Deck 8: Cardiac Physiology

Question 1

According to the text, why is the wall of the left ventricle thicker than the wall of the right ventricle

A)The left ventricle must pump much more blood than the right ventricle, so it must have stronger walls.
B)The right ventricle must pump much more blood than the left ventricle, so it has a larger chamber to accommodate the blood and a correspondingly thinner wall.
C)The left ventricle must pump the same amount of blood into the high-resistance, high-pressure systemic system as does the right ventricle into the low-resistance, low-pressure pulmonary system.
D)The right ventricle must create higher tension within its walls.

Answer 1

C

Question 2

Which of the following is the normal pacemaker of the heart

A)SA node
B)AV node
C)bundle of His
D)Purkinje system

Answer 2

A

Question 3

Which of the following describes blood returning from the lungs

A)It enters the right atrium.
B)It enters the left atrium.
C)It is poorly oxygenated.
D)It enters the left ventricle.

Answer 3

B

Question 4

Which of these actions is done by the chordae tendineae

A)keeping the AV valves from closing during ventricular contraction
B)holding the AV valves open during diastole
C)holding the right and left ventricles together
D)transmitting electrical impulses from the atria to the ventricles

Question 5

Why is the sinoatrial node the heart's normal pacemaker

A)It has the fastest natural rate of autorhythmicity.
B)It has both sympathetic and parasympathetic innervation.
C)It is under the control of AV node.
D)Activation of K⁺ channels occurs more rapidly in this region than elsewhere in the heart.

Question 6

Which of these statements refers to the Frank-Starling law of the heart

A)The shorter the initial length of the cardiac muscle fibres prior to contraction, the more forceful will be the subsequent contraction.
B)Increasing the venous return increases the end-diastolic volume, which leads to an increased stroke volume.
C)As cardiac output is reduced, blood pools in the vasculature so that arterial blood pressure increases.
D)The output of the left side of the heart must always exceed that of the right side of the heart.

Question 7

Which of these statements describes the AV node

A)It is the normal pacemaker of the heart.
B)It is the only electrical connection between the atria and the ventricles.
C)It rapidly conducts the impulse from the atria to the ventricles so that they contract simultaneously.
D)It is not innervated by the vagus.

Question 8

Which cardiac valve prevents regurgitation of blood from the right ventricle to the atrium

A)tricuspid
B)mitral
C)bicuspid
D)aortic

Question 9

Which of the actions is done by the semilunar valves

A)prevention of backflow of blood from the ventricles to the atria
B)prevention of backflow of blood from the atria to the ventricles
C)prevention of backflow of blood from the ventricles to the arterial trunks
D)prevention of backflow of blood from the arterial trunks to the ventricles

Question 10

Which vessel carries blood with a comparatively high concentration of oxygen

A)superior vena cava
B)inferior vena cava
C)pulmonary artery
D)pulmonary vein

Question 11

Which of these statements describes the systemic circulation

A)It receives more blood than the pulmonary circulation.
B)It receives blood from the right ventricle.
C)It receives blood from the right atrium.
D)It is a high-pressure system compared to the pulmonary circulation.

Question 12

What component of the cardiac conduction system distributes electrical signals through the papillary muscles directly

A)AV nodes
B)AV bundle
C)bundle of His
D)Purkinje fibres

Question 13

Which heart chamber has the greatest workload

A)right ventricle
B)left ventricle
C)left atrium
D)right atrium

Question 14

Which of the following is a function of the aortic valve

A)to prevent backflow of blood into the aorta during ventricular diastole
B)to prevent backflow of blood into the left ventricle during ventricular diastole
C)to prevent backflow of blood into the right ventricle during ventricular diastole
D)to close when the first heart sound is heard

Question 15

Which structures join adjacent cardiac muscle cells end-to-end in the ventricles

A)intercalated discs
B)sarcomeres
C)Purkinje fibres
D)sinoatrial nodes

Question 16

Which of these statements does NOT describe cardiac muscle cells

A)Either all of them contract in the heart or none of them contract.
B)They are capable of graded strength of contraction.
C)They are produced constantly after infancy.
D)They have an abundance of mitochondria.

Question 17

Which structure is the low-resistance pathway that permits electrical activity to pass from cell to cell in myocardial tissue

A)desmosome
B)septum
C)gap junction
D)T-tubule

Question 18

Which of these statements applies to the cardiac muscle

A)Its muscle fibers are non-striated with many nuclei.
B)It receives its blood supply primarily during ventricular systole.
C)It receives its blood supply as the blood returning to the heart from the lung.
D)It receives most of its blood supply during ventricular diastole.

Question 19

What is the primary function of the pericardial sac

A)to prevent excessive expansion of the heart as it fills with blood
B)to secrete a fluid that reduces friction while the heart beats
C)to serve as a reservoir for blood to be used during strenuous exercise
D)to provide oxygen and nutrients to the heart muscle

Question 20

The right half of the heart pumps blood through the pulmonary circuit.Through which circuit does the left half pump blood

A)diastolic
B)pulmonary
C)systolic
D)systemic

Question 21

On a normal ECG, a wave for repolarization of the atria is not recorded.Why

A)The leads are not placed in a position to pick it up.
B)No repolarization of the atria occurs normally.
C)It occurs simultaneously with ventricular depolarization and is masked by the QRS complex.
D)It does not travel through body fluids.

Question 22

Twelve complete ECG patterns are recorded from a subject over 10 seconds.If this pattern continues, what is the rate of the heartbeat in the subject

A)60 beats per minute
B)72 beats per minute
C)90 beats per minute
D)108 beats per minute

Question 23

Which of these ECG waves represents ventricular repolarization

A)P wave
B)QRS complex
C)T wave
D)Ventricular repolarization occurs simultaneously with atrial depolarization and consequently cannot be recorded.

Question 24

What is the function of the atrioventricular node

A)to excite the left and right atria
B)to control the heart rate
C)to prevent the atria and ventricles from contracting simultaneously
D)to repolarize the heart after systole

Question 25

When does electrical activity occur at the AV node

A)during the P wave
B)between the P wave and the QRS complex
C)during the QRS complex
D)between the QRS complex and the T wave

Question 26

Which of these events will happen if the connection between the SA node and the AV node becomes blocked

A)The ventricles will beat faster.
B)The stroke volume will increase.
C)The ventricular rate of contraction will not be affected.
D)The ventricles will contract more slowly.

Question 27

Which of these statements applies to extrasystole of the heart

A)The heart beats too slowly.
B)The heart fills with too much blood.
C)The heart has a complete heart block.
D)The heart produces a premature beat.

Question 28

What is the function of the ventricular conduction system of the heart

A)to spread the action potential throughout the large ventricular mass to ensure a single, coordinated contraction of the ventricles
B)to spread the action potential in the absence of sympathetic stimulation
C)to set the heart rate
D)to spread the action potential throughout the atria and ventricles

Question 29

Which of these statements describes action potentials in the heart

A)The rising phase of the action potential in cardiac autorhythmic cells is due to a rapid Ca²⁺ influx.
B)The rising phase of the action potential in cardiac contractile cells is due to a rapid K⁺ influx.
C)The plateau phase of the action potential in cardiac contractile cells is due to a rapid Ca²⁺ influx.
D)The plateau phase of the action potential in cardiac contractile cells is due to a rapid K⁺ influx.

Question 30

What is the purpose of the AV nodal delay

A)to ensure that all blood from the atria flows into the ventricles prior to ventricular systole
B)to ensure that all blood from the ventricles flows into the atria prior to atrial systole
C)to ensure that tetanic contraction of cardiac muscle is not possible
D)to ensure that heart rate slows down by parasympathetic stimulation

Question 31

Cardiac tetany never occurs under normal conditions for which of these reasons

A)because there are no distinct motor units in the heart
B)because there is inadequate oxygen supply via the coronary circulation
C)because of the long duration of cardiac muscle's refractory period preventing summation of contraction
D)because the heart contracts with maximal force every beat, increasing the strength of the cardiac contraction

Question 32

Which of the following normally carries out the fastest rate of autorhythmicity

A)AV bundle
B)AV node
C)bundle of His
D)SA node

Question 33

What is the membrane potential of cardiac muscle cells at rest

A)-110 mV
B)-90 mV
C)-60 mV
D)-50 mV

Question 34

Which of the following occurrences causes the dicrotic notch on the aortic pressure curve

A)a disturbance set up during closure of the aortic valve
B)a disturbance set up during closure of the left atrioventricular valve
C)elastic recoil of the arterial walls during ventricular diastole
D)turbulent flow through a stenotic valve

Question 35

Which of these statements refers to the refractory period of cardiac muscle

A)It lasts longer than the contraction period.
B)It is much longer than the refractory period in skeletal muscle.
C)It allows tetanic contraction of the heart to occur to ensure smooth, coordinated ejection of blood from the ventricles.
D)It lasts longer than the relaxation period.

Question 36

Which of the following occurs when an individual is sympathetically stimulated

A)The SA node depolarizes more rapidly.
B)More ATP results in more sarcomere cross-bridge attachments.
C)Ventricles contract harder than atria.
D)The SA node repolarizes more slowly.

Question 37

What does the QRS complex represent

A)depolarization of the atria
B)depolarization of the ventricles
C)the AV nodal delay
D)repolarization of the ventricles

Question 38

Which of these criteria must be met for the heart to function efficiently

A)Excitation and consequently contraction of the cardiac muscle fibres of each heart chamber should be coordinated to ensure efficient pumping.
B)The ventricles should be excited and contract before the onset of atrial contraction to ensure that ventricular filling is complete.
C)The right side of the heart should contract first to ensure that oxygenated blood is delivered to the heart before the left side contracts.
D)The fluid pressure in the pericardial cavity must be high for the heart to function efficiently.

Question 39

What is the normal sequence of the spread of cardiac excitation

A)SA node, atria, AV node, bundle of His, Purkinje fibres, ventricular myocardium
B)Atria, SA node, AV node, Purkinje fibres, bundle of His, ventricular myocardium
C)SA node, atria, AV node, Purkinje fibres, bundle of His, ventricular myocardium
D)AV node, SA node, Atria, Purkinje fibres, bundle of His, ventricular myocardium

Question 40

What is the normal direction of the impulse through the conduction system of the heart for each cardiac cycle

A)AV node to SA node to bundle of His to Purkinje fibres
B)AV node to bundle of His to SA node to Purkinje fibres
C)bundle of His to AV node to Purkinje fibres to SA node
D)SA node to AV node to bundle of His to Purkinje fibres

Question 41

Which of the following happens during isovolumetric ventricular contraction

A)The ventricles fill rapidly.
B)No blood enters or leaves the ventricles.
C)The maximum volume of blood is ejected.
D)The maximum rate of ejection occurs.

Question 42

A condition in which the heart is contracting in an uncontrolled, rapid, and irregular manner is _______________

A)probably heart block.
B)probably fibrillation.
C)called tachycardia
D)called bradycardia.

Question 43

Which of these statements describes why the heart valves open and close

A)There is prolonged calcium influx.
B)There is turbulent flow in the atria and ventricles.
C)Na+ and K⁺ fluxes occur during ventricular depolarization.
D)There is a pressure difference on the two sides of the valve.

Question 44

Which of these events occurs at rapid heart rates

A)The lengths of systole and diastole shorten equally.
B)The length of systole stays almost constant, but the length of diastole shortens considerably.
C)The length of systole increases at the expense of diastolic time shortening.
D)Diastolic time lengthens, and systolic time shortens.

Question 45

On an electrocardiogram, what represents depolarization of the ventricles

A)P wave
B)T wave
C)S wave
D)QRS complex

Question 46

Which of these statements describes ectopic focus

A)the place where an abnormally excitable area of the heart initiates a premature action potential
B)the place where all the electrical impulses of the heart normally terminate
C)the place where an ECG lead is attached on the outside of the chest
D)the place where a heart valve is attached

Question 47

Which of these terms refers to the volume of blood ejected from each ventricle during a contraction

A)end-diastolic volume
B)end-systolic volume
C)stroke volume
D)cardiac output

Question 48

What does a whistling murmur heard between the first and second heart sounds indicate

A)a stenotic AV valve
B)an insufficient AV valve
C)a stenotic aortic or pulmonary semilunar valve
D)an insufficient aortic or pulmonary semilunar valve

Question 49

Which of the following actions produces the second heart sound

A)opening of the AV valves
B)closing of the AV valves
C)opening of the semilunar valves
D)closing of the semilunar valves

Question 50

What rhythm characterizes atrial flutter as impulses pass from the AV node to the ventricles

A)1:1
B)2:1
C)3:4
D)5:2

Question 51

Which of these terms refers to the term systole

A)closure
B)conduction
C)contraction
D)opening

Question 52

What is the term for the period lasting from closure of the AV valve to opening of the aortic valve

A)isovolumetric ventricular contraction
B)isovolumetric ventricular relaxation
C)the rapid ejection phase
D)the rapid filling phase

Question 53

What percentage of ventricular filling is normally accomplished before atrial contraction begins

A)0 percent
B)20 percent
C)50 percent
D)80 percent

Question 54

Which of these statements describes cardiac fibrillation

A)backflow of blood throughout the heart
B)coordinated function of nodal cells
C)failure of the heart valves and blood vessels to function
D)uncoordinated excitation and contraction of cardiac cells

Question 55

Which of the following describes the first heart sound

A)It occurs when the AV valves open.
B)It occurs when the semilunar valves close.
C)It signals the end of ventricular systole.
D)It signals the onset of ventricular systole.

Question 56

Which of these events happens in an insufficient AV valve

A)The AV valve fails to open completely.
B)The AV valve produces a gurgling diastolic murmur.
C)The AV valve produces a gurgling systolic murmur.
D)The AV valve fails to close completely.

Question 57

The second heart sound occurs when the semilunar valves close.What does this mark

A)the start of the ejection period
B)the start of systole
C)the end of the ejection period
D)the start of isovolumetric contraction

Question 58

The electrocardiogram is most useful in determining which component of cardiac output

A)stroke volume
B)end-diastolic volume
C)ejection fraction
D)heart rate

Question 59

When does the aortic semilunar valve open

A)when ventricular pressure exceeds aortic pressure
B)when systole starts
C)when ventricular pressure is maximum
D)immediately after atrial contraction

Question 60

Which of these events is happening during the isovolumetric phase of ventricular systole

A)The ventricles are relaxed isometrically.
B)The atrioventricular valves and semilunar valves are closed.
C)Blood is being ejected into the great vessels.
D)Venous blood is flowing back to the heart.

Question 61

A mitral valve damaged by rheumatic fever fails to open completely.What is this called

A)mitral stenosis
B)complete heart block
C)myocardial ischemia
D)mitral incompetence

Question 62

If the cardiac output is 4800 mL/min and the heart rate is 60 beats per minute, what is the average stroke volume in millilitres

A)60 mL
B)70 mL
C)80 mL
D)120 mL

Question 63

Which of these statements describes cardiac output

A)the volume of blood pumped by each ventricle during each contraction or beat
B)the volume of blood pumped by each ventricle per minute
C)stroke volume × SVR (systemic vascular resistance)
D)the volume of blood pumped by each atrium into ventricles

Question 64

Which of these events occurs due to sympathetic stimulation of the heart

A)The heart rate decreases.
B)The contractile strength of the heart muscle increases.
C)The Frank-Starling curve shifts to the right.
D)Cardiac output decreases.

Question 65

Which of these molecules induces vasodilation of coronary arteries

A)oxygen
B)adenosine diphosphate
C)nitric oxide
D)carbon dioxide

Question 66

Which of the following is a compensatory mechanism that comes into play in order to maintain the cardiac output for the failing heart

A)decreased myocardial contractility
B)increased vagal stimulation
C)increased sympathetic stimulation
D)peripheral vasodilation

Question 67

Which of the following is the cranial nerve of the parasympathetic nervous system that signals the heart

A)cardiac
B)coronary
C)trigeminal
D)vagus

Question 68

Which of these situations will NOT increase stroke volume

A)increased end-diastolic volume
B)increased contractility of the heart
C)increased end-systolic volume
D)increased stretch of the cardiac muscle fibres during ventricular filling

Question 69

The parasympathetic nervous system has little effect on which of these types of activity

A)atrial activity
B)AV node activity
C)SA node activity
D)ventricular muscle activity

Question 70

Which of these events happens when the heart is sympathetically stimulated

A)ESV increases.
B)Norepinephrine is released from neurons.
C)K2+ channels open in greater numbers.
D)Cardiac output decreases.

Question 71

Patients with diastolic heart failure would present with ____________________

A)failure of the ventricles to fill normally.
B)decreased cardiac contractility.
C)their heart pumping out more blood than it should with each contraction.
D)their heart muscle relaxing longer than it should with each contraction.

Question 72

Which of these actions happens during heart failure

A)The Frank-Starling curve is shifted to the left.
B)Blood flows faster in the arterioles.
C)A compensatory decrease in sympathetic activity increases the relaxation of the heart to normal in the early stages of the disease.
D)The heart pumps out a smaller stroke volume than normal for a given end-diastolic volume.

Question 73

If the EDV were held constant, what could accomplish increased stroke volume

A)increased sympathetic nerve activity to the heart
B)increased parasympathetic nerve activity to the heart
C)decreased contractility
D)increased arterial blood pressure

Question 74

A patient has an EDV of 85 mL and an ESV of 35 mL with a heart rate of 50.What is this patient's cardiac output

A)2500 mL/min, or 2.5 L/min
B)3500 mL/min, or 3.5 L/min
C)4500 mL/min, or 4.5 L/min
D)6500 mL/min, or 6.5 L/min

Question 75

Which of the following factors will NOT increase cardiac output

A)increased venous return
B)increased parasympathetic stimulation
C)increased preload
D)increased heart rate

Question 76

Which of these nerves to the heart alters cardiac output by increasing heart rate and contractility

A)motor
B)sensory
C)sympathetic
D)parasympathetic

Question 77

Cardiac output is equal to which of the following

A)the difference between end-diastolic volume (EDV) and end-systolic volume (ESV× HR)
B)the product of heart rate and EDV
C)the difference between the stroke volume at rest and the stroke volume during exercise
D)stroke volume minus end-systolic volume

Question 78

If the stroke volume is 80 mL and the heart rate is 70 beats per minute, what is the cardiac output

A)150 mL/min
B)560 mL/min
C)5600 mL/min
D)8700 mL/min

Question 79

Why the heart does not require the nervous system to initiate contraction events

A)because it is parasympathetically innervated via cardiac nerve fibres
B)because it is parasympathetically innervated by vagus nerve fibres
C)because it is innervated by the sympathetic division of the autonomic nervous system only
D)because it is innervated by cortical nerve fibres

Question 80

Which of the following is the result of vagal influences on the heart

A)enhanced potassium permeability at the SA node
B)enhanced calcium permeability at the SA node
C)more frequent depolarization of the SA node
D)stimulation of the heart by epinephrine