Deck 9: A--Cardiac Physiology

Question 1

The plateau of the cardiac action potential results from the opening of voltage-gated slow ____ channels in the plasma membrane of the ____ cell.

A) sodium; contractile
B) potassium; autorhythmic
C) calcium; contractile
D) chloride; pacemaker
E) potassium; contractile

Answer 1

C

Question 2

The right half of the heart pumps blood through the ____ circuit and the left half pumps blood through the ____ circuit.

A) systolic; diastolic
B) coronary; pulmonary
C) systemic; pulmonary
D) pulmonary; systemic
E) systemic; coronary

Answer 2

D

Question 3

The chordae tendineae

A) keep the AV valves from everting during ventricular systole
B) hold the AV valves open during diastole
C) hold the right and left ventricles together
D) transmit the electrical impulse from the atria to the ventricles
E) contract when the ventricles contract

Answer 3

A

Question 4

The wall of the left ventricle is thicker than the wall of the right ventricle because the

A) left ventricle must pump much more blood than the right ventricle so it must have stronger walls
B) 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) left ventricle must pump the same amount of blood into a higher-resistance, higher-pressure system
D) right ventricle must create higher tension within its walls
E) left ventricle must pump oxygenated blood, which requires more energy than pumping deoxygenated blood

Question 5

The aortic valve

A) prevents the backflow of blood into the aorta during ventricular diastole
B) prevents the backflow of blood into the left ventricle during ventricular diastole
C) prevents the backflow of blood into the right ventricle during ventricular diastole
D) closes when the first heart sound is heard
E) none of these

Question 6

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 fibers
E) SA node

Question 7

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

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

Question 8

Which of the following statements about action potentials in the heart is correct?

A) The rising phase of the action potential in autorhythmic cells is due to a rapid Ca²⁺ influx.
B) The rising phase of the action potential in contractile cells is due to a rapid Na⁺ influx.
C) The plateau phase of the action potential in contractile cells is due to a slow Ca²⁺ influx.
D) The rising phase of the action potential in autorhythmic cells is due to a rapid Ca²⁺ influx, and the rising phase of the action potential in contractile cells is due to a rapid Na⁺ influx
E) all of these

Question 9

The AV nodal delay ensures that:

A) The atria contract and empty their contents into the ventricles prior to ventricular systole.
B) The ventricles contract prior to atrial systole.
C) Tetanic contractions of cardiac muscle are impossible.
D) Ventricular diastole occurs before systole.
E) Atrial diastole occurs before atrial systole.

Question 10

Choose a correct sequence of blood flow during one pass through the heart and lungs (some steps may have been omitted):

A) right atrium®bicuspid valve®pulmonary vein
B) aortic valve®right ventricle®lung
C) lung®pulmonary artery®left atrium
D) right ventricle®bicuspid valve®aortic valve
E) none of these

Question 11

Blood returning from the lungs

A) enters the right atrium
B) enters the left atrium
C) is poorly oxygenated
D) enters the right atrium and is poorly oxygenated
E) enters the left atrium and is poorly oxygenated

Question 12

The systemic circulation

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

Question 13

Semilunar valves

A) prevent backflow of blood from the ventricles to the atria
B) prevent backflow of blood from the atria to the ventricles
C) prevent backflow of blood from the ventricles to the arterial trunks
D) prevent backflow of blood from the arterial trunks to the ventricles
E) none of these

Question 14

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.
E) It is too small to be picked up by external recording electrodes.

Question 15

A lumen that contains blood with a comparatively higher concentration of oxygen is in the

A) right ventricle
B) inferior vena cava
C) pulmonary artery
D) pulmonary vein
E) coronary veins

Question 16

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

A) Excitation and contraction of the cardiac muscle fibers of each heart chamber should be coordinated to ensure efficient pumping.
B) The atria should be excited and contract before the onset of ventricular 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) Excitation and contraction of the cardiac muscle fibers of each heart chamber should be coordinated to ensure efficient pumping, and the atria should be excited and contract before the onset of ventricular contraction to ensure that ventricular filling is complete.
E) The atria should be excited and contract before the onset of ventricular contraction to ensure that ventricular filling is complete, and the right side of the heart should contract first to ensure that oxygenated blood is delivered to the heart before the left side contracts.

Question 17

The heart chamber that has the greatest work load is

A) the right ventricle
B) the left ventricle
C) the left atrium
D) the right atrium
E) both atria

Question 18

Which valve(s) prevent regurgitation of blood from a right ventricle to the atrium?

A) tricuspid
B) mitral
C) pulmonary
D) tricuspid and pulmonary
E) all of these

Question 19

Adjacent cardiac muscle cells are joined together end-to-end in the ventricles by

A) intercalated discs
B) sarcomeres
C) Purkinje fibers
D) sinoatrial nodes
E) atrioventricular nodes

Question 20

The primary function of the pericardial sac is to

A) prevent excessive expansion of the heart as it fills with blood
B) secrete a fluid that reduces friction as the heart beats
C) serve as a reservoir for blood to be used during strenuous exercise
D) provide oxygen and nutrients to the heart muscle
E) catch and kill any bacteria in the blood flowing through the heart chambers

Question 21

Depolarization occurs 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
E) during the T wave

Question 22

The normal pacemaker of the heart is the

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

Question 23

The refractory period of cardiac muscle

A) lasts almost as long as the contraction period
B) is much longer than the refractory period in skeletal muscle
C) prevents tetanic contraction of the heart to occur to ensure smooth, coordinated ejection of blood from the ventricles
D) all of these
E) lasts almost as long as the contraction period and is much longer than the refractory period in skeletal muscle

Question 24

The membrane potential of cardiac muscle cells at rest is about ____ mV.

A) -110
B) -90
C) -70
D) -50
E) -30

Question 25

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
E) murmurs

Question 26

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 terminate normally.
C) An ECG lead is attached on the outside of the chest.
D) A heart valve is attached.
E) The chordae tendineae attach to a valve.

Question 27

The direction of the impulse through the conduction system of the heart is normally:

A) AV node¾SA node¾bundle of His¾Purkinje fibers
B) AV node¾bundle of His¾SA node-¾Purkinje fibers
C) bundle of His¾AV node¾Purkinje fibers¾SA node
D) SA node¾AV node¾bundle of His¾Purkinje fibers
E) SA node¾bundle of His¾Purkinje fibers¾AV node

Question 28

The function of the ventricular conduction system of the heart is to

A) spread the action potential throughout the ventricle to ensure a single, coordinated contraction of the both ventricles
B) spread the action potential in the absence of sympathetic stimulation
C) spread the action potential throughout the atria and ventricles
D) slow down the original action potential so it has time to spread through the ventricles evenly
E) spread the action potential throughout the ventricle to ensure a single, coordinated contraction of the both ventricles, and slow down the original action potential so it has time to spread through the ventricles evenly

Question 29

Fibrillation is the

A) backflow of blood throughout the heart
B) coordinated function of nodal cells
C) failure of the heart valves to function
D) flow of blood through the heart's fibrous skeleton
E) uncoordinated excitation and contraction of cardiac cells

Question 30

The volume of blood ejected from each ventricle during a contraction is called the

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

Question 31

The fastest rate of autorhythmicity is normally carried out by the

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

Question 32

Why can't tetanus occur in the heart?

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 contraction.
D) The heart contracts with maximal force every beat so it is impossible to increase the strength of its contraction.
E) Vagal stimulation slows down the heart rate to prevent summation of contractions.

Question 33

The AV node

A) is the normal pacemaker of the heart
B) is the only electrical connection between the atria and the ventricles
C) rapidly conducts the impulse from the atria to the ventricles so that they contract simultaneously
D) is not innervated by the vagus nerve
E) has the slowest rate of depolarization in the heart

Question 34

Which is the normal sequence of the spread of cardiac excitation?

A) 2¾3¾1¾5¾4¾6
B) 3¾2¾1¾4¾5¾6
C) 2¾3¾1¾4¾5¾6
D) 1¾2¾3¾4¾5¾6
E) none of these

Question 35

Which of the following ECG waves represents ventricular repolarization?

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

Question 36

The function of the atrioventricular node is to

A) excite the left and right atrium
B) control the heart rate
C) prevent the atria and ventricles from contracting simultaneously
D) repolarize the heart after systole
E) none of these

Question 37

The QRS complex represents

A) depolarization of the atria
B) depolarization of the ventricles
C) the AV nodal delay
D) repolarization of the ventricles
E) the time during which the heart is contracting

Question 38

Extrasystole of the heart means that it

A) beats too slowly
B) fills with too much blood
C) has a complete block
D) loses blood
E) produces a premature beat

Question 39

The SA is the heart's normal pacemaker because

A) It has the fastest 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.
E) None of these.

Question 40

During isovolumetric phases of the cardiac cycle,

A) The atria are contracting.
B) All heart valves are closed.
C) Blood is being ejected into the aorta.
D) The ventricles can only be relaxing.
E) The atria are contracting and all heart valves are closed.

Question 41

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

A) 0%
B) 20%
C) 80%
D) 50%
E) 100%

Question 42

During isovolumetric contraction,

A) Rapid filling of the ventricles occurs.
B) No blood enters or leaves the ventricles.
C) The maximum volume of blood is ejected.
D) The maximum rate of ejection occurs.
E) Both the maximum volume of blood is ejected and the maximum rate of ejection occurs.

Question 43

Which of the following decreases ESV?

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

Question 44

Vagal influences on the heart result in

A) enhanced calcium permeability at the SA node
B) enhanced potassium permeability at the SA node
C) less frequent depolarization of the SA node
D) enhanced calcium permeability at the SA node and enhanced potassium permeability at the SA node
E) enhanced potassium permeability at the SA node and less frequent depolarization of the SA node

Question 45

The aortic valve opens

A) when ventricular pressure exceeds aortic pressure
B) at the start of ventricular systole
C) just after the isovolumetric relaxation phase
D) just before the isovolumetric contraction phase
E) none of these

Question 46

An insufficient AV valve

A) fails to open completely
B) is not connected to chordae tendineae
C) produces a gurgling diastolic murmur
D) allows blood to backflow into a ventricle during diastole
E) none of these

Question 47

The dicrotic notch on the aortic pressure curve is due to

A) a disturbance set up by the aortic valve closing
B) a disturbance set up when the AV valves close
C) elastic recoil of the aorta during ventricular diastole
D) turbulent flow through a stenotic valve
E) atherosclerosis in the aorta

Question 48

The heart

A) is sympathetically innervated via cardiac nerve fibers
B) is parasympathetically innervated by vagus nerve fibers
C) is innervated by the phrenic nerve
D) is innervated by only the sympathetic division of the autonomic nervous system
E) is sympathetically innervated via cardiac nerve fibers and is parasympathetically innervated by vagus nerve fibers

Question 49

Atrial flutter is characterized by a ____ rhythm, as impulses pass from the AV node to the ventricles.

A) 1:1
B) 2:1
C) 3:4
D) 5:2
E) 7:1

Question 50

When the heart is sympathetically stimulated,

A) ESV will increase.
B) It is responding to acetylcholine.
C) It is responding to norepinephrine.
D) Ca²⁺ channels are opening in greater numbers.
E) It is responding to norepinephrine, and Ca²⁺ channels are opening in greater numbers.

Question 51

Cardiac output

A) is the volume of blood pumped by each ventricle during each contraction or beat
B) is the volume of blood pumped by each ventricle per minute
C) equals heart rate x stroke volume
D) is the volume of blood pumped by each ventricle during each contraction or beat, and equals heart rate x stroke volume
E) is the volume of blood pumped by each ventricle per minute, and equals heart rate x stroke volume

Question 52

If the connection between the SA node and AV node becomes blocked,

A) The QRS complex will be absent on an ECG.
B) The ventricles will beat more slowly.
C) The atria will beat slower.
D) Tachycardia will occur.
E) The QRS complex will be absent on an ECG and tachycardia will occur.

Question 53

Which factor(s) would decrease cardiac output?

A) increased venous return
B) decreased vagal stimulation of the heart
C) increased preload
D) decreased preload
E) increased venous return and increased preload

Question 54

The first heart sound

A) occurs when the AV valves open
B) occurs when the semilunar valves close
C) signals the onset of ventricular diastole
D) occurs when the AV valves close, and signals the onset of ventricular systole
E) occurs when the semilunar valves close, and signals the onset of ventricular diastole

Question 55

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

A) is heart block
B) is fibrillation
C) can be treated with administration of an electrical current
D) is heart block and fibrillation
E) is fibrillation and can be treated with administration of an electrical current

Question 56

A heart valve opens and closes due to

A) being pulled by the heart muscle
B) pressure differences on the valve's two sides
C) Na⁺ and K⁺ fluxes during ventricular depolarization
D) turbulent flow in the atria and ventricles
E) none of these

Question 57

The cardiac output is equal to

A) (EDV - ESV) x HR
B) heart rate x EDV
C) the difference between the stroke volume at rest and the stroke volume during exercise
D) the stroke volume minus the ESV
E) heart rate x blood pressure

Question 58

The second heart sound is produced by the

A) opening of the AV valves
B) closing of the AV valves
C) opening of the semilunar valves
D) closing of the semilunar valves
E) blood rushing through the AV valves during diastole, creating a turbulent flow

Question 59

Which is true when your sympathetic nervous system is more active?

A) The SA node depolarizes more rapidly.
B) The myocardium repolarizes more rapidly.
C) More Ca²⁺ becomes available and causes more forceful heart contractions.
D) Norepinephrine is stimulating the heart.
E) All of these.

Question 60

The period lasting from closure of the AV valve to opening of the aortic valve is known as

A) isovolumetric ventricular contraction
B) isovolumetric ventricular relaxation
C) the rapid ejection phase
D) the rapid filling phase
E) none of these

Question 61

According to the Frank-Starling law of the heart,

A) Shortening cardiac muscle fibers prior to contraction causes a more forceful contraction.
B) Increasing venous return increases EDV, which leads to an increased stroke volume.
C) As cardiac output decreases, blood pools in the vasculature and increases arterial blood pressure.
D) The left ventricle must pump more blood than the right ventricle since the left ventricle must pump blood to more regions of the body.
E) The greater the stroke volume, the smaller the subsequent ESV, because as more blood is squeezed out, the heart cannot fill as completely.

Question 62

The right ventricle pumps deoxygenated blood through the tricuspid valve and into the pulmonary arteries.

Question 63

The parasympathetic nervous system has little effect on ____ activity.

A) atrial
B) AV node
C) heart rate
D) SA node
E) ventricular

Question 64

Vasodilation of coronary arteries is induced by

A) adenosine
B) nitroglycerin
C) nitric oxide
D) all of these
E) adenosine and nitroglycerin

Question 65

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

A) 150 ml/min
B) 560 ml/min
C) 5,600 ml/min
D) 8,700 ml/min
E) none of these

Question 66

Which of the following is not associated with an increase in stroke volume?

A) increased end-diastolic volume
B) increased contractility of the heart
C) increased end-systolic volume
D) increased preload
E) increased venous return

Question 67

If the EDV were held constant, increased cardiac output could be accomplished by

A) decreased sympathetic stimulation of the heart
B) decreased parasympathetic stimulation of the heart
C) decreased contractility
D) increased length of isovolumetric contraction
E) increased arterial blood pressure

Question 68

At rapid heart rates

A) Systole and diastole shorten equally.
B) Systole stays almost constant, but diastole shortens.
C) Systole lengthens and diastole shortens
D) Diastole lengthens and systole shortens.
E) None of these.

Question 69

A whistling murmur heard between the second and first heart sound would be indicative of

A) a stenotic AV valve
B) an insufficient AV valve
C) a myocardial infarction
D) an insufficient semilunar valve
E) No conclusions can be reached based on the information provided.

Question 70

If the cardiac output is 4,800 ml/min and the heart rate is 60 beats per minute, the stroke volume averages ____ ml.

A) 60
B) 70
C) 80
D) 120
E) 140

Question 71

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 EDV.
C) A compensatory increase in sympathetic activity increases the contractility of the heart to normal in the early stages of the disease.
D) All of these.
E) The heart pumps out a smaller stroke volume than normal for a given EDV, and a compensatory increase in sympathetic activity increases the contractility of the heart to normal in the early stages of the disease.

Question 72

Parasympathetic innervation to the heart:

A) involves the vagus nerve
B) decreases the rate at which the pacemaker potential reaches threshold
C) decreases the strength of ventricular contraction
D) all of these
E) involves the vagus nerve and decreases the strength of ventricular contraction

Question 73

Increased ____ permeability of nodal cells hyperpolarizes the SA node.

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

Question 74

The cardiac muscle

A) extracts oxygen and nutrients from the blood within its chambers
B) receives its blood supply primarily during ventricular systole when blood is forced into the vessels supplying the heart
C) receives its blood supply as all blood returning to the heart from the lung passes through the cardiac circulation before being pumped to the systemic circulation
D) receives most of its blood supply during ventricular diastole by means of the coronary circulation
E) none of these

Question 75

The pulmonary circulation carries oxygenated blood from the lungs through the coronary circulation and then into the aorta.

Question 76

The term systole means

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

Question 77

Twelve complete ECG patterns are recorded over 10 seconds, which means the heart rate is ____ beats per minute.

A) 60
B) 72
C) 90
D) 108
E) 120

Question 78

Select the incorrect statement about rheumatic fever.

A) It causes a heart murmur.
B) It is an autoimmune disease.
C) It is triggered by a streptococcus bacterium.
D) The heart conduction system is disrupted.
E) The heart valves become inflamed and scarred.

Question 79

Sympathetic stimulation of the heart

A) increases the heart rate
B) increases the heart's contractility
C) shifts the Frank-Starling curve to the left
D) involves the release of norepinephrine
E) all of these

Question 80

A metabolic predictor of heart disease that is independent of one's cholesterol/lipid profile is

A) HDL
B) VLDL
C) homocysteine
D) methionine
E) creatine