CH. 18 Heart
What is the expected heart rate when a heart is removed from a living body? the heart would immediately stop beating 50 beats / minute 75 beats / minute 100 beats / minute
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 ________. 170 ml / beat 50 ml / beat 70 ml / beat 120 ml / beat
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. 60 mL/beat 75 mL/beat 205 mL/beat 8100 mL/beat
75 mL/beat The SV is calculated by subtracting the ESV from the EDV. You are comparing the volume of the ventricle at its fullest to its emptiest.
Calculate the cardiac output if heart rate (HR) is 90 beats per minute, stroke volume (SV) is 110 ml/beatml/beat, end diastolic volume (EDV) is 140 mlml, and end systolic volume (ESV) is 30 mlml. 9.9 L/min 14.0 L/min 20.0 L/min 34.0 L/min
9.9 L/min Cardiac output is the product of heart rate times stroke volume. Cardiac output increases to meet increased metabolic demand, often by increasing both heart rate and stroke volume at the same time. This occurs, for example, during maximal exercise, when cardiac output may increase to four or five times the resting level.
Determine which ECG shows a normal sinus rhythm. A B C D
A All waves are clearly present in this ECG of a normal sinus rhythm
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. A high heart rate increases venous return, which increases end diastolic volume (EDV) and stroke volume (SV). A high heart rate decreases venous return, which increases end systolic volume (ESV) and stroke volume (SV). A low heart rate reduces the end diastolic volume (EDV) and stroke volume (SV), because an inadequate supply of blood is pumped into the ventricles.
A high heart rate reduces the end diastolic volume (EDV) and stroke volume (SV), because there is less time for ventricular filling. A slow heart rate allows more time for ventricular filling. Conversely, a faster heart rate allows less time. The amount the heart fills during diastole (EDV) has a direct impact on stroke volume.
Select the correct statement about cardiac output. A slow heart rate increases end diastolic volume, stroke volume, and force of contraction. If a semilunar valve were partially obstructed, the end systolic volume in the affected ventricle would be decreased. Stroke volume increases if end diastolic volume decreases. Decreased venous return will result in increased end diastolic volume.
A slow heart rate increases end diastolic volume, stroke volume, and force of contraction.
Which of these structures conduct(s) action potentials the slowest? Bundle branches Purkinje fibers AV bundle AV node
AV node Action potentials slow down as they pass through the AV node. This gives the atria time to finish contracting before the ventricles are depolarized.
Which of the following structures receives the depolarization wave from the atria and passes impulses onto the ventricles? AV node atrioventricular bundle bundle branches SA node
AV node The AV node receives the depolarizing wave from the atria and delays and coordinates that distribution to the ventricles.
Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles? SA node bundle branches Purkinje fibers AV node AV bundle (bundle of His)
AV node Yes, the AV node slows down the impulse giving the atria time to contract before the ventricles contract.
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 This is the correct order of stimulation of the heart muscle. The signal to the AV node would begin in the SA node.
Increased pressure in the ventricles would close what valve(s)? semilunar valves only AV valves only both semilunar and AV valves
AV valves only Yes, increased pressure in the ventricles would close the AV valves
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 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 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. This closed pressure system is important for the ventricles to be able to generate enough pressure to open the semilunar valves and eject blood from the heart.
Determine which of the following electrocardiogram (ECG) tracings is missing P waves but is otherwise regular. A B C D
B B illustrates a QRS complex and a T wave, but it is missing the P wave.
Which of the following graphs depict the cardiac cycle of an individual with chronic hypertension in which blood pressure is 140/90?
Chronic hypertension increases the work of the heart to pump blood and is linked to an increased risk of heart failure, vascular disease, renal failure, and stroke. Because chronic hypertension increases the risk of these serious problems without any symptoms that alert the patient to the elevated pressure, it is often referred to as a silent killer.
Which of the following can be heard with a stethoscope most easily? Closing of atrioventricular valves Blood flow into aorta Contraction of atria Isovolumetric contraction
Closing of atrioventricular valves Heart sounds are an extremely helpful diagnostic tool that is not invasive. The first heart sound, often described as a lubb, corresponds to the closing of the atrioventricular valves. The second heart sound is a sharper and crisper dupp that corresponds to the closing of the semilunar valves. Consequently, the two heart sounds mark the beginning and the end of ventricular systole.
An electrocardiogram (ECG) provides direct information about valve function. True 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 False
False
Increasing end-diastolic volume (EDV) and end-systolic volume (ESV) will increase stroke volume. True False
False Stroke volume (the volume of blood ejected from the ventricle during systole) is equal to the difference between EDV (the volume of blood in the ventricle before it contracts) and ESV (the volume of blood remaining in the ventricle after it contracts). Increasing EDV will result in a larger stroke volume; however, increasing ESV will result in a smaller stroke volume.
What is the effect of high blood pressure on cardiac output? High blood pressure increases afterload and reduces cardiac output (CO). High blood pressure increases preload and ventricular filling, thereby increasing cardiac output (CO). High blood pressure occurs only when the cardiac output is already very high. High blood pressure reduces afterload, thereby increasing cardiac output (CO).
High blood pressure increases afterload and reduces cardiac output (CO). High blood pressure does produce a resistant force to systolic contractions, thus increasing afterload and end systolic volume (ESV). If ESV increases, stroke volume decreases.
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. Yes, most of the ventricular filling is passive; atrial contraction adds just a little more blood.
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? QRS complex T wave S-T segment P wave
P wave The P wave represents the depolarization of the left and right atria and the beginning of atrial systole.
Contraction of the atria results from which wave of depolarization on the ECG tracing? T wave P wave QRS complex
P wave Yes, the P wave represents atrial depolarization, which leads to atrial contraction
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. Contractility would be increased, which would result in a larger cardiac output. Preload would be increased, which would result in a larger cardiac output.
Preload would be increased, which would result in a larger cardiac output. More blood returning to the heart would increase the volume of blood in the ventricles at the end of their filling phase (called end diastolic volume, or EDV). A larger EDV results in greater stretching of the myocardium, or a greater preload. Stretching (lengthening) the contractile cells brings them closer to their optimal length, allowing them to produce more force when stimulated to contract. The stronger contraction results in a larger stroke volume, and therefore 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. Pressure in the ventricles would be greater than in the atria. Pressures in the atria and ventricles would be equal.
Pressure in the atria would be greater than the pressure in the ventricles. Yes, higher pressure in the atria than in the ventricles forces the AV valves to open and blood moves into the ventricles.
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? Purkinje fibers initiate spontaneous action potentials, which cause the ventricles to contract early. Action potentials are not delayed sufficiently at the AV node. 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. 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. Action potentials normally originate in the SA node because the pacemaker cells there depolarize faster than pacemaker cells located elsewhere in the heart. However, certain drugs, such as caffeine, nicotine, or cocaine, can stimulate other pacemaker cells to speed up and temporarily "escape" the SA node rhythm. If this ectopic focus consists of Purkinje fibers, then ventricular contraction will occur prematurely, prior to ventricular filling. Without proper filling, this abnormal contraction pumps little blood and is not sensed. However, the following normal beat generated from the SA node has augmented filling and is sensed, resulting in the missed beat sensation.
Which portion of the electrocardiogram represents the time during which the ventricles are in systole? T wave QRS complex P wave Q-T interval
Q-T interval The Q-T interval is the period from the beginning of ventricular depolarization through ventricular repolarization, during which the ventricles are in systole.
Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat? AV bundle Internodal pathway AV node SA node
SA node Like the rest of the intrinsic conduction system, the SA node contains pacemaker cells that spontaneously depolarize. The cells within the SA node, however, depolarize faster than the other cells within the system. This causes action potentials to initiate in the SA node rather than in any of the other structures.
Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart? SA node AV bundle (bundle of His) AV node Purkinje fibers
SA node Yes, the SA Node spontaneously depolarizes, causing the wave of depolarization that spreads through the rest of the conduction system and heart.
Electrical impulses pass through the conduction system of the heart in the following sequence: SA node, bundle branches, AV node, bundle of His, and Purkinje fibers SA node, AV node, bundle of His, bundle branches, and Purkinje fibers SA node, bundle branches, bundle of His, AV node, and Purkinje fibers SA node, bundle of His, AV node, bundle branches, and Purkinje fibers
SA node, AV node, bundle of His, bundle branches, and Purkinje fibers The impulses of the heart originate at the SA node (pacemaker). The impulse is then transmitted to the AV node (atrioventricular node), where the impulse slows down to allow the atria to completely contract and thereby fill the adjacent ventricles. The AV node then transmits the impulse to the bundle of His, which branches into left and right bundle branches. The bundle branches give rise to the Purkinje fibers, which transmit the impulse to the ventricle walls and stimulate ventricular contraction.
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, increasing the heart rate. The SA node would depolarize more quickly, increasing the heart rate. The SA node would depolarize more quickly, decreasing the heart rate. There will be no change. The SA node would depolarize more slowly, reducing the heart rate.
The SA node would depolarize more slowly, reducing the heart rate. Diffusion of Na+ into the pacemaker cell causes a gradual depolarization of the cell membrane, called the pacemaker potential. If the rate of depolarization slows down, it will take longer for the membrane to reach threshold and trigger the next action potential, which will reduce heart rate.
Select the correct statement about the function of myocardial cells. The entire heart contracts as a unit or it does not contract at all. The refractory period in skeletal muscle is much longer than that in cardiac muscle. 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 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 sympathetic division continually stimulates the heart to keep it from slowing to an inadequate rate for oxygenating the body. 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 parasympathetic division normally inhibits the heart, keeping it beating at a slower rate than it would be on its own. The inhibitory signals from the vagus nerve inhibit the heart rate, thus keeping the heart rate lower than it would be if the vagus nerve were severed.
Which of the following descriptions of cardiac pacemaker cells is INCORRECT? The pacemaker cells of the sinoatrial (SA) node exhibit the fastest rate of spontaneous depolarization. Pacemaker cells do not have a stable resting membrane potential. The pacemaker cells of the atrioventricular (AV) node are smaller and have fewer gap junctions compared to the rest of the conduction system. Cutting the vagus nerve would allow the pacemaker cells of the sinoatrial (SA) node to generate action potentials at a faster rate. 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. The action potential begins with a slow depolarization towards threshold, called the pacemaker potential (or prepotential). At threshold (approximately -40 mV), Ca2+ channels open, allowing explosive entry of Ca2+ from the extracellular space. As a result, in pacemaker cells, it is the influx of Ca2+ (rather than Na+) that produces the rapid depolarization phase of the action potential.
Isovolumetric relaxation is characterized by which of the following? Blood flows backward through the heart from high to low pressure. The semilunar and AV valves are closed. Pressure in the atrium exceeds pressure in the ventricle. Pressure in the ventricle exceeds pressure in the aorta.
The semilunar and AV valves are closed. During isovolumetric relaxation, all valves into and out of the ventricles remain closed. This prevents blood from flowing backward through the heart.
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 False
True
The left side of the heart pumps the same volume of blood as the right. True False
True
When released in large quantities, thyroxine, a thyroid gland hormone, causes a sustained increase in heart rate. True False
True
Hemorrhage with a large loss of blood causes ________. no change in blood pressure but a slower heart rate. no change in blood pressure but a change in respiration. a rise in blood pressure due to change in cardiac output. a lowering of blood pressure due to change in cardiac output.
a lowering of blood pressure due to change in cardiac output
Atrial pressure is greater than ventricular pressure during which phase of the cardiac cycle? isovolumetric contraction ventricular ejection isovolumetric relaxation atrial contraction
atrial contraction Blood always flows from high to low pressure. During atrial contraction, blood flows from atria (high pressure) to ventricles (low pressure). Similarly, this same pressure gradient exists during ventricular filling.
The P wave on an electrocardiogram represents __________. ventricular depolarization atrial repolarization ventricular repolarization atrial depolarization
atrial depolarization The P wave reflects the depolarization of the atria.
During the isovolumetric relaxation phase of the cardiac cycle, _______. atrioventricular, aortic, and pulmonary valves are open atrioventricular valves are open; aortic and pulmonary valves are closed atrioventricular, aortic, and pulmonary valves are closed atrioventricular valves are closed; aortic and pulmonary valves are open
atrioventricular, aortic, and pulmonary valves are closed
What best describes afterload? cardiac reserve degree of stretch of the heart muscle. contractility of cardiac muscle. back pressure exerted by arterial blood.
back pressure exerted by arterial blood Afterload refers to the back pressure exerted by arterial blood, or the pressure that must be overcome for the ventricles to eject blood.
During the period of ventricular filling, ________. pressure in the heart is at its peak the atria remain in diastole blood flows mostly passively from the atria through the atrioventricular (AV) valves into the ventricles the aortic and pulmonary semilunar valves are open
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? aorta only pulmonary veins only pulmonary arteries only both the aorta and pulmonary trunk
both the aorta and pulmonary trunk
Norepinephrine acts on the heart by ________. decreasing heart contractility. blocking the action of calcium. causing a decrease in stroke volume. causing threshold to be reached more quickly
causing threshold to be reached more quickly.
The beginning of the QRS complex of the electrocardiogram (ECG) immediately precedes which of the following events? blood ejection from the ventricles atrial contraction closing of the atrioventricular valves closing of the semilunar valves
closing of the atrioventricular valves The QRS complex is a recording of ventricular depolarization. This depolarization begins just prior to the ventricular contraction it initiates. As the ventricles contract, the increase in ventricular pressure closes the atrioventricular valves, beginning isovolumetric contraction. As ventricular pressure increases above the corresponding blood vessel, only then do the semilunar valves open, initiating ventricular ejection.
The first heart sound (the "lub" of the "lub-dup") is caused by __________. closure of the semilunar valves ventricular contraction atrial contraction closure of the atrioventricular valves
closure of the atrioventricular valves The first heart sound (the "lub" of the "lub-dup") is generated by the closure of the atrioventricular valves.
An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________. end diastolic volume contractility heart rate end systolic volume
contractility Increased sympathetic activity increases heart contractility. This causes cardiac fibers to contract more forcefully at all levels of preload. Regardless of end diastolic volume, this mechanism increases stroke volume by reducing end systolic volume.
How would a decrease in blood volume affect both stroke volume and cardiac output? decreased stroke volume and decreased cardiac output. no change in stroke volume and decreased cardiac output. decreased stroke volume and no change in cardiac output. increased stroke volume and increased cardiac output
decreased stroke volume and no change in cardiac output Yes, a decreased blood volume would decrease the end diastolic volume, thus lowering the stroke volume. Although this would initially lead to a decrease in the cardiac output, heart rate would increase because of increased activity of the sympathetic nervous system in an effort to maintain cardiac output.
Which of the following would cause a DECREASE in cardiac output (CO)? heightened use of skeletal muscle. an increase in adrenal medulla output (epinephrine). suddenly standing up from a supine position. decreasing thyroid function (thyroxine)
decreasing thyroid function (thyroxine) Thyroxine increases basal metabolic rate, respiratory rate, and both heart rate and contractility.
What does the ECG wave tracing represent? contraction of the heart electrical activity in the heart
electrical activity in the heart Yes, the ECG waves show the depolarization and repolarization in various areas of the heart
An abnormal P wave could be indicative of ______. an abnormal AV node. an abnormal AV bundle. incomplete ventricular repolarization. enlarged atria
enlarged atria The P wave on an ECG tracing represents SA node firing and subsequent atrial depolarization.
Which of the following would increase cardiac output? parasympathetic stimulation decreased cytoplasmic calcium concentration during contraction epinephrine. high blood pressure
epinephrine Sympathetic stimulation leads to the release of epinephrine and norepinephrine, both of which increase heart rate and increase contractility, which increases stroke volume. Increasing heart rate and stroke volume increases cardiac output.
Which of the following would increase heart rate? epinephrine and norepinephrine increased activity of the parasympathetic nervous system acetylcholine decreased activity of the sympathetic nervous system
epinephrine and norepinephrine Yes, secreted by the adrenal medulla as a result of sympathetic stimulation, these hormones act as part of the sympathetic response, increasing heart rate.
Which of the following INCREASES stroke volume? exercise decrease in preload severe blood loss decrease in end diastolic volume (EDV)
exercise Exercise increases venous return, which would in turn increase the amount of blood in the presystolic ventricle (preload).
When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane? fast calcium fast sodium slow calcium potassium
fast calcium Yes, unlike nerve cells or cardiac muscle cells, fast calcium channels are responsible for the depolarization phase of the autorhythmic cell action potential. When the fast calcium channels open, calcium rushes into the cell making it less negative (or more positive).
In what direction does blood flow through the heart? from a region of high volume to a region of low volume from ventricles to atria from a region of high oxygen content to a region of low oxygen content from a region of high pressure to a region of low pressure
from a region of high pressure to a region of low pressure Blood moves through the heart from atria to ventricles and out large arteries, always from areas of high pressure to areas of lower pressure through one-way valves.
Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane? tight junctions gap junctions desmosomes intercalated discs
gap junction Yes, action potentials generated by the autorhythmic cells spread waves of depolarization to contractile cells through gap junctions. If the depolarization causes the contractile cells to reach threshold, they will in turn generate an action potential.
What causes the aortic semilunar valve to close? equal ventricular and aortic pressures greater pressure in the aorta than in the left ventricle higher ventricular pressure than aortic pressure
greater pressure in the aorta than in the left ventricle Yes, backflow of blood in the aorta (towards the left ventricle) closes the aortic semilunar valve
What causes heart sounds? opening of heart valves heart valve closure blood flowing from the atria into the ventricles. pressure of blood in the ventricles
heart valve closure Heart sounds are caused by heart valve closure.
Which of the following is an effect of epinephrine, norepinephrine, and thyroxine? increase end systolic volume decrease heart rate decrease cardiac output increase contractility
increase contractility Epinephrine, norepinephrine, and thyroxine secreted by the sympathetic nervous system directly increase contractility and heart rate, for the overall effect of increasing cardiac output. Likewise, end systolic volume would decrease with increased contractility.
How would an increase in the sympathetic nervous system increase stroke volume? decreased end diastolic volume increased end systolic volume increased end diastolic volume increased contractility
increased contractility Yes, an increase in sympathetic nervous system activity would increase contractility (by increasing available calcium), thus increasing stroke volume. Contractility causes an increase in stroke volume by decreasing end systolic volume; it does not change end diastolic volume.
By what mechanism would an increase in venous return increase stroke volume? increased end diastolic volume decreased end diastolic volume increased contractility increased end systolic volume
increased end diastolic volume Yes, an increase in venous return increases the end diastolic volume. The fibers are stretched more, resulting in an increase in the force of contraction (preload, or the Frank-Starling Mechanism).
Which of the following would increase cardiac output to the greatest extent? increased heart rate and decreased stroke volume. decreased heart rate and increased stroke volume. decreased heart rate and decreased stroke volume. increased heart rate and increased stroke volume
increased heart rate and increased stroke volume Yes, cardiac output = heart rate x stroke volume
Which of the following cannot trigger tachycardia? cardiovascular center. increased sympathetic stimulation. increased vagal tone. increased venous return
increased vagal tone The vagus nerve carries efferent parasympathetic motor impulses to the heart and other major organs. The SA node rate is slowed by impulses from the vagus nerve.
Which of the following would decrease stroke volume? increasing preload increasing sympathetic stimulation increasing contractility increasing afterload
increasing afterload Increasing afterload decreases stroke volume.
The plateau phase of an action potential in cardiac muscle cells is due to the ________. efflux of K+ through K+ channels influx of Ca2+ through slow Ca2+ channels. efflux of Ca2+ through fast Ca2+ channels. influx of Na+ through fast Na+ channels
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? ventricular filling isovolumetric relaxation phase ventricular ejection isovolumetric contraction phase
isovolumetric contraction phase The prefix -iso means "equal," so during any isovolumetric stage the volume does not change.
Put the phases of the cardiac cycle in the correct order, starting after ventricular filling. isovolumetric contraction, ventricular ejection, isovolumetric relaxation ventricular ejection, ventricular relaxation, isovolumetric contraction ventricular ejection, isovolumetric contraction, isovolumetric relaxation isovolumetric relaxation, ventricular ejection, isovolumetric contraction
isovolumetric contraction, ventricular ejection, isovolumetric relaxation Yes, the ventricles must contract and eject blood before they relax and fill again.
The second heart sound is heard during which phase of the cardiac cycle? isovolumetric relaxation isovolumetric contraction ventricular filling ventricular ejection
isovolumetric relaxation
Which heart chamber receives oxygenated blood from the lungs? right ventricle right atrium left atrium left ventricle
left atrium Oxygenated blood from the lungs returns to the left atrium of the heart
Which chambers of the heart contain oxygenated blood? right and left atria right atrium and ventricle left atrium and ventricle right and left ventricles
left atrium and ventricle
If the SA node is not functioning, an ECG will show ________. more P waves than QRS waves no QRS waves no P waves with a HR between 40-60 bpm higher P waves
no P waves with a HR between 40-60 bpm
Into which chamber of the heart do the superior vena cava, inferior vena cava, and coronary sinus return deoxygenated blood? right atrium left atrium right ventricle left ventricle
right atrium All of these vessels deliver blood to the right atrium.
As part of a blood drive on campus for the American Red Cross, you and your friends have just donated 500 ml 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 ml decrease in blood volume most likely affected your cardiac output, heart rate, and stroke volume? no change in cardiac output, decreased heart rate, increased stroke volume. no change in cardiac output, increased heart rate, decreased stroke volume. decrease in cardiac output, decreased heart rate, decreased stroke volume. increase in cardiac output, increased heart rate, increased stroke volume.
no change in cardiac output, increased heart rate, decreased stroke volume Donating blood does not alter resting cardiac output. However, the decreased blood volume does decrease venous return and end diastolic volume. This decreases preload, thereby lowering stroke volume. By itself, decreased stroke volume would decrease cardiac output. But remember, the body still requires a resting blood flow of around 5 L/minL/min. To meet this demand, homeostatic mechanisms quickly restore cardiac output to resting levels. For example, heart rate is increased as parasympathetic influence is removed and sympathetic activity is increased. Even though your blood volume is a bit low, your body has no problem compensating to meet your resting metabolic needs. Running away from a tiger? Now that might be a different story.
During which of these stages are the aortic and pulmonary valves open? phase 1 phase 2a phase 2b phase 3
phase 2b During phase 2b, the pressure in the ventricles exceeds that of the aorta and pulmonary trunk, so their valves open and allow blood to be ejected.
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 sodium calcium
potassium Yes, if there is a decreased efflux of potassium while there is a normal influx of sodium, the inside of the cell would become less negative. Thus, threshold would be reached. The ability of these autorhythmic cells to spontaneously depolarize is what results in the pacemaker potential.
Exercise results in skeletal muscles compressing veins which encourages blood to return to the heart. In this scenario, which of the following is correct? venous return decreases stroke volume decreases preload increases end diastolic volume (EDV) decreases
preload increases
Hypercalcemia could cause ______. increased osteoclast activity. prolonged T wave. hypersecretion of parathyroid hormone. All of the listed responses are correct.
prolonged T wave The T wave on an ECG tracing represents ventricular repolarization. Repolarization requires the net efflux of K+ ions. Recall that changes in normal concentrations of ions (like Ca2+) in the plasma can affect the ability of other ions to move in and out of the cell.
Which vessel(s) of the heart receive(s) blood from the right ventricle? pulmonary trunk pulmonary veins venae cavae aorta
pulmonary trunk
Which of the following does NOT deliver deoxygenated blood to the heart? pulmonary veins inferior vena cava superior vena cava coronary sinus
pulmonary veins The pulmonary veins deliver oxygenated blood to the left atrium
Which of the following terms is correctly matched to its description? ventricular diastole: period of ventricular contraction quiescent period: period of total heart relaxation atrial systole: period of atrial relaxation stroke volume: amount of blood pumped out by each ventricle in one minute
quiescent period: period of total heart relaxation During each cardiac cycle there is a period of time in which both the atria and ventricles are relaxed (in diastole) at the same time; this is called the quiescent period.
The presence of an incompetent tricuspid valve would have the direct effect of causing ______. reduced efficiency in the delivery of blood to the lungs reduced efficiency in the delivery of blood to the myocardium reduced efficiency in the delivery of blood from the lungs to the heart reduced efficiency in the delivery of blood from the head to the heart
reduced efficiency in the delivery of blood to the lungs The tricuspid valve separates the right atrium and the right ventricle. It must remain tightly closed during ventricular contraction so blood can be pumped out of the ventricle and into the pulmonary arteries.
Isovolumetric contraction ________. occurs immediately after the aortic and pulmonary semilunar valves close occurs only in people with heart valve defects refers to the short period during ventricular systole when the ventricles are completely closed chamber soccurs while the atrioventricular (AV) valves are open
refers to the short period during ventricular systole when the ventricles are completely closed chamber
To auscultate the aortic semilunar valve, you would place your stethoscope in the ________. second intercostal space to the left of the sternum second intercostal space to the right of the sternum fifth intercostal space inferior to the left nipple fifth right intercostal space
second intercostal space to the right of the sternum
Specifically, what part of the intrinsic conduction system stimulates the atrioventricular (AV) node to conduct impulses to the atrioventricular bundle? subendocardial conducting network (Purkinje fibers) interventricular septum sinoatrial (SA) node bundle branches
sinoatrial (SA) node The sinoatrial node, by spontaneously depolarizing faster than the atrioventricular node, initiates heart contraction.
In order to cause cardiac muscle contraction, the contractile cells must also depolarize. What causes the depolarization of the contractile cells? an unstable resting membrane potential in the contractile cells. the flow of negative ions from adjacent cells. the flow of positive ions from adjacent cells
the flow of positive ions from adjacent cells Yes, the flow of positive ions from the autorhythmic cells (or adjacent cells) brings the membrane to threshold initiating depolarization of the contractile cell.
If the vagal nerves to the heart were cut, the result would be that ________. parasympathetic stimulation would increase, causing a decrease in heart rate the atrioventricular (AV) node would become the pacemaker of the heart the heart rate would increase by about 25 beats per minute the heart would stop, since the vagal nerves trigger the heart to contract
the heart rate would increase by about 25 beats per minute
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 T wave would decrease the S-T segment 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? fibrosis of cardiac muscle. thinning of the valve flaps. decline in cardiac reserve atherosclerosis
thinning of the valve flaps
What does the QRS wave of the electrocardiogram (ECG) represent? ventricular repolarization ventricular depolarization atrial repolarization atrial depolarizaton
ventricular depolarization Ventricular depolarization is represented by the QRS complex of an ECG
What does the QRS complex represent in the ECG wave tracing? ventricular depolarization atrial repolarization ventricular repolarization atrial depolarization
ventricular depolarization Yes, the QRS complex represents depolarization in the ventricles, which have greater mass than the atria.
Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________. ventricular diastole ventricular systole
ventricular diastole Yes, both occur during ventricular diastole when the ventricles are not actively contracting and ejecting blood.
Ventricular pressure is greater than aortic pressure during which phase of the cardiac cycle? ventricular ejection isovolumetric contraction isovolumetric relaxation ventricular filling
ventricular ejection While pressure in the ventricle is greater than pressure in the aorta, the semilunar valve remains open. This allows blood to be ejected from the ventricle.
At what point in the cardiac cycle is pressure in the ventricles the highest (around 120 mm Hg in the left ventricle)? mid-to-late diastole (atrial contraction) early diastole (isovolumetric relaxation) ventricular filling ventricular systole
ventricular systole Left ventricular systole typically produces maximum pressures of around 120 mm Hg
Repolarization of an autorhythmic cell is due to the opening of which channels? chemically gated calcium channels voltage-gated potassium channels Chemically gated potassium channels. voltage-gated sodium channels
voltage-gated potassium channels Yes, opening of voltage-gated potassium channels causes positive potassium ions to move out of the cell. This efflux of potassium causes the cell to become more negative inside thus, repolarizing the cell
At what point in the cardiac cycle does the AV valve open? when ventricular pressure becomes greater than aortic pressure when aortic pressure becomes greater than ventricular pressure when atrial pressure becomes greater than ventricular pressure when the semilunar valve closes
when atrial pressure becomes greater than ventricular pressure Blood flows through the heart in one direction (atria-ventricles-large arteries) and from high to low pressure. When pressure in the atrium becomes greater than ventricular pressure, the AV valve opens; and blood flows from the atrium into the ventricle.
At what point in the cardiac cycle does the semilunar valve close? when ventricular pressure becomes greater than atrial pressure when atrial pressure becomes greater than ventricular pressure when ventricular pressure becomes greater than aortic pressure when pressure in the ventricle becomes less than aortic pressure
when pressure in the ventricle becomes less than aortic pressure When pressure in the ventricle drops below aortic pressure, the semilunar valve shuts. This prevents blood from flowing backward through the heart.
The atrioventricular (AV) valves are closed ________. when the ventricles are in diastole. when the ventricles are in systole. while the atria are contracting. by the movement of blood from atria to ventricles
when the ventricles are in systole
At what point in the cardiac cycle does the semilunar valve open? when atrial pressure becomes greater than ventricular pressure when the AV valve closes when ventricular pressure becomes greater than atrial pressure when ventricular pressure becomes greater than aortic pressure
when ventricular pressure becomes greater than aortic pressure When pressure in the ventricle exceeds pressure in the aorta, the semilunar valve opens. This allows blood to be ejected from the ventricle.
At what point during the cardiac cycle does the AV valve close? when the semilunar valve opens when aortic pressure becomes greater than ventricular pressure when ventricular pressure becomes greater than atrial pressure when ventricular pressure becomes greater than aortic pressure
when ventricular pressure becomes greater than atrial pressure. When ventricular pressure rises above atrial pressure, the AV valve closes. This prevents blood from flowing backward through the heart.