Chapter 18 Homework
Look at ECGs
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How long is the cardiac cycle, assuming the heart beats 75 times per minute?
0.8 seconds
Increased pressure in the ventricles would close what valve(s)?
AV valves only
In a healthy individual which of the following would be low?
Afterload
Which portion of the electrocardiogram represents the depolarization wave received from the sinoatrial (SA) node through the atria?
P wave
During which portion of the electrocardiogram do the atria contract?
P-R interval
The order of impulse conduction in the heart, from beginning to end, is __________.
SA node, AV node, bundle of His, bundle branches, and Purkinje fibers
Which of the following is equivalent to the ventricular volume during isovolumetric contraction?
The end diastolic volume (EDV)
How would a decrease in blood volume affect both stroke volume and cardiac output?
decreased stroke volume and no change in cardiac output
Which of the following is equivalent to the ventricular volume during isovolumetric relaxation?
end systolic volume (ESV)
An abnormal P wave could be indicative of ______.
enlarged atria
The layers of the heart wall from superficial to deep are: __________.
epicardium, myocardium, and endocardium
Which of the following would increase heart rate?
epinephrine
Which of the following would increase heart rate?
epinephrine and norepinephrine
Which of the following increases stroke volume?
exercise
When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane?
fast calcium
Which of the following is the outermost covering of the heart?
fibrous pericardium
In what direction does blood flow through the heart?
from a region of high pressure to a region of low pressure
Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane?
gap junctions
What causes the aortic semilunar valve to close?
greater pressure in the aorta than in the left ventricle
Which of the following is NOT a factor that regulates stroke volume?
heart rate
What causes normal heart sounds?
heart valve closure
How would an increase in the sympathetic nervous system increase stroke volume?
increased contractility
By what mechanism would an increase in venous return increase stroke volume?
increased end diastolic volume
Which of the following would increase cardiac output to the greatest extent?
increased heart rate and increased stroke volume
Which of the following is NOT a vein that returns blood to the right atrium of the heart?
pulmonary vein
Which of the following does NOT deliver blood to the right atrium?
pulmonary veins
Consider the following characteristics of the cells found in muscle tissue. Which feature is shared by both cardiac muscle and skeletal muscle?
striations
The role of the coronary arteries is to __________.
supply blood to the heart tissue
In order to cause cardiac muscle contraction, the contractile cells must also depolarize. What causes the depolarization of the contractile cells?
the flow of positive ions from adjacent cells
What is the main function of heart valves?
to prevent backward flow of blood
The __________ valve is located between the right atrium and the right ventricle.
tricuspid
Which valve is located between the right atrium and ventricle?
tricuspid valve
The heart is actually (one, two, or three) pumps?
two pumps
The QRS complex represents __________.
ventricular depolarization
Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.
ventricular diastole
Most of the decrease in ventricular volume takes place during which phase of the cardiac cycle?
ventricular ejection
Ventricular pressure is greater than aortic pressure during which phase of the cardiac cycle?
ventricular ejection
Most of the increase in left ventricular volume takes place during what phase of the cardiac cycle?
ventricular filling
What does the T wave of the electrocardiogram (ECG) represent?
ventricular repolarization
At what point in the cardiac cycle is pressure in the ventricles the highest (around 120 mm Hg)?
ventricular systole
Repolarization of an autorhythmic cell is due to the opening of which channels?
voltage-gated potassium channels
At what point in the cardiac cycle does the AV valve open?
when atrial pressure becomes greater than ventricular pressure
At what point in the cardiac cycle does the semilunar valve close?
when pressure in the ventricle becomes less than aortic pressure
At what point in the cardiac cycle does the semilunar valve open?
when ventricular pressure becomes greater than aortic pressure
At what point during the cardiac cycle does the AV valve close?
when ventricular pressure becomes greater than atrial pressure
What is the source of ATP for cardiac muscle contraction?
cellular respiration
The first heart sound (the "lub" of the "lub-dup") is caused by __________.
closure of the atrioventricular valves
What is afterload?
back pressure exerted by arterial blood
The heart has __________ chambers and __________ valves.
4:4
At what rate does the sinoatrial (SA) node ensure depolarization in the heart?
75 beats of the heart per minute
Calculate the stroke volume if the end diastolic volume (EDV) is 135 mL/beat and the end systolic volume (ESV) is 60 mL/beat.
75 mL/beat
Which of the following is correct about the filling of the ventricles?
Most blood flows passively into the ventricles through open AV valves.
Which functional feature best describes the manner in which cardiac muscle contracts?
Automaticity (autorhythmicity) promotes the spontaneous contraction of the cardiac muscle cells.
Describe the pressures in the atria and ventricles that would cause the opening of the AV valves.
Pressure in the atria would be greater than the pressure in the ventricles.
Which portion of the electrocardiogram represents the time during which the atria repolarize?
QRS complex
Which of the following is true during ventricular systole?
The AV valves are closed.
Which of the following is NOT a difference between the left and right ventricles?
The left ventricle receives a smaller percentage of coronary blood supply than the right ventricle.
Isovolumetric relaxation is characterized by which of the following?
The semilunar and AV valves are closed.
During the ventricular ejection phase of the cardiac cycle, which of the following is true?
The semilunar valves are open.
When the atria contract, which of the following is true?
The ventricles are in diastole.
The left side of the heart is considered the systemic circuit pump.
True
Atrial pressure is greater than ventricular pressure during which phase of the cardiac cycle?
atrial contraction
Into what vessel does the left ventricle eject blood?
aorta
Which of the following cannot trigger tachycardia?
increased vagal tone
Which of the following would cause a decrease in the contractility of the heart?
increasing extracellular potassium levels
What is the period during the cardiac cycle when the ventricles are completely closed chambers and blood volume in the chambers remains constant as the ventricles contract?
isovolumetric contraction phase
Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.
isovolumetric contraction, ventricular ejection, isovolumetric relaxation
Into which chamber do the pulmonary veins send blood?
left atrium
Which chamber of the heart receives oxygenated blood via the pulmonary circuit?
left atrium
Which heart chamber receives blood from the pulmonary veins?
left atrium
Which chamber of the heart has the highest probability of being the site of a myocardial infarction?
left ventricle
Which chamber of the heart sends oxygenated blood to the aorta to the systemic circuit?
left ventricle
Which chamber pumps oxygenated blood out the aorta to the systemic circuit?
left ventricle
Which layer of the heart wall contracts and is composed primarily of cardiac muscle tissue?
myocardium
What separates the parietal and visceral pericardium?
pericardial cavity
One of the changes that occurs in the pacemaker potential (unstable resting membrane potential) in the SA node (an autorhythmic cell) is a decreased efflux of what ion?
potassium
The presence of an incompetent tricuspid valve would have the direct effect of causing ______.
reduced efficiency in the delivery of blood to the lungs
Into which chamber of the heart do the superior vena cava, inferior vena cava, and coronary sinus return deoxygenated blood?
right atrium
Which chamber receives blood from the superior and inferior vena cavae?
right atrium
Which heart chamber pumps unoxygenated blood out the pulmonary trunk?
right ventricle
Which heart chamber sends deoxygenated blood to the lungs?
right ventricle
Specifically, what part of the intrinsic conduction system stimulates the atrioventricular (AV) node to conduct impulses to the atrioventricular bundle?
sinoatrial (SA) node
Which of the following pacemaker cells generates impulses of approximately 75 depolarizations per minute in order to control the heart's contraction rate?
sinoatrial (SA) node
The heart's pacemaker is the __________.
sinoatrial node
