A&P 2 Exam Review: Chapter 17
What is a contractile cell with a membrane potential of 0 mV experiencing?
Plateau Phase
During what part of the action potential will calcium ions enter the contractile cell?
Plateau phase During the plateau phase of the action potential, calcium ions enter the contractile cell. Depolarization is sustained at about 0 mV during the action potential of a contractile cell, which is known as the plateau phase. This critically important phase is mostly the result of the slow opening of calcium ion channels and the resulting influx of calcium ions. As the calcium ions enter, potassium ions continue to leave, so there is little net change in membrane potential. The calcium ion channels are also slow to close, which allows the plateau phase to last much longer than the initial depolarization phase. Note that these are the same types of calcium ion channels as those in pacemaker cells, but they simply play a different role in the cell's action potential.
The degree of stretch experienced by the sarcomeres in the ventricle cells before they contract is called __________.
Preload
What is the function of the valves in the heart?
Prevent backflow of blood through the heart
Which vessel is guarded by a semilunar valve at its base?
Pulmonary Trunk
Which of the following blood vessels is not a great blood vessel of the heart?
Pulmonary arteries
Oxygenated blood is delivered to the left atrium through the ____________.
Pulmonary veins
Which electrocardiogram (ECG) finding can be used to measure heart rate?
R-R interval The R-R interval can be used to measure heart rate. The R-R interval is the time between two successive R waves. This interval represents the entire duration of the generation and spread of an action potential through the heart and can be measured to determine the heart rate. The P-R interval is the period from the beginning of the P wave to the beginning of the QRS complex. The P-R interval represents the time it takes for the depolarization from the sinoatrial (SA) node to spread through the atria to the ventricles; it includes the atrioventricular (AV) node delay. The Q-T interval is the time from the beginning of the QRS complex to the end of the T wave. During the Q-T interval, the ventricular cells are undergoing action potentials. Between the end of the S wave and the beginning of the T wave is the S-T segment. The S-T segment is flat because it is recorded during the plateau phase of the ventricles, and no net changes occur in electrical activity. Elevation or depression of the S-T segment is seen with many clinical conditions, most notably myocardial ischemia and myocardial injury and infarction.
What is initiated by a rapid influx of sodium ions into contractile cells creating a positive membrane potential inside the cell?
Rapid depolarization phase The rapid influx of sodium ions into contractile cells creates a positive membrane potential inside the cell and initiates the rapid depolarization phase. The pacemaker cell action potentials cause voltage changes in adjacent cells, which activate voltage-gated sodium ion channels in the sarcolemma. This causes an immediate and massive influx of sodium ions, which rapidly depolarizes the membrane. This upstroke is much faster than that of a pacemaker cell depolarization because calcium ion channels activate more slowly than do sodium ion channels.
What valve prevents the backflow of blood from the right ventricle into the right atrium?
Right atrioventricular valve (tricuspid valve)
What normally serves as the pacemaker of the entire heart?
Sinoatrial (SA) node
What is the volume of blood pumped out by one ventricle per heart beat?
Stroke volume (SV)
What two values are needed to calculate cardiac output (CO) for a ventricle?
Stroke volume (SV) and heart rate (HR)
Which if the following ECG tracing components represents ventricular repolarization?
T wave
What part of an electrocardiogram (ECG) represents ventricular repolarization?
T wave The small T wave occurs after the S wave of the QRS complex and represents ventricular repolarization. The T wave is an upward deflection under normal conditions. However, certain pathological states, such as myocardial ischemia, may cause the T waves to become inverted as a result of functional changes in the cells' electrical activity. The large QRS complex, which represents ventricular depolarization, is actually three separate waves. The Q wave is the first downward deflection, the R is the large upward deflection, and the S is the second downward deflection. The small, initial P wave represents the depolarization of all cells within the atria except the sinoatrial (SA) node. The P wave nearly always registers as an upward deflection on the ECG. The S-T segment is flat because it is recorded during the plateau phase of the ventricles, and no net changes occur in electrical activity.
What obscures atrial repolarization on an electrocardiogram (ECG)?
The QRS complex obscures atrial repolarization on an electrocardiogram (ECG). Atrial repolarization occurs as the ventricles depolarize. This repolarization does produce a small electrical signal, but it is generally obscured by the much larger QRS complex and therefore not visible on the tracing. The large QRS complex, which represents ventricular depolarization, is actually three separate waves. The Q wave is the first downward deflection, the R is the large upward deflection, and the S is the second downward deflection.
Choose the correct statement. The right side of the heart pumps blood into the aorta, systemic arteries, and arterioles None of the choices are correct The left side of the heart pumps blood to the pulmonary circuit The right atrium receives deoxygenated blood from the venous circulation Oxygenated blood returns to the right atrium from the lungs
The right atrium receives deoxygenated blood from the venous circulation
What activity is occurring in the heart during the Q-T interval on an electrocardiogram (ECG)?
The ventricular cells are undergoing action potentials.
Arteries always conduct blood away from the heart, while veins conduct blood towards the heart. T/F
True
Because the output of one blood flow circuit becomes the input of the other, the two sides of the heart contract simultaneously and eject the same volume of blood. T/F
True
The aortic valve closes when the pressure in the aorta exceeds the pressure in the left ventricle. T/F
True
The heart chambers must be filled before contracting, so correct timing (atria followed by ventricles) is critical for efficient pumping. T/F
True
The second heart sound (S2) occurs at the beginning of ventricular diastole, when the semilunar valves close. T/F
True
The serous pericardium is divided into an outer parietal layer and an inner visceral layer, which is adhered to the surface of the heart. T/F
True
Which cranial nerves have a negative chronotropic effect on heart rate?
Vagus nerves (CN X)
Both the left and right atria receive blood from ________.
Veins
Which of the following cardiac dysrhythmias is immediately life-threatening and manifests on the electrocardiogram (ECG) with chaotic activity?
Ventricular fibrillation Ventricular fibrillation is immediately life-threatening and manifests on the electrocardiogram (ECG) with chaotic activity. It is treated with defibrillation, or an electric shock to the heart. The shock depolarizes all ventricular muscle cells simultaneously and throws the cells into their refractory periods. Ideally, the sinoatrial (SA) node will resume pacing the heart after the shock is delivered. In fibrillation, the electrical activity in the heart essentially goes haywire, causing parts of the heart to depolarize and contract while others are repolarizing and not contracting.
In comparison to skeletal muscle fibers, the contractile fibers of the heart are depolarized for __________ period of time.
a longer
The P wave on an electrocardiogram (ECG) represents the depolarization of cells in the __________.
atria
Inotropic agents affect __________.
contractility The endocrine system releases a variety of chronotropic and inotropic agents, including epinephrine, norepinephrine, thyroid hormone, and glucagon. The sympathetic nervous system innervates the heart and releases epinephrine and norepinephrine, which are positive inotropic agents.
The right side of the heart receives ________.
deoxygenated blood from the systemic circuit
The visceral pericardium is the same as the ________.
epicardium
High-pressured blood in the ventricles ________.
forces the semilunar valves open At the beginning of the ventricular ejection phase, the pressure in the ventricles rises to a level higher than that in the pulmonary trunk and aorta, and this pushes the semilunar valves open.
What surface groove separates the right and left ventricles?
interventricular sulcus
The correct order of blood flow, starting with venous blood entering the heart
right atrium, right ventricle, pulmonary trunk and arteries, pulmonary capillaries, pulmonary veins, left atrium, left ventricle, aorta and systemic arteries
The right and left atria depolarize and contract following the arrival of the action potential from the __________.
sinoatrial (SA) node The right and left atria depolarize and contract following the arrival of the action potential from the sinoatrial (SA) node. The SA node is the normal pacemaker of the entire heart; electrical rhythms generated and maintained by the SA node are known as sinus rhythms. The SA node generates an action potential, which spreads rapidly via gap junctions to the surrounding atrial cells. The impulses are then conducted by specialized atrial conducting fibers to the atrioventricular (AV) node. The AV node and Purkinje fiber system normally only conduct action potentials generated by the SA node. After the AV node delay, the action potential is conducted to the AV bundle and then to the right and left bundle branches. The action potential is then conducted from the AV bundle to the right and left bundle branches. At this point, depolarization spreads along the Purkinje fibers system to the contractile cardiac muscle cells of the ventricles. The terminal branches penetrate the ventricles and finally come into contact with the contractile cardiac muscle cells.
The depolarization phase of a myocardial contractile cell occurs as a result of ___________ ion influx.
sodium
Blood in the right atrium should travel next past the ________.
tricuspid valve and into the right ventricle
Blood from the systemic circuit returns to the heart via the
venae cavae
the cardiac cycle correct order, beginning with passive ventricular filling
ventricles fill to70-80%, atrial systole, ventricles fill with last 20-30%, ventricular systole/atrial diastole/av valves close, isovolumetric contraction, semilunar valves open, ventricular ejection, ventricular diastole/semilunar valves, isovolumetric relaxation, av valves open
Calculate the end-systolic volume (ESV) if the end-diastolic volume (EDV) in a resting heart is 110 ml and stroke volume (SV) is 70 ml.
40 ml
Approximately how much blood is pumped from each ventricle during the ventricular ejection phase?
70 ml
What percentage of atria blood flows passively into the ventricles?
80% The atrioventricular valves are open because of the higher atrial pressure, and blood flows down its pressure gradient from the atria into the ventricles. Nearly 80% of the total blood volume of the atria drains passively in this manner into the ventricles. At the beginning of the ventricular filling phase, the atria are in diastole, but as blood continues to drain into the ventricles, the pressure gradient becomes smaller and filling slows. At this point, atrial systole takes place and the contracting atria eject a variable volume of blood into the ventricles—as much as the remaining 20% of blood volume or as little as just a few percent.
According to the Frank-Starling law, a bigger preload will result in __________.
A stronger contraction
Which of the following terms refers to the force the ventricles must overcome to eject blood into their respective arteries? A: Afterload B: Preload C: Contractility D: Stroke volume
A: Afterload
Which of the following events is not part of the cardiac cycle? A: Atrial contraction phase B: Ventricular filling phase C: Isovolumetric relaxation phase D: Isovolumetric contraction phase
A: Atrial contraction phase We can divide the cardiac cycle into four main phases defined by the actions of the ventricles and the positions of the valves: filling, contraction, ejection, and relaxation. These four phases are as follows: ventricular filling phase, isovolumetric contraction phase, ventricular ejection phase, and isovolumetric relaxation phase.
Which of the following cell populations does not spontaneously generate action potentials in the cardiac conduction system? A: Contractile cells B: Purkinje fibers C: Atrioventricular node D: Sinoatrial node
A: Contractile cells are not a type of pacemaker cells that spontaneously generate action potentials in the cardiac conduction system. Contractile cells make up the great majority (99%) of cardiac muscle cells. Pacemaker cells rhythmically and spontaneously generate action potentials that trigger the other type of cardiac muscle cell, known as contractile cells, to also have action potentials.
Which of the following statements describes the total refractory period of cardiac muscle? A: It is longer than the total refractory period for skeletal muscle. B: It is shorter than the total refractory period for skeletal muscle. C: It is about the same as the total refractory period for skeletal muscle. D: It is longer than the contraction of cardiac muscle.
A: It is longer than the total refractory period for skeletal muscle. The total refractory period of cardiac muscle is longer than the total refractory period for skeletal muscle. A refractory period is the time during which an excitable cell cannot be stimulated to contract again (see Chapter 10). The effective refractory period is functionally the same as the absolute refractory period in skeletal muscle fibers, although the absolute refractory period is a result of a different mechanism (sodium ion channel inactivation). The absolute refractory periods of skeletal muscles fibers are so short that tetanus can occur with repeated stimulation. However, the effective refractory period in cardiac muscle cells is so long that the cells cannot enter a state of tetany. This allows the heart to relax and the ventricles to refill with blood before the cardiac muscle cells are stimulated to contract again.
Which of the following is not a risk factor for coronary artery disease or myocardial ischemia? A: Low blood pressure B: Smoking C: Older than age 50 for females D: Male gender
A: Low Blood Pressure
Which wave on the electrocardiogram (ECG) corresponds with the ventricular filling phase of the cardiac cycle? A: P wave B: S wave C: T wave D: S-T segment
A: P wave During the ventricular filling phase, the sinoatrial (SA) node fires an action potential, which is propagated through the atria and delayed at the atrioventricular (AV) node.
Which of the following structures is associated with the atria? A: Pectinate muscles B: Papillary muscle C: Trabeculae carnea D: Chordae tendineae
A: Pectinate muscles
Which of the following vessels carries oxygenated blood? A: Pulmonary vein B: Superior vena cava C: Pulmonary artery D: Pulmonary trunk
A: Pulmonary vein
Which of the following pacemaker cell populations has the slowest intrinsic rate of depolarization at about 20 times per minute? A: Purkinje fiber system B: Atrioventricular (AV) node C: Sinoatrial (SA) node D: Atrioventricular (AV) bundle
A: Purkinje fiber system its cells depolarize only about 20 times per minute. The cells of this system are sometimes called atypical pacemakers because their action potentials rely on different ion channels and they function in a slightly different way.
Which of the following statements best describes how coronary artery anastomoses might help a patient with coronary artery disease? A: They provide alternate routes of blood flow when a vessel is blocked. B: They increase the volume of blood that enters the right atrium. C: They allow the lungs to pick up more oxygen in the pulmonary circuit. D: They prevent atrioventricular (AV) valve cusps from everting.
A: They provide alternate routes of blood flow when a vessel is blocked.
Which of the following vessels carries oxygenated blood? A: pulmonary vein B: pulmonary artery C: superior vena cava D: pulmonary trunk
A: pulmonary vein
Where does the left ventricle send blood?
Aorta
What blood vessels do ventricles always pump blood into?
Arteries
Which hormone decreases cardiac output by decreasing blood volume and preload?
Atrial natriuretic peptide The heart (specifically the atria) acts as an endocrine organ and produces a hormone called atrial natriuretic peptide (ANP). ANP lowers blood pressure by decreasing sodium ion retention in the kidneys, therefore reducing osmotic water reabsorption and the volume and pressure of blood in the blood vessels.
What allows the atria and ventricles to depolarize and contract separately?
Atrioventricular (AV) node delay
Which of the following factors would increase cardiac output to the greatest extent? A: Increased heart rate and decreased stroke volume B: Increased heart rate and increased stroke volume C: Decreased heart rate and increased stroke volume D: Decreased heart rate and decreased stroke volume
B: Increased heart rate and increased stroke volume To determine cardiac output for a ventricle, we need to know both its stroke volume and heart rate. Stroke volume can be easily calculated by subtracting the amount of blood in the ventricle at the end of a contraction (the end-systolic volume, or ESV) from the amount of blood in the ventricle after it has filled during diastole (end-diastolic volume, or EDV). In an average heart, the resting stroke volume is equal to about 70 ml. To find the cardiac output, you simply multiply the heart rate by the stroke volume.
Which of the following statements best describes the apex of the heart? A: Superior tip of the heart and points toward the left side B: Inferior tip of the heart and points toward the left side C: Inferior tip of the heart and points toward the right side D: Superior tip of the heart and points toward the right side
B: Inferior tip of the heart and points toward the left side
Which of the following paths does an action potential in the heart normally take? A: AV bundle AV node where it is delayed right and left bundle branches Purkinje fibers ventricular contractile cells SA node atrial contractile cells B: SA node atrial contractile cells AV node where it is delayed AV bundle right and left bundle branches Purkinje fibers ventricular contractile cells C: Purkinje fibers ventricular contractile cells SA node atrial contractile cells AV bundle AV node where it is delayed right and left bundle branches D: SA node AV bundleright and left bundle branches atrial contractile cells AV node where it is delayed Purkinje fibers ventricular contractile cells
B: SA node atrial contractile cells AV node where it is delayed AV bundle right and left bundle branches Purkinje fibers ventricular contractile cells
Which of the following is NOT a vessel entering the right atrium? A: inferior vena cave B: pulmonary vein C: superior vena cava D: coronary sinus
B: pulmonary vein
The mitral valve is the clinical name for the ______________.
Bicuspid Valve
What might happen if the papillary muscles and/or chordae tendineae stopped functioning?
Blood would leak back into the atria from the ventricles.
What cardiac dysrhythmia does a patient have with a resting heart rate of 50 beats per minute?
Bradycardia
Which of the following hormones decrease cardiac output by decreasing blood volume and preload? A: Norepinephrine B: Aldosterone C: Atrial natriuretic peptide D: Antidiuretic hormone
C: Atrial natriuretic peptide
Which of the following ion channels are time-gated closing channels? A: Potassium ion channels B: Voltage-gated sodium ion channels C: Calcium ion channels D: Chloride ion channels
C: Calcium ion channels Calcium ion channels are present in all cardiac muscle cells. These channels exhibit voltage-gated opening but time-gated closing, meaning that they close after a certain period regardless of the voltage.
Which of the following events can be heard most easily with a stethoscope? A: Closing of semilunar valves B: Contraction of atria C: Closing of atrioventricular valves D: Contraction of the ventricles
C: Closing of atrioventricular valves
Which of the following blood vessels are associated with the coronary sinus? A: Marginal B: Circumflex C: Great Cardiac D: Posterior interventricular
C: Great Cardiac
The rapid depolarization phase of cardiac pacemaker cells occurs because of the influx of ____________ ions
Calcium
Autorhythmicity in the heart is a function of ________.
Cardiac Pacemaker Cells
What condition results from excess fluid in the pericardial cavity compressing the heart and reducing the capacity of the ventricles to fill with blood?
Cardiac tamponade
What structure attaches the cusps of the atrioventricular valves to the papillary muscles?
Chordae tendineae
Which coronary artery supplies the left atrium and parts of the left ventricle?
Circumflex artery
Which of the following chemical messengers decreases heart rate? A: Glucagon B: Norepinephrine C: Epinephrine D: Acetylcholine
D: Acetylcholine The parasympathetic nervous system innervates the heart by the left and right vagus nerves (CN X). Both of these nerves release acetylcholine when stimulated. Acetylcholine primarily affects the sinoatrial (SA) node, decreasing its rate of action potential generation. This negative chronotropic effect slows the heart rate and can even stop the heart temporarily if the parasympathetic stimulation is strong enough.
Which of the following cell populations does not spontaneously generate action potentials in the cardiac conduction system? A: Purkinje fibers B: Atrioventricular node C: Sinoatrial node D: Contractile cells
D: Contractile cells Contractile cells are not a type of pacemaker cells that spontaneously generate action potentials in the cardiac conduction system. Contractile cells make up the great majority (99%) of cardiac muscle cells. Pacemaker cells rhythmically and spontaneously generate action potentials that trigger the other type of cardiac muscle cell, known as contractile cells, to also have action potentials.
Which of the following is true? A: The ventricles begin contracting at the base, and the contraction spreads towards the apex, squeezing blood through the great vessels. B: The connective tissue of the heart isolates the right and left atria from each other C: The conduction delay that occurs at the AV node allows the ventricles to complete their contraction prior to atrial contraction D: The intristic rate of depolarization of the SA node can be modified by the autonomic nervous system
D: The intristic rate of depolarization of the SA node can be modified by the autonomic nervous system
Which of the following functions is not associated with the heart? A: To help maintain homeostasis of blood pressure B: To produce a hormone called atrial natriuretic peptide C: To pump blood through two different sets of vessels, or circuits D: To increase the rate at which erythrocytes are formed
D: To increase the rate at which erythrocytes are formed
Cardiac muscle cells A: are not branching B: are not striated C: are connected to each other via tight junctions D: are multinucleate E: none of the choices are true
E: none of the choices are true
What provides a graphic representation of all the action potentials occurring in the heart?
Electrocardiogram
What largely determines preload?
End-diastolic volume (EDV)
What are the three layers of the heart wall from superficial to deep?
Epicardium, myocardium, and endocardium
Blood or any other liquid, flows from an area of low pressure to an area of high pressure. T/F
False
Parasympathetic innervation has a positive inotropic effect and therefore decreases the heart rate, while sympathetic innervation has a negative inotropic effect and therefore increases heart rate. T/F
False
The atrioventricular valves open to allow blood to flow from the ventricles into the atria. T/F
False
The right ventricle has a thicker wall than the left ventricle, because of its heavier work load. T/F
False
What is the most superficial layer of the pericardial sac?
Fibrous Pericardium
Which opening in the interatrial septum of the fetal heart connects the right and left atrium?
Foramen ovale
The purpose of the serous fluid within the pericardial cavity is to decrease ____________ as the heart moves
Friction
What kind of ion channels are unique to pacemaker cells?
HCN channels. A pacemaker cell action potential oscillates—that is, it never remains at a resting level and instead occurs in a cycle, with the last event triggering the first. This is possible because of the HCN channels, which are nonspecific cation channels that are unique to pacemaker cells.
Looking in a microscope, what are the visible structures that join cardiac muscle cells?
Intercalated Disks
During what phase is the S1 heart sound first heard?
Isovolumetric contraction phase
Heart tissue dies during a myocardial infarction (MI), and a person's survival and recovery depend on the extent of cell death and the chamber(s) involved. In which chamber would the loss of function be most damaging to survival?
Left Ventricle
Which chamber generates the highest pressure during systole?
Left Ventricle
Which cardiac chamber has the thickest wall?
Left ventricle
The pulmonary circuit involves blood flow from the heart to the:
Lungs
The left atrioventricular valve is also know as the _______ valve.
Mitral/Bicuspid
What percentage of the total number of cardiac muscle cells are pacemaker cells?
Only about 1% of the total number of cardiac muscle cells. There are three populations of these cells in the heart that are capable of spontaneously generating action potentials and setting the pace of the heart. The cardiac conduction system includes the following three populations of pacemaker cells: sinoatrial node, atrioventricular node, and Purkinje fibers. Contractile cells make up the great majority (99%) of cardiac muscle cells.
A damaged atrioventricular (AV) bundle or AV node will primarily affect the length of the __________.
P-R interval
