Deck 7: Cardiac Physiology

Question 1

Which 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 higher for the heart to function efficiently

Answer 1

A

Question 2

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 as 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

Answer 2

B

Question 3

Which statement is INCORRECT regarding fetal circulation?

A) The foramen ovale interconnects the atria.
B) The ligamentum arteriosum shunts blood from the pulmonary artery directly into the aorta.
C) The fetus has two lung bypasses.
D) The umbilical vein carries oxygen-rich blood to the fetus.

Answer 3

B

Question 4

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) Purkinjie fibres

Question 5

Which statement concerning action potentials in the heart is correct?

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 rapidCa2+ influx.
D) The plateau phase of the action potential in cardiac contractile cells is due to a rapid K+ influx.

Question 6

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.

Question 7

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

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

Question 8

Which heart chamber has the greatest workload?

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

Question 9

Which function is done by the aortic valve?

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

Question 10

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 11

What is the proper sequence of blood flow through the circulatory system?
1)right atrium 6)pulmonary vein
2)left atrium 7)lungs
3)right ventricle 8)systemic tissues
4)left ventricle 9)aorta
5)pulmonary artery 10)venae cavae

A) 1-2-3-4-5-6-7-8-9-10
B) 10-2-4-5-7-6-1-3-9-8
C) 10-1-3-5-7-6-2-4-9-8
D) 10-1-2-3-4-5-7-6-9-8

Question 12

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 13

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) pulmonary
D) systemic

Question 14

Which statement concerning the AV nodal delay is correct?

A) It ensures that the atria contract and empty their contents into the ventricles prior to ventricular systole.
B) It ensures that the ventricles contract prior to atrial systole.
C) It ensures that tetanic contraction of cardiac muscle is impossible.
D) It is shortened by parasympathetic stimulation.

Question 15

Which vessel carries blood with a comparatively high concentration of oxygen?

A) chordae tendineae
B) inferior vena cava
C) pulmonary artery
D) pulmonary vein

Question 16

Blood returning from the lungs _________________

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

Question 17

Which of the following 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 the electrical impulse from the atria to the ventricles

Question 18

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

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

Question 19

Which action is done by the semilunar valves?

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

Question 20

Which statement is correct for the systemic circulation?

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

Question 21

The refractory period of cardiac muscle ________________________

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

Question 22

When does electrical activity occur at the AV node?

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

Question 23

Which of the following is the normal pacemaker of the heart?

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

Question 24

Which of the following is INCORRECT about cardiac muscle cells?

A) 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 25

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 26

Which statement is correct for 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 27

What does extrasystole of the heart mean?

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

On an electrocardiogram,what represents depolarization of the ventricles?

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

Question 29

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 lies in the right atrium.
D) Activation of K+ channels occurs more rapidly in this region than elsewhere in the heart.

Question 30

What is the function of the atrioventricular node?

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

Question 31

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 32

Why can't tetany of the heart occur in normal condition?

A) There are no distinct motor units in the heart.
B) There is inadequate oxygen supply via the coronary circulation to metabolically support a sustained contraction.
C) The refractory period in cardiac muscle lasts almost as long as the duration of the resultant contraction.
D) The heart contracts with maximal force every beat so it is impossible to increase the strength of cardiac contraction.

Question 33

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

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

Question 34

What is the membrane potential of cardiac muscle cells at rest?

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

Question 35

Which of the following 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 36

What normally carries out the fastest rate of autorhythmicity?

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

Question 37

An ectopic focus is the place where __________________________

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

Question 38

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 39

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

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

Question 40

Which statement concerning the AV node is correct?

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 41

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 42

What happens during the isovolumetric phase of ventricular systole?

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

Question 43

Although the heart does not require the nervous system to initiate contraction events _______________

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

Question 44

Why do the heart valves open and close?

A) They are attached to the heart muscle.
B) There is a pressure difference on the two sides of the valve.
C) Na+ and K+ fluxes occur during ventricular depolarization.
D) There is turbulent flow in the atria and ventricles.

Question 45

Which of the following does NOT negatively influence the myocardium's contractility,thus increasing ESV?

A) acetylcholine
B) preload
C) afterload
D) parasympathetic activity

Question 46

What is 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 atria into ventricles

Question 47

Which of the following is correct for the first heart sound?

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

Question 48

What 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 49

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 50

The cardiac output is equal to ________________________

A) the difference between the end-diastolic volume (EDV) and the end-systolic volume (ESV) ?6? 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) the stroke volume less the end-systolic volume

Question 51

What is the result of vagal influences on the heart?

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

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

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

A) is probably heart block.
B) is probably fibrillation.
C) can be treated with administration of an electrical current.
D) is called bradycardia.

Question 54

What happens when the heart is sympathetically stimulated?

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

Question 55

What happens during isovolumetric ventricular contraction?

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

Question 56

When does the aortic semilunar valve open?

A) when ventricular pressure exceeds aortic pressure
B) at the start of systole
C) at the maximum ventricular pressure
D) immediately after atrial contraction

Question 57

What is the term for 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 58

What happens if the connection between the SA node and AV node becomes blocked?

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

Question 59

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

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

Question 60

A cardiac muscle cell contraction averages about how many msec in duration?

A) 50
B) 100
C) 150
D) 300

Question 61

What 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 62

What happens during heart failure?

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

Question 63

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 64

What does sympathetic stimulation of the heart do?

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

Question 65

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 66

Parasympathetic innervation to the heart _______________________

A) is the spinal nerve
B) decreases the rate at which spontaneous action potentials are initiated in the SA node
C) decreases the strength of ventricular contraction
D) increases the heart rate

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

What does a whistling murmur heard between the second and first heart sound 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 69

What happens in an insufficient AV valve?

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

Question 70

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 71

If 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) 5,600 mL/min.
D) 8,700 mL/min.

Question 72

If the cardiac output is 4,800 mL/min and the heart rate is 60 beats per minute,how many millilitres does the stroke volume average?

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

Question 73

Which nerves to the heart alter cardiac output by increasing heart rate and increasing contractility?

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

Question 74

Which of the following 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 75

What does the Frank-Starling law of the heart state?

A) The shorter the initial length of the cardiac muscle fibres prior to contraction, the more forceful will be the subsequent contraction because the fibres are already partially contracted.
B) Increasing the venous return increases the end-diastolic volume, which leads to an increased stroke volume, so the heart normally pumps out all of the blood returned to it.
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 because the right side pumps blood only to the lungs, whereas the left side must pump blood to the rest of the body.

Question 76

Increased _____ permeability of nodal cells hyperpolarizes the SA node.

A) chloride
B) iodide
C) potassium
D) sodium

Question 77

What does the term systole mean?

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

Question 78

The parasympathetic nervous system has little effect on what type of activity?

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

Question 79

Which of the following is INCORRECT about rheumatic fever?

A) It may cause a heart murmur.
B) It is an autoimmune disease.
C) It is triggered by a streptococcus bacterium.
D) The heart conduction system is initially destroyed.

Question 80

Which of the following 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