Ch. 18 Heart
What is the effect of high blood pressure on cardiac output?
High blood pressure increases afterload and reduces cardiac output (CO).
The beginning of the QRS complex of the electrocardiogram (ECG) immediately precedes which of the following events?
closing of the atrioventricular valves
The first heart sound (the "lub" of the "lub-dup") is caused by __________.
closure of the atrioventricular valves
An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.
contractility
Atrial pressure is greater than ventricular pressure during which phase of the cardiac cycle?
atrial contraction
The P wave on an electrocardiogram represents __________.
atrial depolarization
During the isovolumetric relaxation phase of the cardiac cycle, _______.
atrioventricular, aortic, and pulmonary valves are closed
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 would cause a DECREASE in cardiac output (CO)? -suddenly standing up from a supine position -heightened use of skeletal muscle -decreasing thyroid function (thyroxine) -an increase in adrenal medulla output (epinephrine)
decreasing thyroid function (thyroxine)
What does the ECG wave tracing represent?
electrical activity of the heart
An abnormal P wave could be indicative of ______.
enlarged atria
Which of the following would increase cardiac output? -decreased cytoplasmic calcium concentration during contraction -high blood pressure -epinephrine -parasympathetic stimulation
epinephrine
Which of the following would increase heart rate? -epinephrine and norepinephrine -decreased activity of the sympathetic nervous system -acetylcholine -increased activity of the parasympathetic nervous system
epinephrine and norepinephrine
Which of the following is an effect of epinephrine, norepinephrine, and thyroxine? -decrease cardiac output -increase contractility -decrease heart rate -increase end systolic volume
increase contractility
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? -decreased heart rate and decreased stroke volume -decreased heart rate and increased stroke volume -increased heart rate and decreased stroke volume -increased heart rate and increased stroke volume
increased heart rate and increased stroke volume
Which of the following cannot trigger tachycardia? -cardiovascular center -increased sympathetic stimulation -increased vagal tone -increased venous return
increased vagal tone
Total peripheral resistance ______. -increases as blood vessel diameter increases -is not a major factor in blood pressure in healthy individuals -increases as blood viscosity increases -decreases with the increasing length of the blood vessel
increases as blood viscosity increases
Which of the following would decrease stroke volume? -increasing afterload -increasing sympathetic stimulation -increasing preload -increasing contractility
increasing afterload
The plateau phase of an action potential in cardiac muscle cells is due to the ________.
influx of Ca2+ through slow Ca2+ channels
What is the period during the cardiac cycle when the valves leading to and from the ventricles are completely closed and blood volume in the ventricles remains constant as the walls 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
The second heart sound is heard during which phase of the cardiac cycle?
isovolumetric relaxation
Which chambers of the heart contain oxygenated blood?
left atrium and ventricle
Which of the following terms is correctly matched to its description? -ventricular diastole: period of ventricular contraction -atrial systole: period of atrial relaxation -quiescent period: period of total heart relaxation -stroke volume: amount of blood pumped out by each ventricle in one minute
quiescent period: period of total heart relaxation
The presence of an incompetent tricuspid valve would have the direct effect of causing ______.
reduced efficiency in the delivery of blood to the lungs
Isovolumetric contraction ________.
refers to the short period during ventricular systole when the ventricles are completely closed chambers
Hypercalcemia could cause ______.
prolonged T wave
Which vessel(s) of the heart receive(s) blood from the right ventricle?
pulmonary trunk
Which of the following does NOT deliver deoxygenated blood to the heart? -superior vena cava -pulmonary veins -inferior vena cava -coronary sinus
pulmonary veins
Into which chamber of the heart do the superior vena cava, inferior vena cava, and coronary sinus return deoxygenated blood?
right atrium
To auscultate the aortic semilunar valve, you would place your stethoscope in the ________.
second intercostal space to the right of the sternum
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
If the vagal nerves to the heart were cut, the result would be that ________.
the heart rate would increase by about 25 beats per minute
At what point in the cardiac cycle is pressure in the ventricles the highest (around 120 mm Hg in the left ventricle)?
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
What is the expected heart rate when a heart is removed from a living body?
100 beats/minute
Given an end diastolic volume (EDV) of 120 ml / beat and an end systolic volume (ESV) of 50 ml / beat, the stroke volume (SV) would be ________.
70 ml/beat
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
How does heart rate affect stroke volume?
A high heart rate reduces the end diastolic volume (EDV) and stroke volume (SV), because there is less time for ventricular filling.
Electrical link(s) between atria and ventricles
AV bundle
Delay(s) occurs here while atria contract
AV node
Which of the following structures receives the depolarization wave from the atria and passes impulses onto the ventricles?
AV node
Increased pressure in the ventricles would close what valve(s)?
AV valves only
Convey(s) the impulse down the interventricular septum
Bundle branches
The volume of blood per minute pumped out by one ventricle
Cardiac output (CO)
The number of heart beats per minute
Heart rate (HR)
Link(s) between the SA node and AV node
Internodal pathways
Set(s) the pace for the entire heart
SA node
Isovolumetric relaxation is characterized by which of the following?
The semilunar and AV valves are closed.
Which heart chamber receives oxygenated blood from the lungs?
left atrium
The atrioventricular (AV) valves are closed ________.
when the ventricles are in systole
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
Calculate the cardiac output if heart rate (HR) is 90 beats per minute, stroke volume (SV) is 110 ml/beat, end diastolic volume (EDV) is 140 ml, and end systolic volume (ESV) is 30 ml.
9.9 L/min
Select the correct statement about cardiac output. -A slow heart rate increases end diastolic volume, stroke volume, and force of contraction. -Stroke volume increases if end diastolic volume decreases. -Decreased venous return will result in increased end diastolic volume. -If a semilunar valve were partially obstructed, the end systolic volume in the affected ventricle would be decreased.
A slow heart rate increases end diastolic volume, stroke volume, and force of contraction.
Which of these structures conduct(s) action potentials the slowest? -Purkinje fibers -AV bundle -AV node -Bundle branches
AV node
Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles?
AV node
Trace the pathway of stimulation through the heart. Which of these pathways shows stimulation in the correct order? -subendocardial conducting network, interventricular septum, AV bundle, AV node -AV bundle, subendocardial conducting network, interventricular septum, SA node -SA node, interventricular septum, AV node, papillary muscles -AV node, AV bundle, interventricular septum, subendocardial conducting network
AV node, AV bundle, interventricular septum, subendocardial conducting network
Which best describe the isovolumetric contraction phase of the cardiac cycle? -The pressure from the atrial contractions opens the semilunar valves. -As ventricular systole starts, the AV valves close, which immediately opens the semilunar valves. -As pressure builds up in the ventricles during systole, the AV valves open and allow blood to leave the heart. -As ventricular systole starts, the AV valves are closed and the semilunar valves are closed. Because the ventricles are contracting and both valves are closed, pressure increases rapidly leading to ejection.
As ventricular systole starts, the AV valves are closed and the semilunar valves are closed. Because the ventricles are contracting and both valves are closed, pressure increases rapidly leading to ejection.
Which of the following can be heard with a stethoscope most easily?
Closing of atrioventricular valves
The volume of blood in one ventricle before contraction
End diastolic volume (EDV)
The volume of blood in one ventricle after contraction
End systolic volume (ESV)
An electrocardiogram (ECG) provides direct information about valve function. True or False
False
Increasing end-diastolic volume (EDV) and end-systolic volume (ESV) will increase stroke volume. True or False?
False
The "lub" sounds of the heart are valuable in diagnosis because they provide information about the function of the heart's pulmonary and aortic semilunar valves. True or False?
False
When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane?
Fast calcium
Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane?
Gap junctions
Which of the following is correct about the filling of the ventricles? -The majority of ventricular filling is caused by contraction of the atria. -Most blood flows passively into the ventricles through open AV valves.
Most blood flows passively into the ventricles through open AV valves.
Contraction of the atria results from which wave of depolarization on the ECG tracing?
P wave
Which portion of the electrocardiogram represents the wave-like change in charge in the positive direction received by the atria from the sinoatrial (SA) node?
P wave
Electrical impulses pass through the conduction system of the heart in the following sequence:
SA node, AV node, bundle of His, bundle branches, and Purkinje fibers
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
As your skeletal muscles contract during physical activity, more blood is returned to the heart. Which variable would be affected and what would be the outcome of this action? -End-systolic volume would be increased, which would increase cardiac output. -Afterload would increase, which would increase cardiac output. -Preload would be increased, which would result in a larger cardiac output. -Contractility would be increased, which would result in a larger cardiac output.
Preload would be increased, which would result in a larger cardiac output.
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.
Convey(s) the impulse throughout the ventricular walls
Purkinje fibers
A person notices his or her heart beat because he or she senses blood being pumped by the heart. Excessive caffeine intake can lead to irregular heart rhythms (arrhythmias) that patients perceive as "skipped beats." Given that caffeine is a stimulant, which of the following mechanisms best explains the reason for the feeling that the heart skipped a beat? -Action potentials are not delayed sufficiently at the AV node. -Action potentials propagate into the ventricles before the contractile cells have repolarized from the previous heartbeat. -Purkinje fibers initiate spontaneous action potentials, which cause the ventricles to contract early. -Spontaneous action potentials in the SA node overlap such that the repolarizing phase of one action potential cancels out the depolarizing phase of the next.
Purkinje fibers initiate spontaneous action potentials, which cause the ventricles to contract early.
Which portion of the electrocardiogram represents the time during which the ventricles are in systole?
Q-T interval
Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?
SA node
The volume of blood per heart beat pumped out by one ventricle
Stroke volume (SV)
What would happen to the SA node if a chemical blocker was used to reduce transport of Na+ into the pacemaker cells?
The SA node would depolarize more slowly, reducing the heart rate.
Select the correct statement about the function of myocardial cells. -The influx of potassium ions from extracellular sources is the initiating event in cardiac muscle contraction. -Cardiac muscle cells are innervated by sympathetic, parasympathetic, and somatic nerve fibers so that the nervous system can increase heart rate. -The refractory period in skeletal muscle is much longer than that in cardiac muscle. -The entire heart contracts as a unit or it does not contract at all.
The entire heart contracts as a unit or it does not contract at all.
Which statement best describes the autonomic nervous system's role in regulating heart rate? -The parasympathetic division does not innervate the heart at all, and the sympathetic division innervates it only slightly. -The parasympathetic division increases the heart rate during strenuous exercise or conditions of fright or anxiety. -The parasympathetic division normally inhibits the heart, keeping it beating at a slower rate than it would be on its own. -The sympathetic division continually stimulates the heart to keep it from slowing to an inadequate rate for oxygenating the body.
The parasympathetic division normally inhibits the heart, keeping it beating at a slower rate than it would be on its own.
Which of the following descriptions of cardiac pacemaker cells is INCORRECT? -Cutting the vagus nerve would allow the pacemaker cells of the sinoatrial (SA) node to generate action potentials at a faster rate. -Pacemaker cells do not have a stable resting membrane potential. -The pacemaker cells of the sinoatrial (SA) node exhibit the fastest rate of spontaneous depolarization. -The pacemaker cells of the atrioventricular (AV) node are smaller and have fewer gap junctions compared to the rest of the conduction system. -The rapid depolarization phase of the pacemaker cell action potential is due to Na+ influx through Na+ channels.
The rapid depolarization phase of the pacemaker cell action potential is due to Na+ influx through Na+ channels.
If blood volume decreased dramatically due to massive bleeding, the autonomic nervous system will attempt to maintain cardiac output by increasing the heart rate. True or False?
True
The left side of the heart pumps the same volume of blood as the right. True or False
True
When released in large quantities, thyroxine, a thyroid gland hormone, causes a sustained increase in heart rate. True or False?
True
The volume of blood per minute flowing into one atrium
Venous return (VR)
Hemorrhage with a large loss of blood causes ________.
a lowering of blood pressure due to change in cardiac output
What best describes afterload?
back pressure exerted by arterial blood
During the period of ventricular filling, ________.
blood flows mostly passively from the atria through the atrioventricular (AV) valves into the ventricles
Which of the following receive(s) blood during ventricular systole?
both the aorta and pulmonary trunk
Norepinephrine acts on the heart by ________.
causing threshold to be reached more quickly
In what direction does blood flow through the heart?
from a region of high pressure to a region of low pressure
What causes the aortic semilunar valve to close?
greater pressure in the aorta than in the left ventricle
What causes heart sounds?
heart valve closure
If the SA node is not functioning, an ECG will show ________.
no P waves with a HR between 40-60 bpm
As part of a blood drive on campus for the American Red Cross, you and your friends have just donated 500 mlml of blood. You are now relaxing at the student lounge, waiting for A&P lab to begin. Unfortunately, even though you are thirsty, you haven't bothered to buy yourself a drink. Other than a little soreness of the skin and tissue around your median cubital vein, you feel fine. How has your 500 mlml decrease in blood volume most likely affected your cardiac output, heart rate, and stroke volume?
no change in cardiac output, increased heart rate, decreased stroke volume
Exercise results in skeletal muscles compressing veins which encourages blood to return to the heart. In this scenario, which of the following is correct? -stroke volume decreases -preload increases -end diastolic volume (EDV) decreases -venous return decreases
preload increases
Specifically, what part of the intrinsic conduction system stimulates the atrioventricular (AV) node to conduct impulses to the atrioventricular bundle?
sinoatrial (SA) node
During exercise, which of the following would occur on an electrocardiogram (ECG) compared to an individual at rest? -the P-R interval would decrease -the S-T segment would decrease -the T wave would decrease -the time from one R to the R of the next heartbeat would decrease
the time from one R to the R of the next heartbeat would decrease
Which of the following is NOT an age-related change affecting the heart? -decline in cardiac reserve -atherosclerosis -fibrosis of cardiac muscle -thinning of the valve flaps
thinning of the valve flaps
What does the QRS complex represent in the ECG wave tracing?
ventricular depolarization
What does the QRS wave of the electrocardiogram (ECG) represent?
ventricular depolarization
Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.
ventricular diastole
Ventricular pressure is greater than aortic pressure during which phase of the cardiac cycle?
ventricular ejection