord. The input from this tract exerts a powerful excitatory influence on the extensor (antigravity) muscles. When hair cells in the otolith organ are activated, signals reach the medial part of the ventral (anterior, motor) horn. By activating the ipsilateral (same side) pool of motor neurons innervating extensor muscles in the trunk and limbs, this pathway mediates balance and the maintenance of upright posture.

33.

A  19-year-old   male  was  found   to have  an  elevated level  of  potassium   in the  secondary urine.  These  changes  might have  been  caused  by the  increase  in the following hormone level:

Explanation

Aldosterone produced in adrenal cortex (zona glomerulosa): causes increased sodium (Na+) reabsorption; increased potassium and hydrogen ions (↑K+, H+) excretion. They increase sodium (↑Na+) channel and Na+ /K+-pump insertion in principal cells of collecting duct; enhances K+ and H+ excretion by way of principal cell K+ channels and α-intercalated cell H+ ATPases of collecting duct. Therefore, increase in aldosterone → ↑ K+ in urine (excretion) and ↓ Na+ in urine (↑ reabsorption); And decreased aldosterone → ↓ K+ excretion (↓K+ in urine) and ↓ Na+  reabsorption (i.e. ↑Na+ in urine); same effects on sweats glands too.
34. To assess the effectiveness  of breathing in patients, the indicator of functional residual  capacity  is used.  It  includes  the following volumes:

Explanation

image

Functional residual capacity (FRC) is the volume of air remaining in the lungs after normal expiration (after normal tidal expiration). It includes expiratory reserve volume (ERV) and residual volume (RV).  FRC = ERV + RV

35.

It is required to evaluate the level of tissue  excitability.  For  this  purpose one should determine:

 

Explanation

The larger the stimulus, the greater the depolarization or attempt to reach depolarization or threshold potential. The threshold value controls whether or not the incoming stimuli are sufficient enough to generate an action potential. The threshold potential is the critical level to which the membrane potential must be depolarized in order to initiate an action potential. Individual muscle fibers and tissues generally require different depolarization threshold potential for action potential to occur.

36.

During  ventricular systole, the cardiac muscle does not respond to additional stimulation because  it is in the phase of:

Explanation

krushkrok No145 (2013)

Absolute refractory period is the period during which the muscle does not show any response at all, whatever may be the strength of the stimulus. It is because the depolarization occurs during this period. So, a second depolarization is not possible in cardiac muscle, absolute refractory period extends throughout systole (contraction) period – 0.27sec. And, relative refractory period extends during first half of diastole (relaxation) period – about 0.26sec. Relative refractory period is the period during which the muscle shows some response if the strength of stimulus is increased to maximum.

37.

A male working  as a blacksmith  has been  tested  for auditory acuity. The  tests revealed 50% hearing loss in the low- frequency range  and a near-normal auditory  acuity  in the  high-frequency range. This condition has been caused by the damage  to the following structures of the auditory system:

Explanation

FullSizeRender (26)FullSizeRender (25)

Two membranes divide the spiral canal of cochlea into 3 compartments – vestibular and basilar membrane. Along the basilar membrane are 20,000-30,000 tiny fibers called basilar fibers. Each fiber has different size and shape. Fibers near the oval window (base) are short and stiff (narrowest), while approaching towards helicotrema (apex), the basilar fibers gradually become longer and soft (widest). The motion of the basilar membrane is generally described as a travelling wave. The parameters of the membrane (stiffness, narrow, wide) at a given point along its length determine its characteristic frequency at which it is most sensitive to sound vibrations. High frequency sounds localize near the base of the cochlea (near the round and oval windows), while low frequency sounds localize near the apex (helicotrema); and the middle frequency sounds – middle part of helix.

There is a 50% hearing loss in the low frequency range; that means there is damage near the apex (helicotrema).

38. Anatomical dead space is the portion of the  air that  is left in the  airways  after expiration. The reduction of the anatomical dead space is typical for the following situation:

Explanation

Anatomical dead space extends from nose up to terminal bronchiole. It includes nose, pharynx, trachea, bronchi and branches of bronchi up to terminal bronchioles. These structures serve only as the passage for air movement. Gaseous exchange does not take place in these structures.

Tracheostomy is a surgical procedure that creates an opening through the neck into the trachea (wind pipe). A tube is usually placed through this opening to provide an airway and to remove secretions from the lungs. This tube is called a tracheostomy tube. This procedure is usually performed when there is a large object blocking the airway; inability to breathe on your own; severe neck or mouth injuries etc. This reduces the anatomical dead space because it cuts out the nose and pharynx from the anatomical dead space.

39.

Analysis of the experimental spirogram  of a 55-year-old  person  revealed a decrease in tidal volume and respiratory amplitude compared to  the  situation   of ten  years  ago. The  change  in these  indicators is caused by:

 

Explanation

Tidal volume is the volume of air breathed in and out of lungs in a single normal quiet respiration. Tidal volume signifies the normal depth of breathing. This volume and respiratory amplitude is dependent primarily on the contraction and relaxation of the diaphragm (diaphragm - primary respiratory muscle). So, a decrease in this parameters equally means a decrease in force of respiratory muscle contraction.

40.

A 60 year old patient has impaired perception of high-frequency sounds. These changes were caused by damage of the following auditory analyzer structures:

Explanation

FullSizeRender (26)FullSizeRender (25)

Two membranes divide the spiral canal of cochlea into 3 compartments – vestibular and basilar membrane. Along the basilar membrane are 20,000-30,000 tiny fibers called basilar fibers. Each fiber has different size and shape. Fibers near the oval window (base) are short and stiff (narrowest), while approaching towards helicotrema (apex), the basilar fibers gradually become longer and soft (widest). The motion of the basilar membrane is generally described as a travelling wave. The parameters of the membrane (stiffness, narrow, wide) at a given point along its length determine its characteristic frequency at which it is most sensitive to sound vibrations. High frequency sounds localize near the base of the cochlea (near the round and oval windows), while low frequency sounds localize near the apex (helicotrema); and the middle frequency sounds – middle part of helix.

There is an impaired perception of high frequency sounds; that means there is damage near the base of cochlea (i.e. near the round and oval windows).

41. Students who are taking examinations often have dry mouth.   The mechanism that causes this state is the realization of the following reflexes:

Explanation

Reflex activity is the response to a peripheral nervous stimulation that occurs without our consciousness. It can be:

* Inborn or unconditioned: present from birth, does not require previous learning or training.

* Acquired or conditioned: developed after conditioning or training. Acquired after birth.

It is conditioned because the students have had a previous experience with examinations before. The manifestation of dry mouth is a sympathetic effect.

image

42.

The temperature of the ambient environment is 38oC and relative air humidity is 50%. What ways of heat emission provide maintaining a constant temperature of the human body?

Explanation

Evaporation is a way the body dissipates heat to the environment by its evaporation via sweat or evaporation of moisture from the skin and respiratory tract mucous membranes of (“wet” heat loss). Evaporation closely related to relative humidity.

Heat Radiation is a way the surface of the human body emits heat to the environment in the form of infrared rays. The amount of heat the body radiates to the environment is proportional to the surface of radiation area and to the difference between the mean values of skin and environment temperature. The surface radiation area is the total surface area of body parts that contact the air. Elimination of heat by radiation increases with a decrease in ambient temperature and decreases with its increase. It is possible to reduce elimination of heat by radiation via reduction of the surface of radiation area (“winding oneself into a ball”). Heat radiation does not require a medium for transfer of heat. (Key words: naked or lightly clothed).

Convection is a way the body eliminates heat by means of transferring heat via moving particles of air or water. To dissipate heat by means of convection, body surface shall be airflowed at a temperature that is lower than the temperature of the skin. At that, air layer contacting with the skin warms up, decreases its density, rises and is replaced by cooler, denser air. By increasing the speed of the air flow (wind, ventilation) heat emission increases significantly as well (forced convection). Convection requires convection current; current of gases or liquids (Key words: air over exposed area of skin).

Conduction is a way the body eliminates heat by means of direct contact with another object. Heat is transferred down the temperature gradient (i.e. from the object of higher temperature to the object of lower temperature). Conduction requires contact with another object (Key words:  in water).

43. A 30 year old woman has subnormal concentration of  enzymes  in  the pancreatic juice. This might be caused by the hyposecretion of the following gastrointestinal hormone:

Explanation

image

·        Cholecystokinin-pancreozymin: source – I cells in duodenum and jejunum of small intestine. Action – increase pancreatic secretion, gallbladder contraction, sphincter of oddi relaxation and decrease gastric emptying. It acts on neural muscarinic pathways to cause pancreatic secretion.

·        Somastostatin: source – D cells (pancreatic islets, gastrointestinal mucosa). Action – decrease gastric acid and pepsinogen secretion; decrease pancreatic and small intestine fluid secretion; decrease gallbladder contraction; decrease insulin and glucagon release.

·        Secretin: source – S cells (duodenum). Action – increase pancreatic HCO3- secretion ( ↑ bicarbonate secretion); increase bile secretion; decrease gastric acid secretion.

·        GIP: source - K cells in duodenum and jejunum. Action – exocrine action: decrease gastric hydrogen ion (H+) secretion; endocrine action: increase insulin release. It is also known as Glucose-dependent insulinotropic peptide.

·        VIP: parasympathetic ganglia in sphincters, gallbladder, small intestine. Action – increase intestinal water and electrolyte secretion, relaxation of intestinal smooth muscle and sphincters.

Only cholecystokinin-pancreozymin increase pancreatic secretion. Secretin only increases pancreatic HCO3- secretion which neutralizes gastric acid in duodenum, allowing pancreatic enzymes to function.

44. A month   after surgical constriction of rabbit’s renal artery the considerable increase of systematic arterial  pressure was observed. What of the following regulation mechanisms caused the animal’s pressure change?

Explanation

FullSizeRender (12)

↓blood supply (surgical constriction) → activates renin. Renin catalyzes the conversion of angiotensinogen to angiotensin I. Angiotensin converting enzyme (ACE) converts angiotensin I → angiotensin II. Angiotensin II causes:

- vasoconstriction → ↑BP

- vasopressin (ADH) → ↑H2O reabsorption → ↑plasma volume

- aldosterone → ↑Na+ and H2O reabsorption → ↑plasma volume → ↑BP

45. A sportsman was examined after an intensive physical activity. The examination revealed disorder of movement coordination but the force of muscle  contractions remained the same. It can be explained by retarded speed of excitement conduction through:

Explanation

       One of the properties of synapse is fatigue. During continuous muscular activity, synapse becomes the seat of fatigue along with Betz cells present in motor area of frontal lobe of cerebral cortex. Fatigue at synapse is due to the depletion of neurotransmitter substance, acetylcholine. Depletion of acetylcholine occurs because of 2 factors:

·        Soon after the action, acetylcholine is destroyed by acetylcholinesterase.

·        Due to continuous action, new acetylcholine is not synthesized.

The excitatory terminals on many neurons can store enough excitatory transmitter substance to cause only about 10,000 action potentials and the neurotransmitter can be exhausted in only a few seconds to a few minutes of rapid stimulation.

            It is fatigue of central synapses because only the function of muscle   coordination is affected which is an exclusive function of the higher brain centers. Force of contraction s determined by discharge at neuromuscular synapses in the neuromuscular junction.

46.

After     a    long    training     session a sportsman has developed fatigue accompanied by abrupt performance decrement. What link  of the  reflex  arch was the fatigue initiated  in?

Explanation

Reflex arch is the anatomical nervous pathway for a reflex action. A simple reflex arc has 5 components:

·        Receptor: end organ, which receives the stimulus.

·        Afferent nerve or sensory nerve: transmits sensory impulses from the receptor to center.

·        Center: receives the sensory impulses via afferent nerve fibers and in turn, it generates appropriate motor impulses. Center is located in the brain or spinal cord.

·        Efferent nerve or motor nerve: transmits motor impulses from the center to the effector organ.

·        Effector organ: is the structure such as muscle or gland where the activity occurs in response to stimulus.

When a reflex activity is continuously elicited for a long time (long training session), the response is reduced slowly and at one stage, the response does not occur. This stage of failure to give response to the stimulus is called fatigue. Center or the synapse of the reflex arc is the first seat of fatigue.

47.

Blood minute volume of a 30 year old woman at rest is 5 l/m. What blood volume is pumped through the pulmonary vessels per minute?

Explanation

Blood minute volume is the amount of blood pumped out by each ventricle in one minute. It is the product of stroke volume and heart rate. Normal value is 5L/ventricle/minute.

If blood minute volume is 5L/m; the volume pumped through the pulmonary vessels (lung vessels) per minute by the right ventricle equals 5L.

48.

A patient under test was subjected to a moderate physical stress. His minute blood volume amounted 10 l/min.  What blood volume was pumped   through his lung vessels every minute?

Explanation

Blood minute volume is the amount of blood pumped out by each ventricle in one minute. It is the product of stroke volume and heart rate. Normal value is 5L/ventricle/minute.

If blood minute volume is 10L/m; the volume pumped through the pulmonary vessels (lung vessels) per minute by the right ventricle equals 10L.

49.

Parodontitis is treated with  calcium preparations and a hormone that stimulates  tooth  mineralization and inhibits tissue resorption. What hormone is it?

Explanation

image

Calcitonin is secreted by parafollicular cells (C cells of the thyroid gland). It ↓bone resorption of Ca2+ (i.e. it inhibits tissue resorption). It opposes actions of parathyroid hormone. But it is not important in normal Ca2+ homeostasis.

Parathyroid hormone: secreted by chief cells of parathyroid gland. Effects include:

↑bone resorption of Ca2+ and PO43- → ↑their plasma levels

↑kidney reabsorption of Ca2+ in distal convoluted tubule → ↑ Ca2+ plasma level

↓reabsorption of PO43- in proximal convoluted tubule → ↓ PO43- plasma levels

↑Calcitriol (vit D3) production by stimulating kidney 1α-hydroxylase in proximal convoluted tubule. It increases Ca2+ and PO43- absorption in the intestine.

In general, parathyroid hormone ↑ Ca2+ plasma level but ↓ PO43- plasma levels. Abnormal synthesis (↑synthesis) of parathyroid hormone can lead to hypercalcemia and hypophosphatemia.

Calcitriol ↑ circulating Ca2+ ions as a means of enhancing intestinal absorption of calcium (NB: Calcitriol production is dependent on parathyroid hormone).
50.

A man who is riding the carousel presents with increased heart rate, sweating, nausea.  This condition is caused primarily by the stimulation of the following receptors:

Explanation

image     

The receptor areas of the vestibular labyrinth are represented with the following structures:

·        Macula of Utricle

·        Macula of Saccule

·        Ampullary crests

The first two detect linear motion, while the ampullary crest detect angular motion. The vestibulocochlear nerve supply these receptors. Both maculae consist of the sensory hair cells covered with jelly-like susbstance. The substance contains the crystals of calcium carbonate called otoliths (vestibular otolith). The utricle and saccule detect linear movement, also contributing to balance. The ampullary crests reside within each membranous ampulla. They also comprise the sensory hair cells covered with the same jelly-like substance called the ampullary cupula. The ampullae is the sensory organ in the semicircular canal that sense angular (rotational) acceleration of the head, thereby regulating balance. NB: carousel is a revolving belt.

51.

Atria of an experimental animal were superdistended by blood that  resulted in decreased reabsorption of Na+ and water in renal tubules.  This can be explained by the influence of the following factor upon kidneys:

Explanation

Atrial natriuretic peptide is secreted in response to increase atrial pressure. It causes increase glomerular filtration rate (GFR) and increase sodium ion filtration with no compensatory sodium ion reabsorption and water in distal nephron which leads to increase diuresis.

Antidiuretic hormone (vasopressin) is secreted in response to decrease blood volume and increase plasma osmolarity. It binds to receptors on principal cells of collecting ductules causing increase number of aquaporins and increase water reabsorption which leads to decreased diuresis.
52.

Power inputs of a man were measured. In what state was this man if his power inputs were lower than basal metabolism?

Explanation

     Sleep is the natural periodic state of rest for mind and body with closed eyes characterized by partial or complete loss of consciousness. Sleep is unconsciousness from which the person can be aroused by sensory or other stimuli. It is to be distinguished from coma, which is unconsciousness from which the person cannot be aroused. During sleep, most of the body functions are reduced to basal level or even below the basal level. Therefore, power inputs can be lower than basal level during sleep. Unlike rest where it remains at the basal level or higher.

53.

A  man  is  being  measured  power inputs  on an empty  stomach,  in the lying position,  under  conditions of physical and psychic rest at a comfortable temperature. Power inputs will reach the maximum at:

Explanation

     5-6pm

54.

When   measuring   power   inputs   of a man by the  method of indirect  calorimetry the following results were obtained: 1000 ml oxygen consumption and 800 ml carbon  dioxide liberation per minute.  The man under examination has the following respiratory coefficient:

Explanation

RQ = vCO2 ÷ vO2 = 800 ÷ 1000 (ml) = 0.8

Minute O2 uptake – 1000ml

    Minute CO2 emission – 800ml

    Respiratory Quotient (RQ) = vCO2 /vO2 = 800/1000(ml) = 0.8

   

55.

As a result of damage to certain structures of brainstem an animal lost orientation reflexes.  What   structures were damaged?

Explanation

     Quadritubercular bodies/tectal plate is the dorsal portion of the midbrain comprises 4 colliculi – two superior and two inferior. The nuclei of colliculi are responsible for reflexes associated with sudden sound and visual stimuli (auditory and visual orientative reflexes); they also maintain consciousness. The nuclei give rise to the tectospinal tract. Superior colliculi – visual orientative reflex; Inferior colliculi – auditory orientative reflex.

56. Emotional stress causes activation of hormone-sensitive triglyceride lipase in the adipocytes.  What secondary mediator takes part in this process?  

Explanation

The mobilization of stored fat requires the hydrolytic release of fatty acids and glycerol from their triacylglycerol (TAG) form. This process is initiated by hormone-sensitive lipase, which removes a fatty acid from carbon 1 and/or carbon 3 of the TAG. This enzyme is activated when phosphorylated by cyclic AMP (cAMP)-dependent protein kinase. cAMP is produced in the adipocyte when one of several hormones (such as epinephrine or glucagon – stress hormones) binds to receptors on the cell membrane and activates adenylyl cyclase.

57. An isolated  cell of human  heart automatically generates excitement impulses  with frequency of 60 times  per minute. This cell was taken from the following heart  structure:

Explanation

The sinoatrial (SA) node is a small strip of modified cardiac muscle, situated in the superior part of lateral wall of right atrium, just below the opening of superior vena cava. The fibers of this node do not have contractile elements. SA node is called the pacemaker because the rate of production of impulse (rhythmicity) is higher in SA node than in other parts. The rate is 60-100/min and higher during tachycardia when stimulated by sympathetic effects. Atrioventricular (AV) node is 40-60/min.

58.

During  influenza  epidemic  40%  of pupils  who  didnt go  in  for  sports  were affected  by  the  disease,  and  among  the pupils who regularly did physical exercises this index  was only 20%. What  adaptative mechanisms  determined such a low sicknesrate  of pupils  participating in the sports?

Explanation

59. A  60  year  old  patient  was  found to  have  a  dysfunction   of  main  digestive enzyme  of saliva. This  causes  the  disturbance of primary hydrolysis of:

Explanation

Saliva contains two major types of protein secretion:

·        A serous secretion that contains ptyalin (α-amylase or salivary amylase), an enzyme for digesting starches.

·        Mucus secretion that contains mucin for lubricating and for surface protective purposes.

Salivary amylase is a carbohydrate-digesting (amylolytic) enzyme. It acts on cooked or boiled starch and converts it into dextrin and maltose. Though starch digestion starts in the mouth, major part of it occurs in stomach because food stays only for a short time in the mouth. Optimum pH necessary for the activation of salivary amylase is 6. Salivary amylase cannot act on cellulose.

60. When  water  affects  mucous membrane of the inferior  nasal meatuses, this causes \\\"diver reflex\\\" that provokes:

Explanation

When water or any irritating noxious vapors or gases affects the mucus membrane of the nose, an involuntary temporary arrest of breathing (apnea) develops. This is a protective reflex to prevent the subject from inhaling harmful substances (reflectory apnea – reflex apnea).

61.

Microelectrode  technique  allowed to register a potential following \"all-or-none\" law and being able of undecremental spreading.  Specify this potential:

Explanation

Action potential is a series of electrical changes that occur in the membrane potential when the muscle or nerve is stimulated. It occurs in 2 phases: depolarization and repolarization. Excitable tissues obey the all-or-none law which states that when an excitable tissue is stimulated by a stimulus, it gives maximum response or does not give any response at all. Below the threshold level i.e. if the strength of stimulus is not adequate, the tissue does not give any response. Action potential obeys the all-or-none law because a particular threshold must be reached for an action potential to occur.

62.

A patient got an injury of spinal marrow   in  a  road  accident   that  caused loss of tactile sensation,  posture sense, vibration sense. What conduction tracts are damaged?

 

Explanation

Fasciculus gracilis (tract of Goll) and Fasciculus cuneatus (tract of Burdach): fasciculus gracilis and cuneatus are together called ascending posterior column tracts. These tracts are formed by the fibers from posterior root ganglia. Thus, both tracts are constituted by the fibers of first order neurons of sensory pathway. Functions: fine (epicritic) tactile sensation; tactile localization; tactile discrimination; sensation of vibration; conscious kinesthetic sensation; stereognosis (ability to recognize the known objects by touch with closed eyes).

Fasciculus gracilis contains the fibers from lower extremities and lower parts of the body. Fasciculus cuneatus contains fibers from upper part of the body.

63. A  doctor  asked  a patient to  breath out  fully  after  taking  a  normal   breath. What muscles contract during such exhalation?

Explanation

All muscles that elevate the rib cage are muscles of inspiration and those that depress the rib cage are muscles of expiration.

Muscles of inspiration:

·        Sternocleidomastoid: lift upward on the sternum.

·        Anterior serrati: lift many of the ribs.

·        Scalene: lift the first two ribs.

Muscles of expiration: Abdominal recti – pull down the lower ribs and other abdominal muscles also compress the abdominal contents upwards against the diaphragm and internal intercostals.

Normal respiration is accomplished by the movement of the diaphragm only.

64.

One  of  sections  of  central  nervous system has layerwise arrangement of neurocytes. Among  them  there  are  cells of the  following forms: stellate,  fusiform, horizontal, pyramidal. What section of central  nervous  system is this structure typical for?

Explanation

image

Cerebral cortex consists of gray mater that surrounds the deeper white mater. The cerebral cortex is formed by 6 layers of structures:

·        Molecular or plexiform layer or horizontal layer ( contains horizontal cells of cajal).

·        External granular/stellate layer

·        Outer pyramidal layer

·        Internal granular/stellate layer

·        Internal pyramidal layer

·        Fusiform cell layer

Layers of grey mater in cerebellum:

·        Outer molecular or plexiform layer

·        Intermediate purkinje layer

·        Inner granular layer

65. An aged man had raise of arterial pressure under  a stress. It was caused  by activation of:

Explanation

imageimage     

Stress activates the sympathoadrenal system and the hypothalamic-pituitary-adrenocortical (HPA) axis. Defense reactions involve catecholamine release, vagal withdrawal, cortisol secretion and activation of the rennin-angiotensin system. Catecholamine release is capable of increasing the arterial pressure. Sympathoadrenal system involves the sympathetic nervous system and the adrenal glands especially increased sympathetic activity that causes increased secretion of epinephrine by the adrenal medulla and norepinephrine by the postganglionic sympathetic nerve endings.

66.

A 30-year-old  male patient with acute pancreatitis has been found to have a disorder   of   cavitary   protein  digestion. The reason  for such condition can be the hyposynthesis  and  hyposecretion of  the following enzyme:

 

Explanation

Acute pancreatitis → ↓production of pancreatic juice.  Acute pancreatitis is an autodigestion of pancreas by pancreatic enzymes (proteolytic enzymes).

Trypsin is the most powerful proteolytic enzyme in pancreatic juice. Pepsin is secreted by chief cells in the stomach.

67. During  preparation of a patient to a heart  surgery it was necessary  to measure pressure  in  heart   chambers.  In  one   of them  pressure varied  from  0 mm Hg up to  120 mm  Hg  within  one  cardiac  cycle. What heart  chamber is it?

Explanation

     Pressure in each heart chambers:

 

    Diastole (mmHg)

      Systole (mmHg)

Left ventricle

               4-12

            90-140

Right ventricle

               0-8

             15-28

Left atrium

          -2 to +6

               6-20

Right atrium

          -2 to +6

               2-14

Only the left ventricle can range from 0-120mmHg

68.

Lung   ventilation   in   a   person    is increased   as  a  result  of  physical  activity. Which  of the  following  indices  of the external  respiration is much  higher  than in a state of rest?

Explanation

     During physical activity all lung volumes tend to increase to meet up with the increased demand. Therefore, the whole respiratory volume is increased – inspiratory reserve volume, expiratory reserve volume, tidal volume; vital capacity includes inspiratory reserve volume, tidal volume and expiratory reserve volume. Total lung capacity is the volume of air present in lungs after a deep (maximal) inspiration.

69.

As  a  result  of  activation   of  the  ion channels  of  the  external membrane the rest   potential  of  an  excitable   cell  has greatly increased. What channels were activated?

Explanation

    Increase in rest potential of an excitable cell is hyperpolarization. Hyperpolarization is often caused by efflux of K+ (a cation) through K+-channels or influx of Cl- (an anion) through Cl- channels. Hyperpolarization is the opposite of depolarization. Influx of Na+ or Ca2+ causes depolarization. Depolarization decreases rest potential.

70. Which  way  of  heat  emission  by  the bodies  of greenhouse workers  is the most effective   at   the   temperature  of   36oC degrees and relative humidity of 70%?

Explanation

Evaporation is a way the body dissipates heat to the environment by its evaporation via sweat or evaporation of moisture from the skin and respiratory tract mucous membranes of (“wet” heat loss). Evaporation closely related to relative humidity.

Heat Radiation is a way the surface of the human body emits heat to the environment in the form of infrared rays. The amount of heat the body radiates to the environment is proportional to the surface of radiation area and to the difference between the mean values of skin and environment temperature. The surface radiation area is the total surface area of body parts that contact the air. Elimination of heat by radiation increases with a decrease in ambient temperature and decreases with its increase. It is possible to reduce elimination of heat by radiation via reduction of the surface of radiation area (“winding oneself into a ball”). Heat radiation does not require a medium for transfer of heat. (Key words: naked or lightly clothed).

Convection is a way the body eliminates heat by means of transferring heat via moving particles of air or water. To dissipate heat by means of convection, body surface shall be airflowed at a temperature that is lower than the temperature of the skin. At that, air layer contacting with the skin warms up, decreases its density, rises and is replaced by cooler, denser air. By increasing the speed of the air flow (wind, ventilation) heat emission increases significantly as well (forced convection). Convection requires convection current; current of gases or liquids (Key words: air over exposed area of skin).

Conduction is a way the body eliminates heat by means of direct contact with another object. Heat is transferred down the temperature gradient (i.e. from the object of higher temperature to the object of lower temperature). Conduction requires contact with another object (Key words:  in water).

71.

A 35-year-old patient complains about having  severe  rhinitis  and  loss  of  sense of smell for a week. Objectively: the nasal cavity contains a lot of mucus covering the mucous membrane and blocking olfactory receptors. In what region of the nasal cavity are these receptors located?

 

Explanation

     Olfactory receptors are situated in olfactory mucus membrane, which is the modified mucus membrane that lines upper part of nostril (superior nasal concha). Olfactory receptor cell is a bipolar neuron. Dendrite of this neuron is short and it has an expanded end called olfactory rod. From the olfactory rod, about 10-12 cilia arise. These cilia project to the surface of olfactory mucus membrane in the upper part of nostril. Mucus secreted by Bowman glands continuously lines the olfactory mucosa.

72. During  fighting a man had a cardiac arrest  as a result  of a hard  blow  to  the upper  region  of anterior abdominal wall. Which of the described  mechanisms might have provoked the cardiac arrest?

Explanation

Reflex activity is the response to a peripheral nervous stimulation that occurs without our consciousness. It can be:

* Inborn or unconditioned: present from birth, does not require previous learning or training.

* Acquired or conditioned: developed after conditioning or training. Acquired after birth.

Aschner’s reflex: press on the eyeball produces parasympathetic effects.Goltz’ reflex: by pressing/strong blow to the epigastric region produces similar parasympathetic responses. They are parasympathetic reflexes and because no prior learning is involved – it is an unconditioned reflex.

73.

There  is a severe time restriction for people’s  staying  at  a height  of over  800 m  above   the  sea  level  without   oxygen bombs.  What  is the  life limiting factor  in this case?

Explanation

     Although the percentage of oxygen in inspired air is constant at different altitudes; the fall in atmospheric pressure at higher altitudes decreases the partial pressure of inspired oxygen and the driving pressure for gas exchange in the lungs. A fall in inspired oxygen pressure reduces the driving pressure for gas exchange in the lungs and in turn produces a cascade of effects right down to the level of the mitochondria, the final destination of the oxygen. Partial pressure is used to describe a mixture of gases. It’s a way of describing how much of a gas is present. It is the pressure that any one gas would exert on the walls of the container if it were the only gas present.

74.

During  an  experiment the  myotatic reflex has been studied in frogs. After extension in  a  skeletal  muscle  its reflectory contraction was absent. The reason  for  it  might  be  a  dysfunction   of the following receptors:

Explanation

     Muscle spindle s a spindle shaped proprioceptor situated in the skeletal muscle. It is formed by modified skeletal muscle fibers called intrafusal muscle fibers. Muscle spindle gives response to change in the length of the muscle. It detects how much the muscle is being stretched and sends this information to the CNS via sensory nerve fibers. Stimulation of muscle spindle elicits the stretch reflex. Extensor muscles, particularly the antigravity muscles exhibit a severe and prolonged contraction during stretch reflex. Stretch reflex is the reflex contraction of muscle when it is stretched. Also called myotatic or a monosynaptic reflex. It is the quickest of all the reflexes.

75.

After  a craniocerebral trauma a patient lost the ability to execute learned purposeful movements (apraxia). The injury is most likely localized in the following region of the cerebral cortex:

 

Explanation

     Apraxia is defined as a cognitive motor disorder in which the patient loses the ability to accurately perform learned, skilled actions. Apraxia is primarily a condition that localized to the dominant (usually left) hemisphere of the brain. In particular, lesions of supramarginal gyrus and underlying white matter of the left parietal lobe have been implicated to cause apraxia.

76.

Tissue inosytol triphosphates are generated as  a  result  of  the  phosphatidylinositol   diphosphate  hydrolysis   and act  as  secondary   agents   (mediators)  in the  mechanism  of hormone action.  Their effect in cells is directed at:

Explanation

     The protein hormones and catecholamines which act on a target cell are called first messenger. It combines with the receptor and forms hormone-receptor complex. Hormone-receptor complex activates the enzymes of the cell and cause the formation of the second messenger. The second messenger produces the effects of the first messenger inside the cell. Most common second messenger is cAMP; others are Ca2+ and calmodulin; inositol triphosphate; cGMP and diacylglycerol (DAG).

       Inositol triphosphate (IP3) is formed from phosphotidylinositol biphosphate (PIP3). Hormone-receptor complex activates the enzyme phospholipase which convert PIP2 into IP3. IP3 acts on protein kinase C and causes the physiological response by the release of calcium ions into the cytoplasm of target cell.

77.

A    newborn   develops    dyspepsia after   the   milk  feeding.   When   the   milk is substituted by the  glucose  solution the  dyspepsia  symptoms  disappear. The newborn  has the subnormal activity of the following enzyme:

Explanation

    Lactase (β-galactosidase) cleaves lactose (in milk) producing galactose and glucose. Hereditary deficiencies of lactase have been reported in infants and children with dissacharide intolerance. Treatment for this disorder is to reduce consumption of milk. This is seen when the milk is substituted by glucose solution.

78.

A  man  having  a  hearing  loss  after a head trauma was delivered to the neurosurgery department.  The  cause  of the  hearing  loss might  be the  damage  of the following lobe of cerebral cortex:

Explanation

   IMG_9921

 Temporal lobe of cerebral cortex includes 3 functional areas: primary auditory area, secondary auditory area and the area for equilibrium. The primary auditory area is concerned with perception of auditory impulses, analysis of pitch, determination of intensity and source of sound. Therefore, damage to this lobe of cerebral cortex can cause hearing loss.

79. Which muscle contraction will be observed  in  the   upper   extremity  during holding  (but  not  moving)  a load  in a certain position?

Explanation

     Muscle contraction is classified into 2 types: Isotonic and Isometric.

·        Isotonic contraction: the tension in the muscle remains the same but the length of the muscle fiber is changing (Iso = same; tonic = tension) e.g. simple flexion of arm, where shortening of muscle fibers occurs but the tension does not change.

·        Isometric contraction: the length of muscle fibers remains the same but the tension is increased e.g. pulling any heavy object when the muscles become stiff and strained with increased tension but the length does not change. Holding (but not moving) – length does not change.

80. A patient consulted  a doctor  about  a sensation of  imbalance  which  appeared after a trauma. Which nerve is damaged?

Explanation

imageimage    

The receptor areas of the vestibular labyrinth are represented with the following structures:

·        Macula of Utricle

·        Macula of Saccule

·        Ampullary crests

The first two detect linear motion, while the ampullary crest detect angular motion. The vestibulocochlear nerve supply these receptors. Both maculae consist of the sensory hair cells covered with jelly-like susbstance. The substance contains the crystals of calcium carbonate called otoliths (vestibular otolith). The utricle and saccule detect linear movement, also contributing to balance. The ampullary crests reside within each membranous ampulla. They also comprise the sensory hair cells covered with the same jelly-like substance called the ampullary cupula. The ampullae is the sensory organ in the semicircular canal that sense angular (rotational) acceleration of the head, thereby regulating balance.
81. During    an   experiment  a   skeletal muscle is stimulated by a series of electric impulses.  What  type  of muscle  contraction  will be  observed   provided   that  each subsequent  impulse   comes  in  the  period  of  shortening of  the  previous  single muscle contraction?

Explanation

krushkrok No21 (2010)

Tetanus is defined as the sustained contraction of muscle due to repeated stimuli with high frequency. When the multiple stimuli are applied at a higher frequency in such a way that the successive stimuli fall during contraction period (period of shortening) of previous twitch, the muscle remains in state of tetanus. While increasing the frequency, fusion of contractions increases every time and finally complete tetanus occurs. Holotetanus – complete tetanus.

When the frequency of stimuli is not sufficient to cause tetanus, the fusion of contractions is not complete and then we have – incomplete/partial/waved tetanus. This occurs (i.e. the next stimuli occurs) during the period  of relaxation.

82.

ECG  of a patient shows prolongation of T-wave. This is caused  by deceleration in ventricles of:

Explanation

krushkrok No28 (2009)krushkrok No28a (2009)   

 ‘T’ wave is the final  ventricular complex and is a positive wave. It is due to the repolarization of ventricular musculature. Normal duration is 0.2sec; normal amplitude is 0.3mV.

83.

A  newborn  child  suffers  from  milk curdling in stomach, this means that soluble  milk proteins (caseins)  transform to   insoluble   proteins    (paracaseins)  by means   of   calcium   ions   and   a  certain enzyme.  What  enzyme  takes  part  in this process?

Explanation

The enzymatic components of gastric juice of the child is similar to the component of the adult person, however, it considerably differs according to age. After the birth of the child, the gastric juice is secreted in very little amount (about 20ml) and its acidity is low, the splitting of protein by pepsin is absent. It gradually develops up to the end of the first year of life when pH decreases (i.e. ↑acidity). However, the splitting of protein in the stomach appreciably occurs. It is promoted by the enzyme called rennin, which curdles milk into fine flakes. Rennin operates the best way in poorly acidic environment (pH 6 – 6.5), but it can also function in neutral and weak alkaline environment.

NB: Renin – kidney;  Rennin – stomach

84. Histological examination of a 40 year old man’s thymus revealed  reduced share of parenchymatous elements, increased share  of adipose  and loose connective tissue, its enrichment with thymus  bodies. The organ’s mass was unchanged. What is this phenomenon called?

Explanation

There is a certain correlation between age of individual and thymus activity. In neonates, it already appears to have a considerable mass of 13.3g on the average. Most intensive growth occurs during first 3years of life, when the gland doubles in size. Having reached the maximum weight (about 26 – 30g), the thymus retains it until 20 years of life. After 20 years of age, the thymus parenchyma experiences gradual involution and is substituted with fat tissue. After 50 years of age, the fat constitutes 90% of gland mass.

85.

People  adapted to high external temperatures  have  such  peculiarity: profuse   sweating   isn’t  accompanied  by loss of large volumes  of sodium  chloride. This is caused by the effect of the following hormone upon the perspiratory glands:

 

Explanation

Aldosterone produced in adrenal cortex (zona glomerulosa): causes increased sodium (Na+) reabsorption; increased potassium and hydrogen ions (↑K+, H+) excretion. They increase sodium (↑Na+) channel and Na+ /K+-pump insertion in principal cells of collecting duct; enhances K+ and H+ excretion by way of principal cell K+ channels and α-intercalated cell H+ ATPases of collecting duct. Therefore, increase in aldosterone → ↑ K+ in urine (excretion) and ↓ Na+ in urine (↑ reabsorption); And decreased aldosterone → ↓ K+ excretion (↓K+ in urine) and ↓ Na+  reabsorption (i.e. ↑Na+ in urine); same effects on sweats glands too.

This is an adaptative mechanism causing increased aldosterone secretion which leads to decreased sodium ion excretion in sweat, due to the fact that increased aldosterone leads to increased reabsorption of sodium.

86. After  destruction of  CNS  structures an animal  lost orientative reflexes.  What structure was destroyed?

Explanation

     Quadritubercular bodies/tectal plate is the dorsal portion of the midbrain comprises 4 colliculi – two superior and two inferior. The nuclei of colliculi are responsible for reflexes associated with sudden sound and visual stimuli (auditory and visual orientative reflexes); they also maintain consciousness. The nuclei give rise to the tectospinal tract. Superior colliculi – visual orientative reflex; Inferior colliculi – auditory orientative reflex.

87.

A  patient staggers  and  walks astraddle. He  has  hypomyotonia of arm and leg muscles, staccato  speech.  In what brain section is this affection localized?

Explanation

During cerebellar lesions, there  are disturbances in posture, equilibrium and movements. Disturbances in movements: ataxia, asynergia, asthenia (weak muscle contractions with characteristically rapid onset of muscle fatigue), Dysmetria, Intention tremor, astasia (loss of the capacity for sustained tetanic contractions), nystagmus, rebound phenomenon, dysarthria, adiadochokinesis, atonia (lack or impairment of muscle tone).

88.

Vagus branches that  innervate heart are  being  stimulated  during   an  experiment.  This caused reduction of heart  rate due  to  the  intensification of the  following process (through the cell membrane of cardiac pacemaker):

Explanation

Vagus nerve branches that innervate the heart produce parasympathetic effects on heart’s function e.g. ↓heart rate, force of contraction etc. This is as a result of hyperpolarization of the pacemaker cells. Hyperpolarization is as a result of K+ efflux (K+ yield) making it take a longer time for the cell to reach the threshold potential. This delay in reaching the threshold produces the delay or decrease in heart rate.

89. Voluntary breath-holding caused increase   of  respiration  depth   and frequency.   The   main  factor   stimulating these changes of external  respiration is:

Explanation

Central chemoreceptors are responsible for 70 – 80% of increased ventilation through chemical regulatory mechanism. Main stimulant for central chemoreceptors is the increased hydrogen ion concentration. However, if H+ concentration increases in blood, it cannot cross the blood-brain barrier and blood-cerebrospinal fluid barrier. On the other hand, if CO2 increases in the blood, it can easily cross the blood-brain barrier and blood-CSF barrier and enter the interstitial fluid of brain or the CSF. There, the CO2 combines with water to form carbonic acid. Since carbonic acid (H2CO3) is unstable, it immediately dissociates into H+ and bicarbonate ion. 

Then H+ stimulates the central chemoreceptors. From chemoreceptors, the excitatory impulses are sent to dorsal respiratory group of neurons, resulting in increased ventilation (increased rate and force of breathing). Lack of O2 does not have significant effect on the central chemoreceptors, except that it generally depresses the overall function of brain.

90. Surface  with an intact toad  on it was inclined to the right. Tone of extensor muscles  became  reflectory  higher  due  to the activation  of the following receptors:

Explanation

     The receptor areas of the vestibular labyrinth are represented with the following structures:

·        Macula of Utricle

·        Macula of Saccule

·        Ampullary crests

The first two detect linear motion, while the ampullary crest detect angular motion. The vestibulocochlear nerve supply these receptors. Both maculae consist of the sensory hair cells covered with jelly-like susbstance. The substance contains the crystals of calcium carbonate called otoliths (vestibular otolith). The utricle and saccule detect linear movement, also contributing to balance. The ampullary crests reside within each membranous ampulla. They also comprise the sensory hair cells covered with the same jelly-like substance called the ampullary cupula. The ampullae is the sensory organ in the semicircular canal that sense angular (rotational) acceleration of the head, thereby regulating balance.
91. A  patient got  a trauma that  caused dysfunction  of  motor   centres  regulating activity  of  head  muscles.  In  what  parts of cerebral cortex  is the respective centre normally localized?

Explanation

krushkrok No46a (2014)image

Primary motor area extends throughout the precentral gyrus and the adjoining lip of central sulcus. Areas 4 and 4S are present here. Muscles of various parts of the body are represented in area 4 in an inverted way from medial to lateral surface. Lower parts of the body are represented in the lateral (upper) surface and upper parts of the body are represented in the lateral (lower) surface. Order of representation from medial (superior, upper) to lateral (inferior, lower) surface: toes, ankle, knee, hip, trunk, shoulder, arm, elbow, wrist, hand, fingers and face. Area 4 is concerned with contraction of discrete muscles.

92.

A    patient   was    diagnosed   with paralysis of facial and masticatory muscles.  The   haematoma  is  inside  the genu of internal capsule. What conduction tract is damaged?

Explanation

image

The pyramidal fasciculus is subdivided into the corticonuclear/corticobulbar fibers and the corticospinal fibers. The fiber of the pyramidal fasciculus passes through the genu and the anterior portion of the internal capsule and descends to the brainstem and the spinal cord. The corticonuclear tract passes through the genu of the internal capsule.  The genu is situated between the anterior and posterior limbs. Lesion in genu causes alteration in motor activities in opposite side due to damage of corticonuclear/corticobulbar fibers.

93. A young woman who entered a production department where  it strongly smelt of paints and varnishes had a bronchospasm. This reflex was caused  by irritation of the following receptors:

Explanation

Irritant receptors are stimulated by irritant chemical agents. These receptors send afferent impulses to respiratory centers via vagal nerve fibers. Stimulation of irritant receptors produces reflex hyperventilation along with bronchospasm. Hyperventilation along with bronchospasm prevents further entry of harmful agents into the alveoli.

94. An isolated  muscle fiber is under examination. It  was established that  the threshold of stimulation force became  significantly lower. What is the cause of this phenomenon?

Explanation

During the onset of depolarization and voltage gated sodium channels open and there is slow influx of Na+. When depolarization reaches 7 – 10mV, the voltage gated Na+ channels start opening at a faster rate. It is called Na+ channel activation. When the firing level is reached, the influx of Na+ is very great and it leads to overshoot. The gradual influx of Na+ lowers the threshold of stimulation force.

95.

A patient consumed  a lot of reach in proteins  food that  caused increase  of rate of proteolytic enzymes of pancreatic juice. It is also accompanied by increase  of rate of the following enzyme:

Explanation

Major proteolytic enzymes of pancreatic juice are trypsin and chymotrypsin. Trypsin is the most powerful proteolytic enzyme. It is an endopeptidase and breaks the interior bonds of the protein molecules and converts proteins into proteoses and polypeptides.

96.

In course of an experiment thalamocortical tracts  of an animal  were cut. What type of sensory perception remained intact?

Explanation

Olfactory receptors (1st order neuron) → Mitral cells (2nd order neuron) → Olfactory tract → Olfactory trigone, anterior perforated substance, septum pellucidum (3rd order neuron) → Uncus of parahippocampal gyrus.

The Olfactroy analyzer is one of the oldest ones so it features several fibers that take the shortest route to the Olfactory cortex i.e. do not relay within the thalamus. Therefore cutting the  thalamocortical tracts will not affect olfactory stimulus transmission to the cerebral cortex.

Thalamocortical tracts transmits all sensory information to the cerebral cortex except the Olfactory stimulus. This  tract arise from different nuclei in the thalamus (i.e. the third order neuron) and ends in the cerebral cortex.

97.

An  infectious   disease  caused contractive activity  of  muscles  that contract   and  dilate  eye  pupil  (paralytic state). What functional eye system was damaged?

Explanation

The accommodation mechanism, that is, the mechanism that focuses the lens system of the eye – is essential for a high degree of visual acuity. Accommodation results from contraction or relaxation of the eye ciliary muscle. Contraction causes increased refractive power of the lens and relaxation causes decreased power. When viewing far (remote) objects, the ciliary muscle relaxes and the internal media exert a certain pressure on the layer. The ciliary zonule thus appears to be stretched, which in turn results in flattening of the lens because of radial stretching of its capsule. On the contrary, watching the close objects causes the ciliary muscle to contract and it pulls the ciliary body together with the entire vascular layer anteriorly. Circular fibers of the ciliary muscle narrow the opening (pupil) of the ciliary body where the lens is suspended. These two opposing processes are called accommodation. Paralytic state of this muscle will cause a disorder of accommodation.

98.

Brain tomography revealed  a tumour in the region of red nucleus. What part of brain is damaged?

 

Explanation

The midbrain comprises the tectal (quadrigeminal, quadritubercular) plate and the cerebral peduncles. Between them is the cerebral aqueduct. Each cerebral peduncle features the ventral portion called the base of peduncle and the dorsal portion called the tegmentum of midbrain. The red nucleus is localized in the tegmentum of midbrain. The red nucleus is one of the biggest nuclei of midbrain.

99. The temperature of the ambient environment is 38oC and relative  air humidity is 50%. What ways of heat emission provide maintaining a constant temperature of the human  body?

Explanation

Evaporation is a way the body dissipates heat to the environment by its evaporation via sweat or evaporation of moisture from the skin and respiratory tract mucous membranes of (“wet” heat loss). Evaporation closely related to relative humidity.

Heat Radiation is a way the surface of the human body emits heat to the environment in the form of infrared rays. The amount of heat the body radiates to the environment is proportional to the surface of radiation area and to the difference between the mean values of skin and environment temperature. The surface radiation area is the total surface area of body parts that contact the air. Elimination of heat by radiation increases with a decrease in ambient temperature and decreases with its increase. It is possible to reduce elimination of heat by radiation via reduction of the surface of radiation area (“winding oneself into a ball”). Heat radiation does not require a medium for transfer of heat. (Key words: naked or lightly clothed).

Convection is a way the body eliminates heat by means of transferring heat via moving particles of air or water. To dissipate heat by means of convection, body surface shall be airflowed at a temperature that is lower than the temperature of the skin. At that, air layer contacting with the skin warms up, decreases its density, rises and is replaced by cooler, denser air. By increasing the speed of the air flow (wind, ventilation) heat emission increases significantly as well (forced convection). Convection requires convection current; current of gases or liquids (Key words: air over exposed area of skin).

Conduction is a way the body eliminates heat by means of direct contact with another object. Heat is transferred down the temperature gradient (i.e. from the object of higher temperature to the object of lower temperature). Conduction requires contact with another object (Key words:  in water).

100.

A man has normal  sensitivity of his finger  skin,  however  he  doesn’t sense  his wedding ring around the finger. What process  induced   by  wearing  of  the  ring has caused this phenomenon?

Explanation

Adaptation is the decline in discharge of sensory impulses when a receptor is stimulated continuously with constant strength. It is also called sensory adaptation or desensitization. The ring has stimulated the receptors continuously with a constant strength for a long time and the receptors adapt.

101.

ECG  study  showed  that  the  T -waves were  positive  in  the  standard extremity leads, their  amplitude and  duration were normal.   The  right  conclusion   would  be that  the  following  process  runs  normally in the heart  ventricles:

Explanation

krushkrok No28 (2009)krushkrok No28a (2009)      

‘T’ wave is the final  ventricular complex and is a positive wave. It is due to the repolarization of ventricular musculature. Normal duration is 0.2sec; normal amplitude is 0.3mV.

102.

A  patient has  a  transversal laceration in the spinal cord. What respiratory changes will result from this?

Explanation

103.

In   a   healthy   adult   speed   of   the excitement conduction through the  atrioventricular node is 0,02-0,05 m/sec. Atrioventricular delay enables:

Explanation

The atrial conductive system is organized so that the cardiac impulse does not travel from the atria into the ventricles too rapidly; this delay allows time for the atria to fully contract and empty their blood into the ventricles before ventricular contraction begins. It is primarily the AV node and its adjacent conductive fibers that delay this transmission into the ventricles.

104.

Products of some  proteins hydrolysis and   modification    are   the   biologically active substances  called hormones. Lipotropin,    corticotropin,    melanotropin and endorphins are synthesized  in the hypophysis  of the following protein:

Explanation

When adrenocorticotropic hormone (ACTH) is secreted by the anterior pituitary gland, several other hormones that have similar chemical structures are secreted simultaneously. The reason for this is that the gene that is transcribed to form the RNA molecule that causes ACTH synthesis initially causes the formation of a considerably larger protein, a preprohormone called proopiomelanocortin (POMC), which is the precursor of ACTH (corticotrophin) and several other peptides, including melanocyte-stimulating hormone (melanotropin), β-lipotropin, β-endorphin and a few others.

105.

A middle-aged man went to a foreign country because he had been offered a job there.  However he had been unemployed for  quite   a  long  time.  What   endocrine glands were exhausted most of all in this man?

Explanation

Due to the fact that he has been unemployed for a long time, the man has been stressed. Unemployment can lead to psycho-emotional stress. The main stress organ in the body is the adrenal gland producing stress hormones (cortisol, catecholamines). Therefore, this gland must have been exhausted, if the man has stayed unemployed for a long time.

106.

Cooling of the human body in water is much  more  faster  than  in the  air.  What way  of  heat  emission  in  water  is much more effective?

Explanation

Conduction is a way the body eliminates heat by means of direct contact with another object. Heat is transferred down the temperature gradient (i.e. from the object of higher temperature to the object of lower temperature). Conduction requires contact with another object (Key words:  in water).

Heat Radiation is a way the surface of the human body emits heat to the environment in the form of infrared rays. The amount of heat the body radiates to the environment is proportional to the surface of radiation area and to the difference between the mean values of skin and environment temperature. The surface radiation area is the total surface area of body parts that contact the air. Elimination of heat by radiation increases with a decrease in ambient temperature and decreases with its increase. It is possible to reduce elimination of heat by radiation via reduction of the surface of radiation area (“winding oneself into a ball”). Heat radiation does not require a medium for transfer of heat. (Key words: naked or lightly clothed).

Convection is a way the body eliminates heat by means of transferring heat via moving particles of air or water. To dissipate heat by means of convection, body surface shall be airflowed at a temperature that is lower than the temperature of the skin. At that, air layer contacting with the skin warms up, decreases its density, rises and is replaced by cooler, denser air. By increasing the speed of the air flow (wind, ventilation) heat emission increases significantly as well (forced convection). Convection requires convection current; current of gases or liquids (Key words: air over exposed area of skin).

Evaporation is a way the body dissipates heat to the environment by its evaporation via sweat or evaporation of moisture from the skin and respiratory tract mucous membranes of (“wet” heat loss). Evaporation closely related to relative humidity.

107.

After  a surgery  a 36-year-old  woman was given an intravenous injection of concentrated albumin  solution.  This  has induced   intensified   water   movement  in the following direction:

Explanation

Albumin maintains the oncotic pressure in the blood vessels, it does not go out of the blood vessels. Injection of concentrated solution of albumin will increase the oncotic pressure in the blood vessel thereby causing water to move from the interstitial/intercellular space to the blood vessel (i.e. the capillaries).

    In contrast, glucose can pass through the capillaries into the interstitial/intercellular space but it does not readily enter the cell. Therefore, it increases the oncotic pressure in the interstitial space and cause water to move from the intracellular (inside the cell) space to the interstitial/intercellular space.

108.

Examination of  a  patient suffering from  chronic  hepatitis revealed  a significant decrease in the synthesis and secretion of bile acids. What process will be mainly disturbed in the patient’s bowels?

Explanation

The findings are specific for obstruction of bile duct and bile acid deficiency.

Findings:

* malabsorption: bile salts do not enter the Small Intestine; no emulsification of fat.

*light coloured stool: due to lack of urobilin (which leads to lack of stercobilin).

*Jaundice (posthepatic, mechanic, obstructive): increased conjugated Bilirubin.

* Steatorrhea

 

109.

While determining power inputs of a patient’s  organism  it was established that the   respiratory  coefficient   equaled  1,0. This  means  that  in the  cells of the  patient the following substances are mainly oxidized:

Explanation

Minute O2 uptake – 1000ml

    Minute CO2 emission – 1000ml

    Respiratory Quotient (RQ) = vCO2 /vO2 = 1000/1000(ml) = 1

   Carbohydrate = 1; Fat = 0.7; Protein = 0.8

110. During   an  experiment  the   dorsal roots of the spinal cord of an animal have been  cut. What  changes  will be observed in the innervation zone?

Explanation

FullSizeRender (16)

There are two types of roots of spinal nerves:

·        Anterior (ventral, motor) root: it arises from the anterolateral sulcus and contains a set of axons of motor neurons located within the anterior columns; the anterior roots number 31 pairs.

·        Posterior (dorsal, sensory) root: it is a set of central processes of sensory pseudounipolar neurons located within the spinal ganglia; the posterior roots also number 31 pairs. Cutting this root will lead to loss of sensory stimulus.

111. A  patient has  osmotic  pressure of blood plasma at the rate of 350 mOsmol/l (norm  is 300 mOsmol/l).  This will cause hypersecretion of the following hormone:

Explanation

     Antidiuretic hormone (vasopressin) is secreted in response to decrease blood volume and increase plasma osmolarity. It binds to receptors on principal cells of collecting ductules causing increase number of aquaporins and increase water reabsorption which leads to decreased diuresis.

↑oncotic (colloid-osmotic) pressure → ↑vasopressin → ↑H2O reabsorption → Normal osmotic pressure. ↑H2O reabsorption will balance the excess osmotic pressure.

↓vasopressin → ↓H2O reabsorption → polyuria

112.

During   an  experiment  vagus branches that  innervate heart  are  being stimulated. This  has  stopped conduction of excitement from the atria to the ventricles. The reason  for it are electrophysical changes in the following structures:

Explanation

Atrioventricular (AV) node serves as the gateway for conduction of impulses from the atria to the ventricle. Stimulation of the parasympathetic nerves to the heart (vagus nerve) causes the neurotransmitter acetylcholine to be released at the vagal endings. This neurotransmitter has two major effects on the heart. First, it decreases the rate of rhythm of the sinus node, and second, it decreases the excitability of the AV junctional fibers between the atrial musculature and the AV node, thereby slowing transmission of the cardiac impulse into the ventricles. In the AV node, a state of hyperpolarization caused by vagal stimulation makes it difficult for the small atrial fibers entering the node to generate enough electricity to excite the nodal fibers. A moderate decrease simply delays conduction of the impulse, but a large decrease blocks conduction entirely.

113. A man presents with increased  heart rate, mydriatic pupils, dry mouth. This condition results  from  the  activation   of the following system of function  regulation:

Explanation

Muscarinic receptors belong to the parasympathetic system. Muscarinic effects include miosis, spasm of accommodation, increasing of lacrimal, salivary, gastrointestinal, bronchial and sweat glands secretion, increase of smooth muscle tonus of internal organs, bradycardia, decreased arterial pressure.

image

Block of M-cholinoreceptor or activation sympathetic nervous system will produce the opposite effects as described in the question (mydriatic pupils - opposite to miosis; dry mouth - opposite to increase salivation)

114.

Vagus nerves of an experimental animal have been cut on the both sides. What respiratory changes will result from this?

Explanation

115. A  60-year-old   patient  presents with weakened peristaltic activity of the bowels. Which of the following foodstuffs would stimulate peristalsis most of all?

Explanation

The various cereals used for bread when coarsely ground contain a large proportion of the external envelope of the grains, which is more or less hard and rough; and by its presence in the intestine it stimulates peristalsis through mechanical irritation. For the above reasons, the following articles of diet tend to overcome constipation: coarse Graham bread, Rye bread, Oatmeal, Brown or “wholemeal” bread, Boston brown bread, shredded wheat.

116.

A  student takes  notes  of  a  lecture. Quality  of his notes  became  significantly worse when his neighbours began talking. What type of conditional reflex inhibition was the cause of it?

Explanation

The dog is conditioned to salivate at the sight of food and flash of light – that is a conditioned reflex that requires learning, memory and recall of previous experience (likewise the student, taking notes requires learning, memory and recall of previous experience). The established conditioned reflexes can be inhibited: externally and internally.

External inhibition: disturbing factors like a stranger, sudden noise (the students talking) or a strong smell can abolish the conditioned reflex and inhibit salivary secretion. This extra stimulus evokes the animal’s curiosity  and distracts the attention. Internal inhibition can be:

*Extinction of conditioned reflex: failure to reinforce the conditioned reflex by unconditioned stimulus.

*Differential: alteration of conditioned stimulus.

117. ECG  of a patient with hyperfunction of thyroid  gland showed  heart  hurry.  It is indicated by depression of the following ECG element:

Explanation

imagekrushkrok No28 (2009)                                                                FAST HEART BEAT  

Thyroid hormone increases synthesis of β-adrenergic receptors for catecholamines. Catecholamines (epinephrine) exert their effect on the heart by binding to β1-adrenoreceptors, which in turn increases the heart rate. Increase in heart rate shows a decrease in R-R interval on the ECG. This can lead to clinical manifestations such as systemic hypertension and high output heart failure.

118. As  a result  of destruction of certain brainstem structures an  animal  has  lost its  orientative  reflexes   in  response   to strong   photic   stimuli.   What   structures were destroyed?y

Explanation

     Quadritubercular bodies/tectal plate is the dorsal portion of the midbrain comprises 4 colliculi – two superior and two inferior. The nuclei of colliculi are responsible for reflexes associated with sudden sound and visual stimuli (auditory and visual orientative reflexes); they also maintain consciousness. The nuclei give rise to the tectospinal tract. Superior or Anterior colliculi – visual orientative reflex; Inferior or Posterior colliculi – auditory orientative reflex.

119. A patient with disturbed cerebral circulation   has  problems with  deglutition. What part of brain was damaged?

Explanation

Brainstem is the part of the brain formed by medulla oblongata, pons and midbrain. It contains many centers for regulation of vital functions in the body. Medulla oblongata has many important centers which control vital functions like the respiratory centers; vasomotor center; deglutition center; vomiting center; superior and inferior salivatory nuclei; cranial nerve nuclei; vestibular nuclei. Deglutition center regulates the pharyngeal and esophageal stages of deglutition. Disturbed cerebral circulation can disrupt proper functioning of these centers.
120. Golgi  complex   exports   substances from    a   cell   due    to    the    fusion    of the membrane saccule with the cell membrane.  The   saccule   contents  flows out. What process is it?

Explanation

image Exocytosis is the process by which a vesicle moves from the cytoplasm to the plasma membrane, where it discharges its contents to the extracellular space. A variety of molecules produced by the cell for export are initially delivered from the site of their formation to the golgi apparatus. The next step involves sorting and packaging the secretory product into transport vesicles that are destined to fuse with the plasma membrane in a process known as exocytosis.
121.

Rest  potential of a cell equals  80 mV . At what stage of action potential did the membrane potential equal +30 mV ?

Explanation

At rest, the axon membrane is slightly polarized to about -70mV (or -80mV), meaning the intracellular fluid (ICF) is relatively negative to the extracellular fluid (ECF). An action potential occurs when a portion of the membrane rapidly depolarizes and then repolarizes again to the original resting state. The process is initiated by a threshold level stimulus, such as a nearby change in membrane potential (threshold potential, local potential). At threshold (about -55mV), many Na+ voltage-gated channels open. Na+ ions entering the cell make the membrane potential less negative. More Na+ channels open as a result and a cycle of depolarization develops. When the membrane potential reaches about +30mV (reverse polarization), the timed Na+ channels close due to inactivation and the Na+ influx stops. K+ voltage-gated channels open as Na+ channels close, in a delayed response to the original stimulus.

122. A  35  year  old  man  got  an  injury that  caused  complete disruption of  spinal  cord  at  the  level of the  first cervical segment.   What  respiration changes  will be observed?

Explanation

123. In  course  of an  experiment a peripheral section of vagus of an expiremental animal is being stimulated. What changes will be observed?

Explanation

Vagus nerve gives parasympathetic innervations to the heart. The vagal fibers are distributed mainly to the atria and not much to the ventricles, where the power contraction of the heart occurs. This explains the effect of vagal stimulation mainly to decrease heart rate rather than to decrease greatly the strength of heart contraction.

124. A patient complains  of dizziness and hearing loss. What nerve is damaged?

Explanation

imageimage  The receptor areas of the vestibular labyrinth are represented with the following structures:

·        Macula of Utricle

·        Macula of Saccule

·        Ampullary crests

The first two detect linear motion, while the ampullary crest detect angular motion. The vestibulocochlear nerve supply these receptors. Both maculae consist of the sensory hair cells covered with jelly-like susbstance. The substance contains the crystals of calcium carbonate called otoliths (vestibular otolith). The utricle and saccule detect linear movement, also contributing to balance. The ampullary crests reside within each membranous ampulla. They also comprise the sensory hair cells covered with the same jelly-like substance called the ampullary cupula. The ampullae is the sensory organ in the semicircular canal that sense angular (rotational) acceleration of the head, thereby regulating balance. If vestibulocochlear nerve (CN VIII) supply the receptors, then damage to this nerve can cause hearing loss.
125. In course of an experiment a skeletal muscle is being stimulated by a series of electric impulses. What type of muscle contraction will arise, if every subsequent impulse comes in the period of relaxation of single muscle contraction?

Explanation

krushkrok No21 (2010)

Tetanus is defined as the sustained contraction of muscle due to repeated stimuli with high frequency. When the multiple stimuli are applied at a higher frequency in such a way that the successive stimuli fall during contraction period (period of shortening) of previous twitch, the muscle remains in state of tetanus. While increasing the frequency, fusion of contractions increases every time and finally complete tetanus occurs. Holotetanus – complete tetanus.

When the frequency of stimuli is not sufficient to cause tetanus, the fusion of contractions is not complete and then we have – incomplete/partial/waved tetanus. This occurs (i.e. the next stimuli occurs) during the period  of relaxation.