ANATOMY AND PHYSIOLOGY II
Chapter # 20 Cardiovascular System. Heart
Chapter # 20 The Heart
Anatomy of The Heart
1. List the major functions of the heart
1.Generating blood pressure
2.Routing blood
3.ensuring one-way blood flow
4. regulating blood supply
2. Cite the size, shape, and location of the heart
-The size of the heart is like the size of a closed fist, the average mass is
250g in females and 300 in males. It’s shape is similar to a blunt cone
-The heart is in the apex, the larger flat part of the opposite end of the heart
is the base.
3. Explain why knowing the heart’s location is important
The heart’s location is n the mediastinum, its important for health
professionals to know where the heart is due to the positioning of a
stethoscope, that way they can hear heart sounds and can position electrodes
to record an electrocardiogram from the chest.
4. Describe the structure of Pericardium
-The pericardium is a double layered closed sac that surrounds the heart. It
consists of two layers, the outer fibrous pericardium and the inner serous
pericardium. The fibrous pericardium is a tough fibrous connective tissue
layer.
5. List the layers of the heart and describe the function of each
The three layers of the heart is the epicardium, myocardium and the
endocardium.
-Epicardium is the superficial layer of the heart.
-Myocardium is the thick middle layer of the heart it is composed of cardiac
muscle cells and is responsible for the hearts ability to contract.
-The endocardium is deep into the myocardium, it consist of simple
squamous epithelium over a layer od connective tissue. The endocardium
covers the surfaces of the heart valves ad also allows blood to move easily
through the heart.
6. List the large veins and arteries that enter and exit the heart
-The superior vena cava and the inferior vena cava carry blood from the
body to the right atrium. Also the smaller coronary sinus carries blood from
the walls of the heart to the right atrium. Four pulmonary veins carry blood
from the lungs to the left Altium.
-Blood leaves the ventricles of the heart through two arteries: the pulmonary
trunk and the aorta.
-The right and left coronary arteries exit the aorta just above the point where
the aorta leaves the heart.
7. Review the structure and functions of the chambers of the heart
-The heart has four chambers, in where blood flows. Two atria and two
ventricles.
-The right atrium received oxygen poor blood from the body and pumps it
into the right ventricle
-The right ventricle pumps oxygen poor blood to the lungs.
-The left atrium received oxygen-rich blood from the lung’s ad pumps in
into the left ventricle
-The left ventricle pumps the oxygen-rich blood to the body.
8. Name the valves of the heart and state their locations and functions.
The atrioventricular valve is in each atrioventricular canal and is composed
of cusps or flaps. The atrioventricular valves ensure blood flows from the
atria into the ventricles, preventing blood from flowing back into the atria
-The tricuspid is between the right and the right ventricle valve.
-The atrioventricular valve between the left atrium and the left ventricle is
called the bicuspid valve (another term is mitral valve)
-The semilunar valves are identified by the great artery in which is located
and include the aortic semilunar valve and pulmonary semilunar valve. They
effectively closes the semilunar valves and prevents blood from flowing
back into the ventricles.
9. Describe the Coronary arteries and the Coronary circulation
-The coronary circulation consists of blood vessels that carry blood to and
from tissues of the heart wall.
-The right and left coronary arteries exit the aorta just above the point where
the aorta leaves the heart.
10.Relate the structural and functional characteristics of the cardiac muscles
cell.
-The myocardium is thick, middle layer of the heart. It is composed of
cardiac muscle cells and is primary responsible for the hearts ability to
contract.
11.Explain and describe the Conduction System of the Heart
The conduction system of the heart is composed of specialized cardiac
muscle cells that produce spontaneous action potentials. It also ensures the
conduction the proper pattern of contractions if the atria and ventricle,
maintaining normal blood flow.
12. Explain and describe the Cardiac Cycle of the Heart
The cardiac cycle refers to the repetitive pumping process that begins with
the onset of cardiac muscle contraction and ends with the start of the next
contraction.
13.Discuss the heart sounds and their significance
-The first heart sounds is a low pitched sound, it happens in the beginning of
ventricular systole and is caused by vibration of the atrioventricular valves
and surrounding fluid as the valves close.
-The second heart sound is a higher pitched sound; it occurs in the start of
ventricular diastole and results from closure of the aortic and pulmonary
semilunar valves.
-The third heart sound is faint it is caused by blood flowing in a turbulent
fashion into the ventricles, it can be detected near the end of the first onethird of diastole, during passive ventricular filling.
14.List the events that occur during the Cardiac Cycle.
-Atrial contraction begins the cardiac cycle, is the atria contacts they carry
out the primer pump function by forcing more blood into the ventricles.
-The action potential passes to the AV node, down the av bundle branches
and purkinje fibers, stimulating ventricular systole. This electrical activity is
represented as the QRS complex of an ECG. As the ventricles contract,
ventricular pressure increases, causing blood to flow towards the atria and
close the AV valves. Recall that the semilunar valves are closed at this point
as well. Ventricular contraction continues and ventricular pressure builds
until it overcomes the pressure in the pulmonary trunk and aorta.
-Ventricular repolarization leads to ventricular diastole. As ventricular
diastole begins the ventricle relax and ventricular pressure decreases below
the pressure in the pulmonary trunk and aorta.
-Atrial diastole began during ventricular systole, and as the atria relaxed,
blood flowed into them from the veins. As the ventricles continue to relax
ventricular pressure drop below atrial pressures, and the valve open. Passive
ventricular filling begins again.
-Once the ventricle have fully relaxed the state of the heart is the same as
when the cardiac cycle began. All chambers are relaxed, the AV valves are
open, and the semilunar valves are closed. With the next stimulus from the
SA node another cardiac cycle will begin.
15.Define Systole and Diastole
Diastole: means to dilate
Systole: means to contract
16.What produce the First and Second sound of the heart
The pumping heart produces distinct sounds, the first heart sound occurs at
the start of ventricular systole and caused by vibration of the atrioventricular
valves. The second sounds occur at the start if ventricular diastole and
results from closure of the aortic and pulmonary semilunar valves.
Blood Flow through the Heart
1. Describe and explain the blood flow through the heart. Left and Right side.
Electrophysiology of the Heart
2. Define action Potential, and describe action potential in cardiac muscle
An action potential is a rapid rise and subsequent fall in voltage or membrane potential
across a cellular membrane with a characteristic pattern. Sufficient current is required to
initiate a voltage response in a cell membrane; if the current is insufficient to depolarize
the membrane to the threshold level, an action potential will not fire. Examples of cells
that signal via action potentials are neurons and muscle cells.
1.Stimulus starts the rapid change in voltage or action potential. In patch-clamp mode, sufficient
current must be administered to the cell in order to raise the voltage above the threshold voltage
to start membrane depolarization.
2.Depolarization is caused by a rapid rise in membrane potential opening of sodium channels in
the cellular membrane, resulting in a large influx of sodium ions.
3.Membrane Repolarization results from rapid sodium channel inactivation as well as a large
efflux of potassium ions resulting from activated potassium channels.
4.Hyperpolarization is a lowered membrane potential caused by the efflux of potassium ions and
closing of the potassium channels.
5.Resting state is when membrane potential returns to the resting voltage that occurred before the
stimulus occurred
3. Define Polarization, Depolarization and Repolarization of the cardiac cell.
-Polarization is the resting state of the myocardial wall when there is not electrical
activity in the heart and is recorded on the ECG strip as a flatline
-Depolarization is the loss of resting membrane potential due to the alteration of the
polarization of cell membrane
-Repolarization is the process of reaching the resting state before they can electrically
simulated again
4. Characteristics of cardiac muscle: Automaticity, Conductivity, Excitability, Contractility.
-Automaticity is an electrical function of the heart that gives it the ability of cardiac
pacemaker cells to spontaneously generate own electrical impulses without external
stimulation
-Excitability is an electrical function of the heart that allows the cardiac cells to respond
to electrical stimulus.
-Conductivity is an electrical function of the heart that allows cardiac cells to receive an
electrical stimulus and then to transmit the stimulus to other cardiac cells, so they
function collectively as a unit.
-Contractility is a mechanical function of the heart also referred to as rhythmicity. It gives
the heart the ability of cardiac cells to shorten and cause cardiac muscle contraction in
response to an electrical stimulus.
5. Explain the importance of a long Refractory period in cardiac muscle.
-The longer refractory period in the cardiac muscle cells prevents tetanus and results in a
relatively long relaxation period, during which the hearts chambers can refill with blood
Mean Arterial Blood Pressure
6. Define mean Arterial Blood pressure, Cardiac Output, and Peripheral Resistance
7. Explain the role of MAP in causing blood flow
MAP is the measurement that explains the average blood pressure in a person's blood
vessels during a single cardiac cycle. Mean arterial pressure is significant because it
measures the pressure necessary for adequate perfusion of the organs of the body.
Regulation of the Heart
8. Describe the Intrinsic regulation of the heart
9.
Relate the three types of extrinsic regulation of the heart and their effects.
The Heart and Homeostasis
10. Describe how changes in Blood Pressure, pH, carbon Dioxide, and Oxygen affect the
function of the heart
27.
11. Explain how extracellular ion concentration and body temperature affect the function of
the heart
CRITICAL
THINKING
 Explain How the Nervous system detects and responds to each of the
following:
a) A decrease in blood pressure:
a. The nervous system detects a decrease in blood pressure by
detecting the level of stretch on vascular walls and responds
by withdrawing vagal activity, increasing heart rate, and
increasing the activity of cardiac and vascular sympathetic
nerves.
b) an increase in blood carbon dioxide level
a. The chemoreceptors detect the levels of carbon dioxide in
the blood by monitoring the concentrations of hydrogen
ions in the blood. In response, the chemoreceptors detect
this change and send a signal to the medulla, which signals
the respiratory muscles to decrease the ventilation rate so
carbon dioxide levels and pH can return to normal levels.
c) decrease in blood pH
a. Chemoreceptors are receptors in the medulla and in the
aortic and carotid bodies of the blood vessels that detect
changes in blood pH and signal the medulla to correct those
changes. In response to a decease in blood pH, the
respiratory center, in the medulla, sends nervous impulses to
the external intercostal muscles and the diaphragm, to
increase the breathing rate and the volume of the lungs
during inhalation.
d) a decrease in blood oxygen levels
a. The nervous system uses cells in the carotid bodies to detect
a decrease in blood oxygen levels. In response, the carotid
bodies produce abundant hydrogen sulfide by cystathionineY-lyase, which activates nerve signals.
 Describe the Baroreceptor Reflex and the heart’s response to an
increase in venous return
Answer from class notes:
o Baroreceptors monitor blood pressure; in walls of internal
carotids and aorta. This sensory information goes to cardio
regulatory center in the medulla oblongata which can then
increase or decrease heart rate.
Answer from internet:
o The baroreceptor reflex is one of the body’s homeostatic
mechanisms that helps to maintain blood pressure at nearly
constant levels. It provides a rapid negative feedback loop in
which an elevated blood pressure causes the heart rate to
decrease. An increase in venous return of blood to the heart
will result in greater filling of the ventricles during diastole. So
the volume of blood in the ventricles at the end of diastole,
EDV, will be increased.
 What effect does an increase or a decrease in extracellular K, Ca, Na
ions have I the heart’s rate and force of the contractions?
Answer from class notes:
o Increase or decrease in extracellular K+ decreases heart rate.
o Heart block can result, which is the loss of AP conduction through the
heart.
Answer from internet:
o Elevated levels of extracellular potassium or sodium ions can
decrease heart rate and stroke volume. Abnormal potassium
levels interfere with the SA node, affecting heart rate. Too
much potassium causes cardiac contractions to become weak
and irregular, and too little potassium decreases the heart rate.
 How does temperature have on Herat Rate?
o Body temperature is an independent determinant of heart rate,
causing an increase of approximately 10 beats per minute per
degree centigrade.
 What is venous return? Explain how it affects preload. How does
preload affect cardiac output? State the Starling Law of the heart
o Venous return refers to the flow of blood from the periphery
back to the right atrium, and except for periods of a few
second, it is equal to cardiac output. When venous return to the
heart is increased, the end-diastolic pressure and volume of the
ventricles are increased, which stretches the sarcomeres,
thereby increasing their preload. Preload is related to cardiac
performance through the Frank-Starling law of the heart, a
decrease in preload diminishes the force of ventricular
contraction and therefore decreases stroke volume. As a result,
preload reduction generally results in a decreased in cardiac
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output. The Frank-Starling Law is the description of cardiac
hemodynamics as it relates to myocyte stretch and contractility,
The Frank-Starling Law states that the stroke volume of the left
ventricle will increase as the left ventricle volume increases
due to the myocyte stretch causing a more forceful systolic
contraction.
Define afterload, and describe its effects on the pumping
effectiveness of the heart
o Afterload is the pressure against which the heart must work to
eject blood during systolic pressure. The lower the afterload,
the more blood the heart will eject with each contraction.
What part of the Brain regulates the heart? Describe the ANS supply
to the heart
o The medulla. Heart rate is controlled by the two branches of
the autonomic nervous system. The sympathetic nervous
system and the parasympathetic nervous system. The
sympathetic nervous system releases the hormones to
accelerate the heart rate.
What effects do Parasympathetic and Sympathetic stimulation have
on the hear rate, force of contraction, and stroke volume?
o The sympathetic nervous system releases the hormones to
accelerate the heart rate. The parasympathetic nervous system
releases the hormone acetylcholine to slow the heart rate.
Neurotransmitter norepinephrine at shortens the repolarization
period, thus speeding the rate of depolarization and contraction,
which results in an increase in HR. In comparison,
parasympathetic stimulation releases ACh at the neuromuscular
junction from the vagus nerve. The membrane hyperpolarizes
and inhibits contraction to decrease the strength of contraction
and stroke volume, and to raise end-systolic volume.
Name the two main hormones that affect the heart. Where are they
produced, what cause they release, and what effects do they have on
the heart?
Answer from class notes:
o Epinephrine and norepinephrine from the adrenal medulla.
Occurs in response to increased physical activity, emotional
excitement, stress.
Review Questions (Samples)
1) The right side of the heart receives blood from the body and pumps through the ________
circulation to the lungs.
A) hepatic
B) pulmonary
C) peripheral
D) systemic
2) The delivery of oxygen and nutrients to the tissues of the body is accomplished through the
________ circulation.
A) hepatic
B) pulmonary
C) peripheral
D) systemic
3) The epicardium
A) covers the surface of the heart.
B) lines the walls of the ventricles.
C) is known as the fibrous pericardium.
D) attaches inferiorly to the diaphragm.
E) is also called endocardium.
4) Ezra is admitted to the cardiac unit with a diagnosis of endocarditis. When Ezra asks the nurse
where the infection is located, the nurse replies that the infection is in
A) the outer layer of the heart wall.
B) the inner lining of the heart.
C) a membranous sac that encloses the heart.
D) the muscular layer of the heart.
E) the lining of the mediastinum.
5) Which of the following terms is mismatched with its description?
A) Endocardium - covers the inner surfaces of the heart
B) Myocardium - cardiac muscle
C) Trabeculae carneae - found on the interior walls of ventricles
D) Pectinate muscles - muscles that close valves
E) Chordae tendineae - connective tissue strings that connect to cusps of valves
6) A stab wound into the heart can result in cardiac tamponade. This means that
A) blood enters the pleural cavity.
B) the heart is compressed by blood in the pericardial sac.
C) the electrical conduction system of the heart is damaged.
D) the left coronary artery has been damaged or cut.
E) the heart has lost all of its blood.
7) The function of the pericardial fluid is to
A) reduce friction between the pericardial membranes.
B) lubricate the heart valves.
C) replace any blood that is lost.
D) provide oxygen and nutrients to the endocardium.
E) stimulate the heart.
8) Blood vessels enter and exit from the ________ of the heart.
A) apex
B) base
C) auricles
D) trigone
E) inferior aspect
9) Blood in the pulmonary veins returns to the
A) right atrium.
B) left atrium.
C) right ventricle.
D) left ventricle.
E) coronary sinus.
10) Occlusion of which of the following would primarily damage the posterior wall of the heart?
A) Circumflex artery
B) Pulmonary artery
C) Right marginal artery
D) Coronary sinus artery
E) Right coronary artery
11) Blood flow through the coronary blood vessels decreases during myocardial contraction and
increases during myocardial relaxation.
TRUE
FALSE
12) Coronary artery disease can diminish myocardial blood flow resulting in the death of
myocardial cells. This condition is known as a myocardial ________.
A) attack
B) angina
C) necrosis
D) cirrhosis
E) infarction
13) The procedure whereby a small balloon is placed into a partially occluded coronary artery
and then inflated to increase blood flow through the artery is called a/an ________.
A) angioplasty
B) coronary bypass
C) urokinase injection
D) tissue plasminogen activation
E) angiogram
14) Angina pectoris is chest pain caused by reduced
A) stimulation of the myocardium.
B) blood supply to cardiac muscle.
C) fluid in the pericardial sac.
D) contractility of the heart.
E) action potentials from SA node.
15) Which of the following is NOT an enzyme given to someone experiencing a myocardial
infarction to break up blood clots?
A) Streptokinase
B) Tissue plasminogen activator (t-Pa)
C) Nitroglycerin
D) Urokinase
16) What is the foramen ovale?
A) An opening between the right and left atria in the embryo and fetus
B) An opening between the right and left ventricles in the embryo and fetus
C) An oval hole in the pericardium in the embryo and fetus
D) An opening between the pulmonary trunk and aorta in the embryo and fetus
17) The AV valve that is located on the same side of the heart as the origin of the aorta is the
A) bicuspid or mitral valve.
B) tricuspid valve.
C) aortic semilunar valve.
D) pulmonary semilunar valve.
E) coronary sinus valve.
18) Which blood vessel carries blood away from the left ventricle?
A) Aorta
B) Right atrium
C) Pulmonary trunk
D) Pulmonary arteries
E) Pulmonary veins
19) Which of the following heart chambers is correctly associated with the blood vessel that
enters or leaves it?
A) Right atrium – pulmonary veins
B) Left atrium – aorta
C) Right ventricle – pulmonary trunk
D) Left ventricle – superior vena cava and inferior vena cava
E) Right atrium – aorta
20) Action potentials pass from one cardiac muscle cell to another through areas of low electrical
resistance called
A) gap junctions.
B) fibrous heart rings.
C) electromagnetic discs.
D) sarcolemma sclerotic plaques.
E) tight junctions.
21) The "pacemaker" of the heart is the
A) right bundle branch.
B) left bundle branch.
C) AV node.
D) SA node.
E) PM node.
22) Which of the following sequences for the conducting system is correct?
A) AV node, AV bundle, SA node, Purkinje fibers, bundle branches
B) Purkinje fibers, bundle branches, AV node, AV bundle, SA node
C) SA node, AV node, AV bundle, bundle branches, Purkinje fibers
D) SA node, AV bundle, AV node, bundle branches, Purkinje fibers
E) AV node, SA node, bundle branches, AV bundle, Purkinje fibers
23) What is the importance of the delay in the action potential in the AV node?
A) It allows the action potential to reach both ventricles at the same time.
B) It allows an action potential to reach the left atrium so both atria contract together.
C) It allows an action potential to reach the left atrium so both atria contract together, before the
ventricles contract.
D) It allows time for the atria to fill with blood.
24) The spontaneous opening of Na+ channels marks the beginning of ________ of a cardiac
muscle cell.
A) depolarization
B) repolarization
C) hyperpolarization
D) isopolarization
E) afterpolarization
25) If the SA node is nonfunctional, which of the following is most likely to occur?
A) The heart will go into asystole (stop).
B) Tachycardia will develop.
C) Another portion of the heart will become the pacemaker.
D) The heart will go into defibrillation.
E) The heart will be desensitized.
26) Calcium channel blockers are frequently used to
A) increase the heart rate.
B) treat tachycardia or other arrhythmias.
C) speed up conduction of impulses through the AV node.
D) slow the closing of K+ channels.
E) treat bradycardia and low blood pressure.
27) The long refractory period observed in cardiac muscle
A) prolongs depolarization of the cardiac muscle.
B) prevents tetanic contractions of the cardiac muscle.
C) ensures that the heart has adequate time to contract.
D) prevents the heart rate from slowing down.
E) prevents an increase in heart rate.
28) The period of time in which cardiac muscle cells are insensitive to further stimulation is
called the
A) absolute refractory period.
B) hyperpolarization period.
C) AV period.
D) SA period.
E) ectopic focus.
29) The chamber of the heart that endures the highest pressure is the
A) right atrium.
B) left atrium.
C) right ventricle.
D) left ventricle.
E) coronary sinus.
30) Concerning heart sounds, which of the following is correct?
A) The first heart sound occurs at the beginning of ventricular systole.
B) The second heart sound is heard when the AV valves are closing.
C) The first heart sound is the sound of the semilunar valves closing.
D) The second heart sound occurs when blood flows into the superior vena cava.
E) The first heart sound occurs at the beginning of ventricular diastole.
31) Regurgitation of blood flow through the aortic semilunar valve would give rise to
A) the first heart sound.
B) the second heart sound.
C) a heart murmur.
D) an extra heartbeat.
E) end-systolic volume.
32) The volume of blood pumped during each cardiac cycle is the
A) stroke volume.
B) cardiac output.
C) cardiac reserve.
D) end-systolic volume.
E) end-diastolic volume.
33) The product of the stroke volume times the heart rate is known as the
A) end-diastolic volume.
B) end-systolic volume.
C) cardiac output.
D) cardiac reserve.
E) venous return.
34) End-diastolic volume minus end-systolic volume is equal to
A) cardiac output.
B) cardiac reserve.
C) pulse volume.
D) venous return.
E) stroke volume.
35) Mean arterial pressure is
A) cardiac output times peripheral resistance.
B) end-diastolic volume minus end-systolic volume.
C) maximum cardiac output minus cardiac output when at rest.
D) heart rate times stroke volume.
E) stroke volume times peripheral resistance.
36) Afterload is
A) the name given to an increase in end-diastolic volume.
B) the arterial pressure that the ventricles must overcome to eject blood.
C) the amount cardiac output must increase during exercise.
D) another name for venous return.
E) the extent to which ventricular walls are stretched.
37) Which of the following statements regarding intrinsic regulation of the heart is true?
A) Stretching the SA node will decrease generation of action potentials in the node.
B) Decreased venous return increases cardiac output.
C) The heart's pumping effectiveness is greatly influenced by small changes in afterload.
D) If cardiac muscle cells are slightly stretched, they have a stronger contraction force.
E) If cardiac muscle cells are slightly stretched, they have a weaker contraction force.
38) The relationship between preload and stroke volume is known as
A) extrinsic regulation.
B) cardiac reserve.
C) Starling Law of the heart.
D) minute volume.
39) Stimulation of the heart via the sympathetic nerves would
A) decrease heart rate.
B) decrease stroke volume.
C) increase the force of ventricular contraction.
D) increase end-systolic volume.
E) not affect heart rate and force of contraction.
40) Increased vagal stimulation would cause
A) the heart rate to decrease.
B) the heart rate to increase.
C) force of contraction to increase.
D) stroke volume to increase.
E) no change in heart rate, stroke volume, or force of contraction
41) Which of the following factors would cause an increase in heart rate?
A) Increased parasympathetic stimulation
B) Stimulation of baroreceptors in the aorta
C) Increased epinephrine release from the adrenal medulla
D) Increased production of atrial natriuretic factor
E) Stimulation through the vagus nerve
42) The baroreceptor reflex would cause which of the following events to occur if the reflex was
caused by an increase in blood pressure?
A) Increased parasympathetic stimulation of the heart
B) Increased heart rate
C) Increased cardiac output
D) Increased force of contraction
E) Increased sympathetic stimulation of the heart
43) Which of the following will increase the heart rate?
A) A rise in pH
B) An increase in the level of carbon dioxide in the blood
C) An increase in the level of blood oxygen
D) An increase in blood pressure
E) A decrease in the level of carbon dioxide in the blood
44) The cardio regulatory center of the brain is located in the
A) hypothalamus.
B) medulla oblongata.
C) cerebellum.
D) cerebrum.
E) diencephalons.
45) Chemoreceptors sensitive to blood carbon dioxide levels are primarily located in the
A) medulla oblongata.
B) carotid arteries.
C) right atrium.
D) left ventricle.
E) jugular veins.
46) Chemoreceptors sensitive to blood oxygen levels are primarily located in the
A) medulla oblongata.
B) carotid arteries.
C) right atrium.
D) left ventricle.
E) jugular veins.
47) Excess K+ in cardiac tissue causes
A) an increased heart rate.
B) a rapid repolarization of cardiac cells.
C) a decrease in the frequency of action potentials in the conduction system.
D) an increase in stroke volume.
E) an increase in the frequency of action potentials.
48) Aortic stenosis results from
A) a hole in the interatrial septum.
B) a weakening of heart muscle.
C) a narrowed opening through the aortic valve.
D) low oxygen levels.
E) leakage from the AV valves.
49) Fred was admitted to the cardiac unit with chest pains. No arrhythmias and no large changes
in the heart rate were observable. Blood samples taken over the next few days showed no
increase in enzymes, such as creatine phosphokinase. A possible treatment of the condition is
A) beta adrenergic blocking agents.
B) nitroglycerin.
C) calcium channel blocking agents.
D) aspirin.
E) exercise.
50) During hemorrhagic shock in which blood pressure is decreased, which of the regulatory
mechanisms is most important is increasing cardiac output to help maintain blood pressure?
A) Increased sympathetic stimulation of the heart
B) Increase venous return
C) Increase in parasympathetic stimulation of the heart
D) Increase vagal stimulation of the heart
E) Increase in the amplitude of the heart sounds
51) What must occur during exercise to ensure adequate oxygen delivery to cardiac muscle?
A) An increased oxygen release to cardiac muscle
B) A decreased oxygen content to skeletal muscle
C) Decreased heart rate
D) Increased coronary blood flow
52) Under resting conditions, the normal stroke volume is approximately ________.
A) 55 mL
B) 70 mL
C) 110 mL
D) 125 mL
E) 180 mL
53) The peripheral chemoreceptors that respond to oxygen levels of the blood and regulate heart
activity are located in
A) the left ventricle.
B) the infundibulum of the hypothalamus.
C) structures near the carotids and aortic arch.
D) the medulla oblongata.
E) the right ventricle.
54) Obstruction of the ________ will cause a more severe myocardial infarction (MI) than the
obstruction of any of the others.
A) left marginal vein
B) left coronary artery (LCA)
C) posterior interventricular vein
D) anterior interventricular branch
E) circumflex branch
55) A reduction in extracellular Ca2+ levels would lead to
A) increased force of cardiac muscle contraction due to increased interactions between actin and
myosin.
B) decreased force of cardiac muscle contraction due to a lack of release of Ca2+ from the
sarcoplasmic reticulum.
C) heart block due to depolarization of the sarcolemma.
D) heart block due to hyperpolarization of the sarcolemma.