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أسئلة فسيولوجي CVS - بنك أسئلة Cardiovascular system MCQ

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أسئلة فسيولوجي CVS - بنك أسئلة Cardiovascular system MCQ

Cardiovascular system MCQ’s

1- Which of these statements is false:-
a- most of total blood volume is contained in veins
b- Capillaries have a greater total surface area than any other vessels
c- Exchange between blood and tissue fluid occur across the wall of venules
d- Small arteries and arterioles present great resistance to blood flow
Answer: C

2- All arteries in the body contain oxygen-rich blood with exception of:
a- The aorta
b- The pulmonary artery
c- The renal artery
d- The coronary arteries
Answer: B

3- The first heart sound is produce by closing of:
a-aortic semilunar valve
b- pulmonary semilunar valve
c- tricuspid valve
d- Bicuspid valve
e- Both AV valves
Answer: E

4- The first heart sound is produced at:
a- The beginning of systole
b- The end of systole
c- The beginning of diastole
d- The end of diastole
Answer: A

5- The QRS wave of ECG is produced by:
a-Depolarization of atria
b- Repolarization of atria
c- Depolarization of ventricles
d- Repolarization of ventricles
Answer: C

6- The second heart sound immediately follows the occurance of:
a- P wave b- QRS wave
c- T wave
Answer: C

7- The cell that normally have the fastest rate of spontaneous diastolic depolarization
are located in:
a- SA node b- AV node
c- Bundle of His d- Purkinje fibers
Answer: A

8- Loss of the elasticity of the arterial wall:
a- Rises the diastolic arterial pressure
b- Increases the peripheral resistance
c- Rises the systolic arterial pressure
d- Decreases the velocity of arterial pulse wave
Answer: C

9- The increasing in the blood flow to a rhythmically excersing muscle depend on:
a- Release of sympathetic vasoconstrictor
b- Active dilation of capillaries
c- Vasoconstriction in vascular bed adjacent to excersing muscle
d- Metabolites produced in the excersing muscle
Answer: D, the cause during exercise the active muscles have hypoxia so, release metabolites as vasodilators which do vasodilation on vessels of active muscle as
adenosine

10- The end-diastolic volume of left ventricle :
a- Is reduced in the aortic valve stenosis
b- Is reduced in the mitral valve stenosis
c- Is reduced during inspiration
d- depends entirely on the contraction of the left atria
Answer: C

11- A ventricular extrasystole:
a- Is associated with normal QRS
b- Tend to be followed by by compensatory period
c- Caused by increase SAN activity
d- Always produces a pulse at the wrist
Answer: B

12- Hypertension is may be caused by:
a- Hypoxia due to chronic respiratory failure
b- Hypertrophy of left ventricle
c- Excessive secretion of aldosterone
d- Excessive muscle exercise
Answer: C

13- Starling law of heart:
a- Dose not operate in failing heart
b- Explain the increase in HR produced by exercise
c- Explain the increase in CO that occurs when venous return is increased
d- Explain the increase in CO when sympathetic cardiac nerves are stimulated
Answer: C

14- In second degree heart block:
a-The ventricular rate is slower than the atrial rate
b- The ventricular electrocardiographic complexes are distorted
c- Stroke volume is decreased at rest
d- Cardiac output in increased at rest
Answer: B

15- Ventricular filling:
a- Is reduced of aortic valve is stenosis
b- Depends entirely on contraction of atria
c- Is reduced if the mitral valve is stenosis
d- Gives rise to second heart sound
Answer: C

16- The greatest amount of ventricular filling occurs during:
a- The first one third of diastole
b- The middle one third of diastole
c- The last one third of diastole
d- The ventricular systole
Answer: A


17- Second degree of heart block:
a- Is caused by wandering atrial pacemaker
b- Usually involve retrograde conduction to atria
c- Always involve a lost ventricular depolarization every so many P waves
d- Most of QRS complexes are wide and bizarre
Answer: C


18- Stimulation of cardiac adrenergic sympathetic neurons:
a- Increase P-R interval of ECG
b- Decrease the delay at the AV node
c- Decrease the stroke work of ventricles
d- Increase the end-systolic volume of ventricles
Answer: B


19- Which of the following is the most common cause of an increase
Coronary blood flow:
a- Decreased coronary perfusion pressure
b- Increased diastolic ventricular pressure
c- Increased stimulation of alpha adrenergic receptors in the heart
d- Increased stimulation of beta adrenergic receptors in the heart
Answer: C


20- Cardiac output:
a- Is usually expressed as the combined output of left and right ventricles per minute
b- Increases mainly when the heart rate is very high
c- Rises when the subject changes from standing to lying down position
d- Is reduced reflexly in a hot environment
Answer: C


21- in atrial fibrillation :
a- sinus arrhythmia commonly occurs.
b- the ventricular rate is usualy determined by a ventricular pace maker.
c- P wave usually absent from the ECG.
d- the ECG show no evidence electrical activity in the atria .
Answer: C , in atrial fibrillation there is no P wave and are replaced by fine oscillations called F waves and the QRS and T waves are normal in shape but irregular in rate.


22- During cardiac cycle :-
a-myocardial contraction begin in left atrium .
b- myocardial contraction begin in right atrium .
c- the atria contract when the mitral and tricuspid valves are closed.
d- excitation of epicardial myocardium precedes excitation of endocardium.
Answer : B, the SA node which generate impulse spontaneously is located in the right
atrium then conduct impulses to the left atrium by intrenodal system ((ant. mid. and
post. internodal tracts)).


23- During the transmission of action potential through conducting system of the
heart ,there is a temporary delay at :-
a- AV-bundle . b- SA node
c- purkinje fibers. d- AV node.
Answer : D, there is a delay in AV node by 0.1 second , that due to 2 factors 1- nodal
muscle fibers are small in size and poor in gap junctions , so they are slowly -
conducting 2- th special characteristic of N region of AV node.
24- increased venous return resualt in :-
a- increased end systolic volume. b- increased end diastolic volume.
c- increased atrial pressure. d- increased peripheral resistance .
Answer : B, increase venous return lead to increase atria pressure which leads to
increase end diastolic volume .
decrease venous return lead to decrease atrial pressure which leads to decrease end
diastolic volume.

25- because of the baroreceptors reflex, whan normal arterial pressure decrease, the:
a- heart rate decreases. b- stroke volume decreases .
c- frequency of afferent action potential from baroreceptors decrease .
d- cardioregulatory center stimulate parasympathetic nervous system.
Answer : C, baroreceptors are located in aortic arch and carotid sinus and they oppose
the changes in the arterial blood pressure by the reflexes eg:- when the ABP decrease
the discharge rate from baroreceptors will decrease lead to decrease the activity of CIC
and VDC.

26- the resistance to blood flow is greatest in the :-
a-aorta b- arterioles. c- capillaries. d- venules.
Answer : B, arterioles are muscular high resistance vessels which regulate blood flow to
tissue and maintain ABP.

27- both ADH and aldosterone act to :-
a- Increase urine Volume. b- increase blood volume.
c- Increase tottal peripheral resistance. d- produce all of these effects.
Answer : B, ADH increase water reabsorbtion which lead to increase blood volume.
Aldosterone increase Na and water reabsorbtion which lead to increase blood volume.

28- the sound of korotkoff are produced by :-
a- closing of semilunar valves. b- closing of AV valves.
c- the turbulent flow of blood through an artery. d- elastic recoil of aorta .
Answer : C, the turbulent flow of blood through an artery produce korotkoff sound .

29- an increase in blood volume will cause :-
a- a decrease in ADH secretion. b- an increase in Na excretion in the
urine .
c- a decrease in renin secretion. d- all of these .
Answer : D, increase in blood volume cause all of the above effects.

30- during the phase of the isovolumetric relaxation of the ventricles,the pressure on
the ventricles is:-
a- rising. b- falling. c- first rising, then falling. d-constant.

Answer : B, the ventricular pressure is rising in isometric contraction phase, maximum
ejection phase and start to decrease in reduced ejection phase and isometric relaxation
phase then start to increase in maximum filling phase and reduced filling phase.

31- according to Frank-Starling law of the heart , the strength of ventricular
contraction :-
a- directly proportional to the end-diastolic volume.
b- inversely proportional the end-diastolic volume.
c- independent of end diastolic volume.
Answer : A, Frank-Starling law "with in limits ,the force of myocardial contraction is
directly proportional to the initial length of cardiac muscle fibers ".

32- edema is caused by :-
a- high blood pressure.
b- Decrease plasma protein concentration.
c- leakage of the plasma proteins into interstitial fluid.
d- blockage of lymphatic vessels.
e- all of the above.
Answer :E, edema is caused by increase in hydrostatic pressure by increase blood
pressure and decrease in osmotic pressure by decrease in plasma proteins
concentration also caused by in adequate lymph drinage.

33- the volume of blood pumped per minute by the left ventricle is :-
a- greater than the volume pumped by the right ventricle.
b- less than the volume pumped by the right ventricle.
c- the same as the volume pumped by the right ventricle.
d- either less or greater than the volume pumped by the right ventricle depending on
the strength of the contraction.
Answer is : C, CO= the volume of blood pumped from each ventricle per minute so
cardiac output of Right ventricle = Left ventricle .

34- blood pressure is lowest in :-
a- arteries. b- arterioles. c- capillaries.
d- venules. e- veins.
Answer : E, blood pressure is high in arteries and low in veins .

35- stretch receptors in the aortic arch and the carotid sinus :-
a- stimulate secretion of atrial natriuretic peptide.
b- serve as a baroreceptors that affect activity of vagus and sympathetic nerve.
c- serve as osmoreceptoes that stimulate the release of ADH .
d- stimulate renin secretion, thus increasing angiotensinogen Il formation.
Answer : B, aortic arch and carotid sinus are arterial baroreceptors witch maintain the
arterial bloodpressure by provid the nervous system with information about the level of
ABP by the effect the activity of vagus and sympathetic nerves.


36- Angiotensinogen ll :-
a- stimulate vasoconstriction b- stimulate the Adrenal cortex to secret
aldosterone.
c- inhibit the action of bradykinine. d- all of the above.
Answer : D, angiotensinogen ll produced in the lungs by the action of angiotensinogen
converting enzyme ACE on the angiotensinogen l which increases the ABP by all of the
previous actions .
37- the pulse pressure is measure of :-
a- the number of heart beat per minute. b- the sum of diastolic and systolic
pressures.
c- the difference between the systolic and diastolic pressures .
d-the difference between the arterial and venous pressures .
Answer : C, pulse pressure =systolic pressure (120) - diastolic pressure (80) = 40.
38- which part of ECG corresponds to ventricular repolarization :-
a- the P wave. b- the QRS complex. c- the T wave. d- the U wave .
e- the P-R interval.
Answer : C .
39 - Which of the following normally has a slowly depolarizing “pre-potential”:
a - sinoatrial node b - atrial muscles cells c - bundle of his
d - purkinje fibers e - ventricular muscle cells
Answer: A, the fast response “depolarization” occur in ventricle, His-purkinje system and
Atria ‘coz they are rich in gap junction. The slow response “depolarization” occur in S-A
node and A-V node ‘coz they are small in size and poor in gap junction.


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40 - Currents are caused by opening of which of the following channels contribute to
the repolarization phase of the action potential of the ventricular muscles fibers:
a - Na channels b - Cl channels c - Ca2 channels
d - K channels e - HCO3 channels
Answer: D, the action potential of ventricular muscles fibers is fast response, the
depolarization phase is caused by Na influx. The pleatve is caused by Ca2 influx and K
efflux, and the repolarization phase is caused by K efflux.
41 - In second degree of the heart block:
a - the ventricular rate is lower than atrial
b - the ventricular ECG complex are distorted
c - there is a high incidence of ventricular
d - stroke volume “SV” is decreased
e - cardiac output “CO” is increased
42 - The forth heart sound is caused by:
a - closure of aortic and pulmonary
b - vibrations in the ventricular wall during systole
c - ventricular filling
d - closure of mitral and tricuspid valves
e - retrograde flow in the vena cave
Answer: C, 1st sound → produced by closure of AV valves


2
nd sound → produced by closure of semilunar valves
3
rd sound → produced by oscillation of rushing blood from atria into ventricles
4
th sound → produced by ventricular filling.


43 - The dicrotic notch on the aortic presser curve is caused by:
a - closure of mitral valve
b - closure of tricuspid valve
c - closure of aortic valve
d - closure of pulmonary valve
e - rapid filling of left ventricle
Answer: C, the dicrotic notch is caused by small oscillation on the downslope of aortic
valve, and is followed by dicrotic wave.
44 - The work performed by the left ventricle, ‘coz in the left ventricle:
a - the contraction is slower
b - the wall is thicker


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c - the stroke volume is greater
d - the preload is greater
e - the after-load is greater
45 - Which of the following has the highest total cross-section area in the body:
a - arteries b - arterioles c - capillaries
d - venules e – veins
Answer: C
46 - The pressure in capillary in skeletal muscle is 35 mmHg at the arteriolar end and
14 mmHg at the venular end, while the interstitial presser is zero mmHg. The colloid
osmotic pressure is 25 mmHg in capillary and 1 mmHg in the interstitium. The net
force producing fluid movement across the capillary wall at its arteriolar end is:
a - 3 mmHg out of the capillary
b - 3 mmHg into the capillary
c - 10 mmHg out of the capillary
d - 11 mmHg out of the capillary
e - 11 mmHg into the capillary
Answer: D, The net force = pressure favor filtration - pressure favor reabsorption


= ( 35 + 1 ) - ( 0 + 25) = 36 - 25 = 11


the pressure favor filtration more than reabsorption so will be out of the capillary
47 - Which of these organ is able to tolerate the greatest reduction in blood flow:
a - brain b - heart c - skeletal muscles d - skin
Answer: D, 1st organ sensitive to hypoxia “Brain”


2
nd organ sensitive to hypoxia “Heart”
3
rd organ sensitive to hypoxia “Kidney”


48 - Which of these is a paracrine regulator that stimulates vasoconstriction:
a - nitric oxide “NO” b - prostacyclin
c - bradykinin e - endothelin-1
Answer: D, some vasodilator metabolites bradykinin, nitric oxide, adenosine, prostacyclin
and others. Some vasoconstrictor substances as; prostaglandin, histamine, serotonin and
endothein-1.
49 - An ischemic injury to the heart that destroys myocardial cells is:
a - angina pectoris b - a myocardial infarction


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c - fibrillation d - heart block
Answer: B
50 - The windkessel effect has the greatest influence on magnitude of the pulse
presser in thee:
a - Aorta b - capillary c - venules d - veins
Answer: A
51 - Neck vein pulsation due to:
a - atrial systole b - atrial diastole
c - peripheral resistance “PR” d - none of the above
52 - When moving from supine to erect position:
a - mean arterial presser increase
b - skin perfusion immediately decrease
c - cardiac output increase
d - TPR increase
53 - The slowest conduction occurs in:
a - atrium b - AV node
c - bundle of His d - purkinje fibers
Answer: B
54 - Baroreceptors are located in all; Except:
a - Aortic sinus b - Aortic bodies
c - Carotid sinus d - Aortic arch
55 - sympathetic stimulation of the heart will increase:
a - cardiac output
b - coronary blood flow
c - all of the above
56 - All are function of the CVS; Except:
a - linked to other system
b - nutrients absorption
c - involved in gas exchange
d - its whole blood easy going to flow
57 - Arteries differ from veins by:


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a - moving toward the heart
b - have strong vasoconstriction
c - where gas exchange takes place
d - have elastic fiber and circular smooth muscle
58- Causes of edema all, except
a. Increase blood hydrostatic pressure
b. Decrease blood osmotic pressure
c. Leaking cap wall
d. Decrease interstitial and lymphatic pressure
Answer D; see causes of edema on Magdi Sabry, page 123.


59- Vasodilation of arteriole peripherally by
a. Decrease tissue activity
b. Decrease CO2
c. Decrease lactic acid
d. Decrease O2
Answer D; Vasodilation of arterioles occur in hypoxia, increased metabolic activity and
whenever releasing vasodilator metabolites as adenosine, lactic acid, K and others.
60- At rest the source of energy for cardiac muscle
a. Glycogen
b. CHO
c. Fat
d. B.C
Answer C; heart mainly FA 60%, glucose 20% and lactate 20% as a source of energy
during rest, but during exercise it uses lactate as source of energy.
61- All happened during muscle exercise except
a. Increase heart rate
b. Increase stroke volume
c. Increase venous return
d. Decrease blood flow to active mechanism
Answer D; see effects of exercise on circulation, page 141.


62- Which is false about neural regulation of ABP
a. Center located in pons
b. VMC or presser area
c. CIC or depressor area
d. Autonomic nerve fibers
Answer A; cardiovascular center is located in medulla oblongata and include CIC
‘’depressor” its stimulation lead to bradycardia, VMC “presser” its stimulation lead to
vasoconstriction or vasodilation.
63- Factor affect B.P more than other
a. F > M
b. Children > elderly
c. Sleep > exercise
d. Pregnancy and hyperthyroidism
Answer D; BP is increase in pregnancy due to increase cardiac output due to increase
uterine blood flow and increase in hyperthyroidism due to increase cardiac output and
systolic blood pressure.


64- The shifting upward and to the left of frank-sterling law or ventricular function
curve may result from
a. Decrease heart rate
b. Increase intropicity and catechol amines
c. Increased venous return to heart
d. Heart failure
Answer B; this curve showing the relation between EDV and ventricular performance
and if it shifting upward and to left, it shows the effect of positive inotropic factors.
If it shifting downward and to the right, it shows the effect of negative inotropic factors


65- The Sino-atrial node
a. But not atrio-ventricular node receives parasympathetic nerve supply
b. Is connected by thin band of porkinje tissue with A.V node
c. Pacemaker cells undergo a faster rate of diastolic depolarization at 39 C then at
37C
d. Pacemaker cells undergo a faster rate of diastolic depolarization in the presence
of acetylcholine


66- When the radius of the resistance vessels is increased which of the following is
increased, which of the following is increased
a. Systolic blood pressure
b. Diastolic blood pressure
c. Viscosity of blood
d. Hematocrit
e. Capillary blood flow
Answer E; R= 8Ln/ t r4
R; resistance L; length of vessels n; blood viscosity t; 3.14 r; radius
↑radius→↓PR→↓BP
67- Which of the following dose not dilate arterioles in skin
a. Increased body temperature
b. Epinephrine
c. Brady kinine
d. Substance p
e. Vasopressin
Answer E
68- All the following increase excitability except
a. ↓Ca
b. ↓O2
c. ↑Temperature
d. Thyroxin
Answer B; excitability is increased in hypocalcaemia in moderate increase body
temperature.
69- Decrease in blood pressure lead to
a. ↑Renin
b. ↓Aldosterone
c. ↓Angiotensin
Answer A; as ↓BP→ ↑Renin→ ↑Aldosterone→ ↑Na and water retention→↑BP

↑ angiotensin→ V.C→ ↑ BP
70- Decrease elasticity of aorta lead to
a. Increase PR


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b. Decrease blood viscosity
c. Increase systolic pressure
d. Increase diastolic pressure
71- Sino atrial node cells are
a. Found on both atria
b. Innervated by somatic nerve
c. Unable to generate impulses when completely innervated
d. Innervated by vagus nerve
Answer D; Sino atrial node is the pacemaker of the heart, which is located in the right
atrium and it, generate impulses spontaneously and innervated by both sympathetic
and parasympathetic system.
72- The strength of left ventricle contraction increase when
a. Increased end diastolic volume
b. Hyperkalemia
c. Hypocalcaemia
d. Strenuous exercise has no effect
73- Which stimulate chemoreceptor
a. Hemorrhage
b. Circulator shock
c. Hypoxia
d. All of the above
Answer D; chemoreceptor reflexes are stimulated when ABP below 60mmHg and on
hypoxia mainly the peripheral chemoreceptor. The center chemoreceptor is stimulated
by hypercapnia
74- Effect of sympathetic stimulation on pacemaker potential
a. To be faster
b. To be slower
c. Decrease heart rate
d. B and c
Answer A; sympathetic stimulation lead to increase all properties of heart.
75- Sympathetic drive to the heart will increase
a. Blood flow to coronary arteries
b. Purkinje fibers conduction


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c. Ejection fraction of left ventricle
d. All of the above
Answer d; sympathetic stimulation of the heart lead to increase all properties of the
heart by stimulation the pacemaker.
76- Cardiac output
a. Expressed as the product of one ventricle in L/min
b. Increased when heart rate increase in all situations
c. Dose not increase in exercise following denervation of heart
d. Decrease when laying down
Answer C; may be due to absence the sympathetic activity.
77- In denervated heart, lift ventricular stroke work increase when
a. Increase blood volume
b. Increase venous return
c. Increase end diastolic volume
d. All of the above
Answer D; increase blood volume lead to increase venous return so increased EDV so
increased stroke volume.
87-The nerve supply to the heart as follow
a. SA node is innervated by sympathetic only
b. Atrial is innervated by both sympathetic and barasympathetic
c. Rt vagus supply SA node and A.V node
d. Lift vagus supply SA node
e. Parasympathetic supply ventricular muscle
79- The heart rate is increased by all the following except
a. Fever
b. Increased venous return
c. Atropine
d. Hypothyroidism
e. Adrenaline
Answer D ; Fever, Atropine, Adrenaline, venous return and thyroxin increase heart rate
so Hypothyroidism decrease heart rate.


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80-Stroke volume
a. Increase as a result of increased after load
b. Equal end diastolic volume minus end systolic volume
c. Increases as heart rate increased by electrical pacing
d. Increased by parasympathetic stimulation
e. Increased by Ca channel blocks
Answer B; stroke volume is the volume of the blood that pumped at each ventricle per
beat and it is equal the difference between EDV and ESV.
81- The chemoreceptor are found in
a. The lung
b. Glomus body
c. Aortic arch
d. Carotid sinus
e. Medulla
Answer E; the center chemoreceptor are located in medulla and the peripheral
chemoreceptor are located in aortic and carotid bodies.


82-The vessel responsible for regulation of blood pressure
a. Medium size arteries
b. Small veins
c. Capillaries
d. Venoles
e. Arterioles
Answer C; as the answer of Q26


83- Which of the following substances will be most likely to dilate systemic arterioles
a. Endothelin
b. ADH
c. Histamine
d. Noradrenaline
e. Aldosterone


84-In the heart, within physiological limits the force of contraction is directly
proportional to
a. Pacemaker activity
b. AV node delay
c. Initial length of cardiac muscle
d. Respiratory rate
e. Vagal stimulation


85- The volume of blood is greatest in
a. Systemic capillaries
b. Veins
c. Arteries
d. The spleen
e. The heart
Answer B; blood volume in systemic veins 54%, in heart 12% in arterial system 11% in
capillaries 5% and in pulmonary vessels 18%.
86-Cardiac output divided by heart rate equals to
a. Cardiac index
b. Cardiac efficiency
c. Mean arterial pressure
d. Stroke volume
Answer D; CO= SV*HR ...... so CO/HR= SV
87-At rest the lift ventricular end systolic volume is
a. 10ml
b. 30ml
c. 50ml
d. 120ml
Answer C; EDV= 130ml........ESV=50ml......SV(stroke volume)= EDV-ESV= 130-50=80ml
88-Cardiac muscle has a long refractory period because
a. The impulse take about 0.2 s to travel from SA to AV node
b. It obeys to all-or-none law
c. Of the delay in Na influx
d. Of Ca influx
Answer D; the refractory period of cardiac muscle is longer than that of skeletal
muscle due to presence of plateau, which is due to Ca influx



CARDIOVASCULAR SYSTEM


1. Which of the following is part of the reflex response to an increase in arterial
pressure?
a) Decreased firing of carotid sinus baroreceptors
b) Increased sympathetic activity to the ventricles
c) Increased parasympathetic activity to the SA Node
d) Increased parasympathetic activity to the arterioles of skeletal muscles &
skin
e) Increased parasympathetic stimulation to the ventricles


2. Correct sequences of steps in short-term compensation for hemorrhage
include:
a) Decreased arterial pressure  Increased baroreceptor firing rate
b) Increased formation of Angiotensin II  Increased renin released by
kidneys
c) Decreased excretion of Na+and water  Increased aldosterone formation
d) Decreased firing of baroreceptors  Increased sympathetic activity
e) Decreased atrial volume  Increased volume receptor firing rate


3. Venous Return:
a) Is increased on standing
b) Decreases by deep inspiration
c) Is decreased by venoconstriction
d) When increased, activates Bainbridge reflex
e) When increased, increases end-systolic volume


4. The nerve supply to the heart is as follows:
a) SA Node is innervated by sympathetic only
b) Atrial muscle is innervated by both sympathetic & parasympathetic
c) Right vagus supplies SA node & AV node
d) Left vagus supplies SA node
e) Parasympathetic supplies ventricular muscle
5. Which of the following is not a characteristic of cardiac muscle?
a) It's a syncytium of muscle fibers
b) There are intercalated discs
c) Gap junctions cause spread of depolarization
d) Has myosin and actin muscles
e) There are paracellular spaces
6. The pacemaker prepotential:
a) Is due to a slow decrease in K+ influx
b) Is a slow increase in Resting Membrane Potential
c) Maintained by opening of long acting Ca2+ channels
d) Is augmented by opening of transient Ca2+ channels
e) Occurs only in the SA node


7. Parasympathetic stimulation results in:
a) Decreases K+ efflux in cardiac muscle
b) Increases Ca2+ influx in SA node
c) Bradycardia
d) Increases Na+ influx
e) Increasing slope of prepotential
8. Which of the following is true of the electrical activity of cardiac muscle?
a) Increased extracellular K+ causes depolarization
b) Repolarization is due to Na+ current
c) Extracellular Na+ affects the pacemaker potential
d) Plateu of action potential is due to Ca2+ influx
e) Initial repolarization is due to delayed K+ efflux
9. The conductive system of the heart does not include:
a) Internodal pathways
b) Bundle of His & its branches
c) Purkinje system of fibers
d) Interventricular septum
e) AV node
10. Which of the following is not true of the ECG?
a) Needs six pairs of electrodes
b) Is useful in detection of arrhythmias
c) It is recorded from limb leads


d) Its amplitude indicates the mass of cardiac muscle
e) The PR interval indicates strength of contraction
11. In a normal ECG:
a) The P wave indicates the condition of the conductive system
b) The P wave represents depolarization of atrial myocardium
c) QRS complex is mainly negative due to spread of depolarization down
d) QRS is due to depolarization in the ventricular septum
e) The T wave is a positive wave in all chest leads
12. Which of the following is true of the cardiac cycle?
a) Ventricular diastole follows atrial systole
b) Ventricular systole causes an immediate rise in aortic pressure
c) The beginning of systole causes closure of AV valves
d) Closure of semi-lunar valves gives rise to first heart sound
e) Isovolumetric relaxation occurs at the end of diastole
13. In the atrial pressure wave:
a) The maximum pressure is about 12 mmHg
b) Pressure remains constant while AV valves are closed
c) The C wave is due to bulging of AV valve during ventricular filling
d) The V wave is due to filling of the ventricles
e) The A wave is due to atrial systole


14. Protodiastole:
a) Is characterized by a rapid rise in aortic pressure
b) Occurs at the onset of diastole
c) Is a period in the cardiac cycle with constant blood pressure
d) Is the last one-third of diastole
e) Is a period of slow ejection from the ventricles
15. Which of the following statements is true of the heart sounds?
a) The first sound is of high pitch
b) The first sound is of longer duration than the second
c) They are produced by abnormal valves
d) The second sound is heard best at the apex
e) The second sound is due to the closure of AV valves
16. Pressure in the pulmonary artery is:
a) Higher than that in the right atrium
b) About 25 mmHg during systole
c) About 80 mmHg during diastole
d) Is lower than that in the right ventricle
e) Is regulated by parasympathetic innervation
17. The following is not correct about baroreceptors:
a) Found in the wall of carotid sinuses
b) Found in the aortic arch


c) Monitor pressure in the arterial system


d) Send impulses through the glosso-pharyngeal nerve
e) Normally fires during late systole
18. Chemoreceptors are:
a) Found in aortic and carotid sinuses
b) Stimulated best by hypercapnoea


c) Send impulses to vasomotor center through vagus nerve


d) Have a high blood flow rate
e) Are not sensitive to hydrogen ion concentration
19. At rest the LV end-systolic volume is:
a) 10 mL
b) 30 mL
c) 50 mL
d) 120 mL
e) 140 mL
20. The best site to measure mixed venous PO2 is:
a) Superior Vena Cava
b) Right Atrium
c) Pulmonary Artery
d) Pulmonary Vein
e) Left Ventricle


21. The atrial contraction component of ventricular filling is:
a) 5%
b) 10%
c) 30%
d) 50%
e) 80%
22. The lowest intrinsic discharge activity resides in the:
a) SA Node
b) AV Node
c) Bundle of His
d) Bundle of branches
e) Purkinje fibers
23. The highest oxygen extraction is found in the:
a) Resting skeletal muscles
b) Heart
c) Kidney
d) Brain
e) Skin
24. With a mixed venous oxygen content of 110 ml/L and an arterial oxygen
content of 150 ml/L an oxygen uptake of 280 ml/min, the cardiac output is:
a) 5 liters/ min
b) 6 liters/ min
c) 7 liters/ min
d) 8 liters/ min
e) 9 liters/ min
25. The pulmonary valve closes when the pressure in the right ventricle is about:
a) 0 mmHg
b) 15 mmHg
c) 30 mmHg
d) 50 mmHg
e) 120 mmHg
26. The velocity of blood flow is the slowest in:
a) Capillaries
b) Pulmonary vein
c) Small arteries
d) Inferior Vena Cava
e) Arterioles
27. The volume of blood is greatest in:
a) Systemic capillaries
b) Veins
c) Arteries
d) The spleen
e) The heart


28. Which of the following results in increased stroke volume?
a) An increase in end-diastolic volume
b) An increased after-load
c) Parasympathetic stimulation
d) An increase in the heart rate
e) Venodilation
29. During the cardiac cycle, closure of the aortic valve occurs at:
a) The end of isovolumetric contraction
b) The beginning of rapid ejection phase
c) The beginning of isometric relaxation
d) The end of systole
e) The end of rapid filling phase
30. SA node is the pacemaker of the heart because:
a) Location in the right atrium
b) Neural control
c) Natural leakiness to Cl-
d) Natural leakiness to K+
e) Fastest rate of discharge
31. Stroke Volume:
a) Is the volume of blood pumped by the heart per minute
b) Decreases by increased end-diastolic volume
c) Is decreased by increased afterload
d) From the left ventricle is more than from the right ventricle
e) Multiplied by heart rate gives cardiac index
32. In the ECG, the T wave denotes:
a) Atrial contraction
b) Atrial depolarization
c) Ventricular repolarization
d) SA node depolarization
e) Ventricular contraction
33. Cardiac Output (in liters per minute) divided by the heart rate (in beats per
minute) equals to:
a) Cardiac Index
b) Cardiac Efficiency
c) Mean Arterial Pressure
d) Stroke Volume
e) Blood Velocity
34. The segment of the vascular bed responsible for local regulation of blood flow
in most tissues is:
a) Distributing arteries
b) Large veins
c) Capillaries
d) Venules
e) Arterioles


35. Absolute refractory period of the heart:
a) Corresponds to the duration of relaxation
b) Lasts till half of cardiac contraction


c) Shorter than refractory period in skeletal muscle


d) Lasts till cardiac contraction
e) The heart can be stimulated by very strong stimulus
36. First heart sound occurs at the beginning of:
a) Isometric relaxation
b) Isotonic relaxation
c) Isovolumetric contraction
d) Isovolumetric relaxation
e) Atrial contraction
37. In the heart, within physiological limits the force of contraction is directly
proportional to the:
a) Pacemaker activity
b) AV nodal delay


c) Initial length of cardiac muscle


d) Respiratory rate
e) Vagal stimulation
38. Cardiac muscle has a long refractory period because:
a) The impulse takes about 0.2 s to travel from SA to AV node
b) It obeys the all-or-none law
c) Of the delay in Na+ influx


d) Of Ca2+ influx
e) Is more permeable to K+
39. Stimulation of baroreceptors leads to:
a) Tachycardia
b) Increased stroke volume
c) Stimulation of vasomotor center


d) Vasoconstriction
e) Decreased arterial blood pressure
40. The fourth heart sound is due to:
a) Closure of mitral and tricuspid valve
b) Iso-volumetric contraction
c) Iso-volumetric relaxation
d) Ventricular filling
e) Atrial systole


41. Frank Straling's law of the heart:
a) Explains the tachycardia caused by increased venouse return
b) Explains the tachycardia of exercise
c) Does not operate when the person is at rest
d) Explains the increased venous return when end-diastolic volume is
increased
e) Explains the increased stroke volume when end-diastolic volume is
increased
42. The work done by the right ventricle is much less than that done by the left
ventricle because its:
a) Wall is thinner
b) Stroke volume is less
c) Preload is less
d) Afterload is less
e) Systolic pressure is less
43. The following are not signs of pure right ventricular failure:
a) Increased central venous pressure
b) Central venous engorgement and pulsations
c) Pulmonary oedema
d) Hepatomegally
e) Sacral oedema
44. The blood vessel responsible for local regulation of blood flow in most tissues
is:
a) Distributing arteries
b) Large veins
c) Capillaries
d) Venules
e) Arterioles
45. The heart rate is increased by all the following except:
a) Fever
b) Increased venous return
c) Atropine
d) Hypothyroidism
e) Adrenaline
46. Stroke Volume:
a) Increases as a result of increased afterload
b) Equals end-diastolic volume minus end-systolic volume
c) Increases as heart rate is increased by electrical pacing


d) Is increased by parasympathetic stimulation
e) Is increased by Ca


2+ channel blocks


47. A drug that increases the heart rate from 70 to 100 beats per minute could
be:
a) Stimulation of B-1 adrenergic receptors
b) Inhibitor of alpha adrenergic receptors
c) Stimulation of muscarinic cholinergic receptors


d) Inhibitor B-2 adrenergic receptors
e) Digitalis
48. A high preload is indicated by:
a) Blood volume
b) Pulmonary pressure
c) End-diastolic volume
d) Systolic blood pressure
e) Diastolic blood pressure
49. Regurgitation of aortic valve leads to:
a) A decrease in diastolic pressure
b) A decrease in oxygen-consumption by the ventricles


c) A decrease in heart rate
d) A systolic murmur
e) A decreased end-systolic volume
50. Which of the following results in a decreased stroke volume?
a) An increase in end-diastolic volume
b) An increased afterload
c) Parasympathetic stimulation


d) A decrease in total peripheral resistance
e) Increased residual volume
51. An increase in pulse pressure can be caused by:
a) Parasympathetic stimulation
b) Generalized vasodilation
c) Severe hemorrhage
d) Aortic stenosis
e) Heart failure
52. On assuming the upright posture, one would expect:
a) Stimulation of Renin-angiotensin system
b) Increased pulmonary artery pressure
c) A decrease in pulse rate


d) Venodilation
e) An increase in renal blood flow
53. Central venous pressure increases:
a) In hypovolaemia
b) By sympathetic stimulation


c) When total peripheral resistance increases
d) When the cardiac output decreases
e) With increased sodium loss


54. Infusion of nor-adrenaline is expected to produce:
a) A decrease in firing-rate of baroreceptors
b) A reflex brachycardia


c) A decrease in total peripheral resistance
d) Increased myocardial contractility due to B2 receptors
e) An increase in cardiac output


55. Stroke volume is decreased when:
a) The sympathetic nerves are stimulated
b) The arterial blood pressure falls
c) Vagal centers are stimulated
d) The end-diastolic volume is increased
e) A patient stands up


56. Generalized vasoconstriction may be produced by:
a) Exposure to heat
b) Parasympathetic stimulation
c) An increase in vasomotor tone
d) When the depressor center is stimulated
e) An exposure to a large dose of histamine


57. Arterial vasoconstriction in a limb leads to:
a) An increase in capillary pressure
b) A decrease in arteriovenous oxygen difference
c) Diminished filteration in capillary bed
d) An increase in blood pH leaving the limb
e) Venoconstriction


58. Which of the following is the most important in determining the total
peripheral resistance?
a) Blood viscosity
b) Concentration of plasma protein
c) Arteriolar diameter
d) Cardiac Output
e) Metabolic autoregulation


59. Venodilation at rest leads to:
a) A decrease in venous return
b) A drop in arterial blood pressure
c) Flushing of the skin


d) A decrease in peripheral resistance
e) Increased capillary fluid exchange
60. Stroke Volume:
a) Is normally about 90mL
b) Depends on Bainbridge reflex
c) Decreases when the heart rate increases
d) Increases when the end-diastolic volume increases
e) Is mainly controlled by vagal fibers


61. Starling's Law of the heart describes the relationship between:
a) The heart rate and stroke volume
b) The end-diastolic volume cardiac output
c) The blood pressure and heart rate
d) The initial length of cardiac muscle fibers and force of contraction
e) Sympathetic stimulation stroke volume


62. Increased pressure in the carotid sinus leads to:
a) An increase in vasomotor tone
b) Increase in vagal tone
c) Reflex vasoconstriction
d) Venoconstriction
e) Tachycardia


63. In the jugular pulse wave the wave "C":
a) Occurs before the "a" wave
b) Is due to atrial systole
c) Closure of the atrioventricular valve
d) Co-asides with the atrial pulse wave
e) Is due to bulging of tricuspid valves


64. The first heart sound:
a) Is due to vibrations in the aorta on closure of the semilunar valves
b) Is caused by closure of tricuspid valve
c) Occurs at the end of isometric contraction of the ventricle
d) Is caused by closure of both atrioventricular valves
e) Is short of high pitch


65. The Cardiac output is:
a) The volume of blood pumped by the heart in one minute
b) Equal to the heart rate multiplied by the stroke volume
c) Measured by dilution method
d) Increased on standing up
e) Greater in left ventricle than the right


66. The chemoreceptors are found in:
a) The lungs
b) Glomus bodies
c) Aortic arch
d) Carotid sinus
e) Medulla
67. Local vasodilation can be produced by:
a) Neural reflexes
b) Myogenic autoregulation
c) An increase in PO2
d) A decrease in H+ concentration
e) Synthesis of ATP


68. The following are expected to increase the cardiac output except:
a) Eating
b) Adrenaline Infusion
c) Moderate rise in environmental temperature
d) A 10 degree rise in body temperature
e) Pregnancy


69. Regarding the cardiac cycle which of the following is incorrect?
a) The first heart sound occurs at the start of isovolumetric contraction
b) The "v" wave of atrial pressure occurs during diastole
c) The third heart sound occurs during ventricular diastole
d) The second heart sound occurs in late systole
e) Ventriculor systole continues after the end of the ECG wave


70. The Frank-Starling law explains all the following except:
a) Increase in cardiac with increase in venous return
b) Maintenance of stroke volume in the phase of increased afterload
c) Matching left ventricular output with right ventricular output
d) The increased contractility induced by sympathetic stimulation
e) The normal cardiac output in hypertensive patients


71. A drug that increases the heart rate from 70 to 100 beats per minute could
be:
a) A B1-adrenergic receptor antagonist
b) A cholinergic receptor antagonist
c) A cholinergic receptor agonist
d) A B2 adrenergic receptor agonist
e) A non-cholinergic, non-adrenergic agonist


72. Excitation of the ventricles:
a) Proceeds from the subendocardium to the subpericardium
b) Leads to excitation of the atria
c) Results from the action of norepinephrine on ventricular muscle
d) Occurs 2.2 seconds following atrial excitation
e) Results from pacemaker potentials in ventricular cells


73. AV nodal cells:
a) Exhibit action potentials characterized by rapid depolarization
b) Conduct impulses more slowly than either atrial or ventricular cells
c) Are capable of pacemaker activity at an intrinsic rate of 100 beat per minute


d) Exhibit increased permeability to Na+ during the prepotntial
e) Show a steep pre-potential when exposed to acetylcholine
74. Stroke Volume:
a) Increases as a result of increased afterload
b) Equals end-diastolic volume minus end-systolic volume
c) Increases as the heart rate is increased by electrical pacing
d) Is increased by parasympathetic stimulation
e) Is increased by Ca-channel blockers


75. Coronary blood flow of the left ventricle:
a) Is mainly regulated by sympathetic supply to coronary arterioles
b) Increases when sympathetic nerves to the heart are blocked
c) Is highest during systole because of myocardial activity
d) Increases when myocardial metabolism increases
e) All of the above are correct
76. The strength of myocardial contraction:
a) Increases as a result of increased afterload
b) Equals end-diastolic volume minus end-systolic volume
c) Increases as heart rate increases by electrical pacing
d) Is increased by parasympathetic stimulation
e) Is increased by calcium channel blockers
77. Increased arterial blood pressure leads to:
a) Decreased firing of carotid sinus baroreceptors
b) Increased sympathetic activity to the ventricles
c) Increased parasympathetic activity to the sinoatrial node
d) Increased parasympathetic activity to arterioles of skeletal muscles and skin
e) Increased parasympathetic stimulation to the ventricles
78. Which of the following is likely to cause postural hypotension?
a) Drugs that block muscarinic cholinergic receptors
b) Decreased firing rate of baroreceptors while standing


c) Exposure to cold environment


d) Drugs that block cholinergic receptors in skeletal muscle vessels
e) Drugs that activates cholinergic receptors in autonomic ganglia
79. Stimulation of parasympathetic nerves to the heart:
a) Causes tachycardia
b) Makes the prepotential more horizontal
c) Decreases the rate of potassium efflux in the sino-atrial node
d) Prolongs the refractory period
e) Shortens the duration of the cardiac cycle
80. The prepotential of the pacemaker is mainly due to:
a) Calcium influx in the early phase
b) Increased K+ efflux
c) Increased chloride influx
d) Decreased K+ efflux
e) Decreased Na+ influx
81. The vessels responsible for regulation of blood pressure:
a) Medium-size arteries
b) Small veins
c) Capillaries
d) Venules
e) Arterioles


82. The advantage of the Starling mechanism in the heart is to:
a) Decrease fluid loss from the cardiac capillaries
b) Ensure that the ventricles operate at an optimum length
c) Couple the efficiency of muscle contraction to the heart rate
d) Match the output of one ventricle to that of the other
e) Ensure that the right and left arterial pressure are equal
83. An increase in arterial pulse pressure is observed in association with:
a) Exposure to cold
b) An increased peripheral resistance
c) Hypothyroidism
d) An increased vagal activity
e) Muscular exercise
84. A decrease in carotid sinus pressure would lead to a decrease in:
a) Heart rate
b) Myocardial contractility
c) Total peripheral resistance
d) Capacity of venous system
e) Cardiac output
85. In the ECG, the QRS wave is due to:
a) Atrial contraction
b) Atrial depolarization
c) Ventricular depolarization
d) SA node depolarization
e) Ventricular contraction
86. In the ECG, the P wave denotes:
a) Atrial contraction
b) Atrial depolarization
c) Ventricular repolarization
d) SA node depolarization
e) Ventricular contraction
87. Stimulation of sympathetic nerves to the heart:
a) Causes tachycardia via alpha-adrenergic receptors
b) Makes the prepotential more horizontal
c) Decreases the rate of potassium efflux in the SA node
d) Prolongs the nodal delay
e) Has no effect on the duration of the cardiac cycle
88. Concerning the heart sounds:
a) The first heart sound is due to closure of the atrioventricular valves
b) The second heart sound is due to opening of the aortic and pulmonary
valves
c) The third heart sound is due to atrial systole
d) The first heart sound occurs at the beginning of the isovolumetric relaxation
phase
e) The second heart sound is followed by isovolumetric contraction phase


89. In the normal ECG the duration of PQ interval is usually:
a) 0.10 sec
b) 0.15 sec
c) 0.30 sec
d) 0.45 sec
e) 0.60 sec
90. Starling's Law of the heart:
a) States that at a given end-diastolic pressure, norepinephrine increases the
volume
b) States that increased end-diastolic volume leads to an increased stroke
volume
c) Is primarily the result of changes in the firing rate of sympathetic nerves to
the ventricles
d) Is independent of the venous return
e) Describes the myocardial response to an increased heart rate
91. In the heart, transmission of impulses is fastest in:
a) Atrial muscles
b) Bundle of His
c) Ventricular muscles
d) Purkinje fibers
e) AV nodal fibers
92. The force of contraction of cardiac muscle is a function of:
a) Initial muscle length
b) Body temperature
c) Duration of the action potential
d) End-systolic volume
e) Number of impulses that reach the muscle cell per unit time
93. The second heart sound occurs:
a) During protodiastole
b) During isovolumetric relaxation
c) During isovolumetric contraction
d) 0.5 seconds after the first heart sound
e) At the peak of ejection period
94. The P wave of the ECG:
a) Occurs during rapid atrial inflow
b) Follows the "a" wave of atrial pressure
c) Is essential for development of normal QRS complex


d) Occurs during ventricular diastole
e) Is prominent in atrial fibrillaton


95. Which is true of cardiac muscle:
a) All cardiac muscle cells have pacemaker potentials
b) The rate of cardiac muscle contraction is always set by nerves to the heart


c) Impulses spread easily from one muscle cell to another
d) Cardiac muscles look smooth under the microscope
e) Cardiac muscles have relatively short refractory periods compared to
skeletal muscles


96. Stimulation of the right vagus nerve:
a) Increases the heart rate
b) Increases arterial blood pressure
c) Has a reduced effect after administration of physostigmine
d) Has a reduced effect after administration of atropine
e) Has a reduced effect after administration of prornaolol


97. Which of the laws explain the relationship between vessel wall tension and
vessel radius:
a) Poiseuille's Law
b) Ohm's Law
c) Starling's Law
d) LaPlace's Law
e) Reynold's Law


98. Which of the following are not innervated by sympathetic nerves?
a) Large arteries
b) Arterioles
c) Venules
d) Capillaries
e) Large veins


99. Which of the following substances will be most likely to dilate systemic
arterioles:
a) Endothelin
b) ADH
c) Histamine
d) Noreadrenaline
e) Aldosterone


100. Resistance to venous return:
a) Is higher during exercise than at rest
b) Equals to the slope of the venous return curve
c) Is reduced by sympathetic stimulation
d) Increases by increase in circulatory filling pressure
e) Increased by constriction of arterioles


101. Closure of the aortic valve occurs at:
a) The end of isovolumetric contraction
b) The beginning of isometric relaxation
c) The end of systole
d) The end of rapid filling phase
e) The beginning of rapid ejection phase


102. An increase in the pulse pressure can be caused by:
a) Parasympathetic stimulation
b) Generalized vasodilation
c) Sympathetic stimulation
d) Venodilation
e) Heart failure


103. The contribution of atrial contraction to ventricular filling is greatest:
a) When sympathetic stimulation is pronounced
b) At rapid heart rates
c) When atria and ventricles contract simultaneously
d) During atrial fibrillation
e) During bradycardia


104. The baroreceptor reflex mainly regulates:
a) Stroke volume
b) Heart rate
c) Mean arterial blood pressure
d) Systolic blood pressure
e) Diastolic blood pressure


105. Which of the following is a characteristic of cardiac muscle?
a) It has a long refractory period compared to skeletal muscle
b) There are electrical synapses
c) Gap junctions cause limitation of depolarization


d) Has myosin but no actin molecules
e) There are para cellular spaces
106. Factors affecting the strength of ventricular muscle include:
a) Parasympathetic inhibition
b) The length of muscle fibers
c) The length of plateau phase
d) Sympathetic stimulation
e) End-systolic volume


107. Stimulation of parasympathetic supply to the heart results in:
a) Decrease K+ efflux in cardiac muscle
b) Increases Ca2+influx in SA node
c) Increased delay in AV node
d) An increase in Cl- influx
e) Opening of sodium channel


108. The following increase the cardiac output except:
a) Sympathetic stimulation
b) Venodilation
c) Fever
d) Anemia
e) Exercise


109. The cardiac output is increased:
a) By stimulation of sympathetic beta-1 receptors
b) Increased impedance in the aortic arch
c) By high pressure in the arterial system
d) By impulses through the glosso-pharygeal nerve (ix)


e) In hypothyroidisim
110. Ventricular Depolarization:
a) Follows immediately after the closure of atrioventricular valves
b) Occurs during mid systole
c) Depends on sympathetic stimulation
d) Occurs 0.2 sec following atrial excitation
e) Results from pacemaker cells in ventricular cells


111. The isovolumetric relaxation phase of the ventricles:
a) Is associated with rapid filling
b) Occurs during late diastole
c) Ends by opening of the atrioventricular valves
d) Results in falling of ventricular pressure by about 10 mmHg
e) Is marked by the first heart sound


112. Factors that increase the stroke volume include:
a) An increased afterload
b) A high end-diastolic volume
c) An increased heart rate
d) Parasympathetic stimulation
e) Ca2+ channel blockers


113. After a loss of one liter of blood:
a) The heart rate decreases slightly
b) Baroreceptors increase their discharge
c) The chemoreceptors have no role
d) The end diastolic volume increases
e) There is increased vasomotor tone


114. A large infarct affecting the left ventricle causes:
a) Pulmonary capillary hydrostatic pressure to decrease
b) Left ventricular end systolic pressure to increase
c) Heart rate to decrease
d) The systolic blood pressure to decrease
e) Congestion of the liver


115. The blood vessels responsible for exchange between plasma & interstitial
fluid are:
a) Distributing arteries
b) Large veins
c) The capillaries
d) The venules
e) Arterioles


116. Conduction velocity of cardiac impulse is slowest in:
a) Atrial myocardial fibers
b) AV nodal fibers
c) Purkinje fibers
d) Ventricular myocardial fibers
e) His bundle fibers


117. The contribution of atrial contraction to ventricular filling is greatest:
a) When vagal activity is pronounced
b) At rapid heart rates
c) When atria and ventricles contract simultaneously
d) During atrial fibrillation
e) Early during ventricular diastole


118. The most important function of the Starling mechanism in the heart is:
a) To decrease fluid loss from the cardiac capillaries
b) To ensure that the ventricles operate at an optimum length
c) To couple the efficiency of muscle contraction to the heart rate
d) To match the output of one ventricle to that of the other
e) To ensure that right and left atrial pressures are equal


119. The highest coronary blood flow occurs:
a) Early during systole
b) When the left ventricular pressure is high
c) At the beginning of isovolumetric contraction
d) Towards the end of ventricular diastole
e) At the beginning of diastole


120. Which of the following results in an increased stroke volume?
a) An increase in end-diastolic volume
b) An increased afterload
c) Parasympathetic stimulation
d) An increase in the heart rate
e) Venodilation
reaction:

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