Chapter 20 The Heart
By blocking calcium channels, verapamil will decrease the force of cardiac contraction, which directly lowers Karen's stroke volume.
Karen is taking the medicine verapamil, a drug that blocks the calcium channels in cardiac muscle cells. What effect should this medication have on Karen's stroke volume?
the available filling time becomes shorter as the heart rate increases
Cardiac output cannot increase indefinitely because? A. the available filling time becomes shorter as the heart rate increases B. the cardiovascular centers adjust the heart rate C. the rate of spontaneous depolarization decreases D. the ion concentrations of pacemaker plasma membranes decrease
produce of heart rate and stroke volume
Cardiac output is equal to the? A. difference between the end-diastolic volume and the end-systolic volume B. product of heart rate and stroke volume C. difference between the stroke volume at rest and the stroke volume during exercise D. stroke volume less the end-systolic volume E. produce of heart rate and blood pressure
The SA node, is the pacemaker of the heart.
Describe the function of the SA node in the cardiac cycle?
relaxes and fills with blood
During diastole, a chamber of the heart? A. relaxes and fills with blood B. contracts and pushes blood into an adjacent chamber C. experiences a sharp increase in pressure D. reaches a pressure of approximately 120mm Hg
stroke volume
During the cardiac cycle, the amount of blood ejected from the left ventricle when the semilunar valve opens is the? A. stroke volume B. end-diastolic volume C. end-systolic volume D. cardiac output
The left AV valve is probably regurgitating. When an AV valve fails to close properly, blood flowing back into the atrium produces a murmur. A murmur at the beginning of systole implicates the left AV valve because this is the period when the valve has just closed and the blood in the ventricle is under increasing pressure; thus the likelihood of backflow is the greatest.
Harvey has a heart murmur in his left ventricle that produces a loud "gurgling" sound at the beginning of systole. Which valve is probably faulty?
The SA node, which is composed of cells that exhibit rapid prepotential, is the pacemaker of the heart. The AV node slows the impulse that signals contraction, because its cells are smaller than those of the conduction pathway.
How does the SA node function differ from that of the AV node?
CO (in mL/min) = HR (in beats/min) X SV (in mL/beat)
How is cardiac output calculated?
the AV valves will not close properly
If the papillary muscles fail to contract? A. the ventricles will not pump blood B. the atria will not pump blood C. the semilunar valves will not open D. the AV valves will not close properly E. none of these happen
auscultation
Listening to the heart sounds is termed?
the cardiac centers of the medulla
The autonomic centers for cardiac function are located in? A. the myocardial tissue of the heart B. the cardiac centers of the medulla C. the cerebral cortex D. all of these structures
It physically isolates the muscle fibers of the atria from those of the ventricles and It maintains the normal shape of the heart
The cardiac skeleton of the heart has which two of the following functions? A. It physically isolates the muscle fibers of the atria from those of the ventricles B. It maintains the normal shape of the heart C. It helps distribute the forces of cardiac contraction D. It allows more rapid contraction of the ventricles E. It strengthens and helps prevent overexpansion of the heart
contractile cells do not normally exhibit automaticity
The cells of the conducting system differ from the contractile cells of the heart in that? A. conducting cells are larger and contain more myofibrils B. contractile cells exhibit prepotentials C. contactile cells do not normally exhibit automaticity D. both A and B are correct
Person 1 has a CO of 4500 mL, and person 2 has a CO of 8550 mL. According to the Frank-Startling principal, in a normal heart the CO is directly proportional to the venous return. Thus, person 2 has the greater venous return. Ventricular filling decreases with increases heart rate; person 1 has the lower heart rate and therefore the longer ventricular filling time.
The following measurements were made on two individuals (the values recorded remained stable for one hour) Person 1: heart rate 75 bpm; stroke volume 60 mL Person 2 heart rate 90 bpm; stroke volume 95 mL Which person has the greatest venous return? Which person has the longer ventricular filling time?
right atrium
The great cardiac vein drains blood from the heart muscle to the? A. left ventricle B. right ventricle C. right atrium D. left atrium
mediastinum
The heart is surrounded by the? A. pleural cavity B. peritoneal cavity C. abdominopelvic cavity D. mediastinum E. abdominal cavity
visceral pericardium
The serous membrane covering the outer surface of the heart is the? A. endocardium B. myocardium C. parietal pericardium D. visceral pericardium
endocardium
The simple squamous epithelium covering the heart valves is the? A. epicardium B. endocardium C. myocardium D. cardiac skeleton
epicardium
The visceral pericardium, which covers the outer surface of the heart?
SA node; AV node; AV bundle; right and left bundle branches; Purkinje fibers (into the mass of ventricular muscle tissue)
Trace the normal pathway of an electrical impulse through the conducting system of the heart?
During tachycardia, there is less time between contractions for the heart to fill with blood again. Thus, over time the heart fills with less and less blood, and pumps less blood out. As the stroke volume decreases, the cardiac output decreases to the point where not enough blood reaches the brain, loss of consciousness occurs.
Vern is suffering form cardiac arrhythmias and is brought into the emergency room of a hospital. In the emergency room he begins to exhibit tachycardia and as a result loses consciousness. Explain why Vern lost consciousness?
The pulmonary and aortic semilunar valves.
What 2 valves prevent the backflow of blood from the pulmonary trunk and aorta into the right and left ventricles.
The right atrioventricular (AV) valve (the tricuspid valve) and the left atrioventricular (AV) valve (the bicuspid valve)
What 2 valves prevent the backflow of blood from the ventricles into the atria?
1. preload 2. contractibility 3. afterload
What 3 factors regulate stroke volume to ensure that the left and right ventricles pump equal volume of blood?
1. The right atrioventricular (AV) valve (the tricuspid valve) 2. The left atrioventricular (AV) valve (the bicuspid valve) 3. The pulmonary semilunar valve 4. The aortic semilunar valve
What are the 4 valves in the heart?
1. epicardium 2. myocardium 3. endocardium
What are the three distinct layers of that make up the heart wall?
parasympathetic activation
What decreases the heart rate and the force of contraction?
stroke volume and heart rate
What factors influence cardiac output?
epinephrine, norepinephrine, glucagon, and thyroid hormones
What hormones have positive inotropic effects, which means that they increase the strength of cardiac contraction?
sympathetic activation
What increases the heart rate and the force of contraction?
endocardium
What is a squamous epithelium that covers the inner surfaces of the heart, including the valves?
Cardiac Output (CO)
What is the amount of blood pumped by the left ventricle in one minute?
The cardiac cycle comprises the events in a complete heartbeat, including a contraction/relaxation period for both atria and ventricles.
What is the cardiac cycle?
contractibility
What is the forcefulness of contraction of individual ventricular muscle fibers called?
myocardium
What is the muscular wall of the heart, which forms both atria and ventricles? It contains cardiac muscle tissue and associated connective tissues, blood vessels, and nerves.
afterload
What is the pressure that must be exceeded before blood can be ejected from the ventricles called?
The first sound, (lubb), which marks the start of ventricular contraction, is produced as the AV valves close and the semilunar valves open
What is the source and significance of the first heart sound?
The fourth heart sound is associated with atrial contraction.
What is the source and significance of the fourth heart sound?
The second sound, (dupp), occurs when the semilunar valves close and the AV valves open, marking the start of ventricular diastole.
What is the source and significance of the second heart sound?
The third heart sound is associated with blood flow into the ventricles
What is the source and significance of the third heart sound?
preload
What is the stretch on the heart before it contracts called?
Stroke volume (SV)
What is the volume of blood ejected by a ventricle in a single contraction?
The cycle begins with atrial systole as the atria contract and push blood into the relaxed ventricles. As the atria relax (atrial diastole), the ventricles contract (ventricular systole), forcing blood through the semilunar valves into the pulmonary trunk and aorta. The ventricles then relax (ventricular diastole). For the rest of the cardiac cycle, both the atria and ventricles are in diastole; passive filling occurs.
What phases and events are necessary to complete a cardiac cycle?
During ventricular contraction, tension in the papillary muscles pulls against the chordae tendineae, which keep the cusps of the AV valve from swinging into the atrium. This action prevents backflow, or regurgitation, of blood into the atrium as the ventricle contracts.
What role do the chordae tendineae and papillary muscles play in the normal function of the AV valves?
the refractory period of cardiac muscle
Which of the following is larger? A. the refractory period of cardiac muscle B. the refractory period of skeletal muscle
