If the SA node is damaged, which part of the heart is most likely to take over as a pacemaker?
|A)||atrial myocardial cells|
|B)||AV nodal cells|
|D)||ventricular myocardial cells|
The normal rate of spontaneous depolarization of the AV node is
|A)||20 - 40 per minute|
|B)||40 - 60 per minute|
|C)||70 - 80 per minute|
|D)||over 100 per minute|
In which choice are the components of the heart placed in correct order of decreasing intrinsic rhythm?
|A)||SA node, AV node, Purkinje cells|
|B)||SA node, Purkinje cells, AV node|
|C)||AV node, SA node, Purkinje cells|
|D)||Purkinje cells, AV node, SA node|
The cardiac pacemaker potential is caused by cyclic changes in membrane potential that occur in which of the following sequences?
|A)||slow inflow of Na+ ; rapid K+ inflow; slow K+ outflow|
|B)||slow inflow of Ca2+ ; rapid Na+ inflow; rapid K+ outflow|
|C)||slow inflow of K+ without Na+ outflow; rapid Na+ inflow; rapid K+ outflow|
|D)||slow inflow of Na+ without K+ outflow; rapid Ca2+ inflow; rapid K+ outflow|
The plateau phase of the cardiac myocardial cell potential
|A)||normally keeps the heart from beating faster than 70 - 80 times per minute|
|B)||allows the cell to depolarize spontaneously instead of having to be stimulated by nerve fibers|
|C)||prevents tetanus, which would cease pumping action of the heart|
|D)||allows the myocardial cells time to rest during the contraction|
What do skeletal muscle cells, cardiac autorhythmic cells, and cardiac contractile cells have in common?
|A)||In all three, depolarization to threshold is caused primarily by K+ outflow|
|B)||In all three, depolarization between threshold and peak membrane potential is caused entirely by Na+ inflow|
|C)||In all three, repolarization is caused by K+ outflow|
|D)||In all three, the depolarization phase is longer than the repolarization phase|
If lines were drawn on a typical ECG recording showing where atrial and ventricular systole begin and end, then the ventricular systole would be seen as beginning during a ____ and ending during the next ____.
|A)||P wave; QRS complex|
|B)||PR segment; T wave|
|C)||QRS complex; T wave|
|D)||T wave; P wave|
The semilunar valves close at the beginning of
Which part of the cardiac cycle occurs between the time the AV valves close and the semilunar valves open?
|C)||isovolumetric phase of ventricular systole|
|D)||ejection phase of ventricular systole|
The action of acetylcholine after binding to muscarinic receptors on the SA node is to
|A)||open K+ channels, causing hyperpolarization and a decreased rate of spontaneous depolarization|
|B)||close K+ channels, causing depolarization and and increased rate of spontaneous depolarization|
|C)||open Ca2+ channels, causing increased Ca2+ entry and a stronger contraction|
|D)||close Ca2+ channels, causing decreased Ca2+ entry and a faster rate of spontaneous depolarization|
What is the effect of norepinephrine on the heart?
|A)||It decreases the rate and strength of contraction.|
|B)||It increases the rate and strength of contraction.|
|C)||It decreases the amount of blood pumped per minute.|
|D)||It has no effect on the heart.|
The amount of blood in the ventricles just before they contract is called the
|A)||end diastolic volume|
|B)||end systolic volume|
If the heart rate is 70 beats per minute and stroke volume is 70 ml, then
|A)||ESV is 140 ml|
|B)||ESV is 1 ml|
|C)||CO = 4900 ml/min|
|D)||CO = 140 ml/min|
The amount of blood ejected from the heart in one minute is called the
|B)||end diastolic volume|
|C)||end systolic volume|
Which choice would not increase cardiac output?
|A)||increase heart rate, increase stroke volume|
|B)||increase heart rate, no change in stroke volume|
|C)||no change in heart rate, increase stroke volume|
|D)||decrease heart rate, no change in stroke volume|
Cardiac output from the left ventricle is
|A)||normally greater than that of the right ventricle|
|B)||probably lower than the right ventricle if the person has systemic edema|
|C)||probably lower than the right ventricle if the person has pulmonary edema|
|D)||probably higher than the right ventricle if the person has pulmonary edema|
Joe's cardiac output at rest is 5 L/min. When he is exercising strenuously it is 20 L/min. What is Joe's cardiac reserve?
Based on the information given below, which individual has the greatest tolerance for strenuous exercise? Assume they are similar in terms of size and muscular fitness.
|A)||Ann, cardiac reserve = 8 L/min|
|B)||Betsy, cardiac reserve = 15 L/min|
|C)||Carla, cardiac reserve = 18 L/min|
|D)||Donna, cardiac reserve = 25 L/min|
Any factor that alters heart rate is called
Which of the following is not a positive chronotrope?
Any factor that causes a change in heart contractility is called
At a heart rate above 180 beats per minute, all of these decrease except
|D)||end systolic volume|
The higher the _____, the greater the cardiac output.
|A)||extracellular K+ concentration|
|B)||blood pressure in the aorta|
|D)||level of acetylcholine released at the SA node|
With respect to the effect on cardiac output, the term preload refers to
|A)||the force developed by the myocardial cells during ventricular systole|
|B)||the blood pressure in the aorta and pulmonary trunk during ventricular systole|
|C)||the amount of tension developed in the myocardium before it contracts|
|D)||anything that decreases stroke volume|
Phophodiesterase is the enzyme that degrades cAMP. A drug that inhibits phosphodiesterase would have what effect on the heart?
|A)||It would decrease cardiac contractility by causing increased removal of Ca2+ from the cell.|
|B)||It would increase heart rate but have no effect on contractility.|
|C)||It would have no effect, because cAMP is not involved in altering cardiac contractility|
|D)||It would increase cardiac contractility by prolonging Ca2+ availability inside the cell.|
Slowing the heart while holding the rate of venous return (ml/min) constant would cause
|A)||decreased cardiac output|
|B)||increased cardiac output|
|C)||no change in cardiac output, because heart rate is not increased|
|D)||no change in cardiac output, because stroke volume is not increased|
Stroke volume times heart rate equals
|C)||end systolic volume|
Which of the following would not increase stroke volume?
|A)||increased venous return|
|B)||increased sympathetic stimulation of the myocardium|
|C)||increased end diastolic volume|
|D)||increased arterial blood pressure|
The Frank-Starling law of the heart says that the higher the end diastolic volume, the
|A)||lower the cardiac output|
|B)||higher the end systolic volume|
|C)||lower the blood pressure|
|D)||higher the stroke volume|
In response to exercise, the heart would be called upon to _____ the amount of blood pumped, and this would be initiated by signals from ______ fibers.
Which of the following would be an effect of cutting the vagus nerve?
|A)||reduced heart rate|
|B)||increased heart rate|
|C)||reduced strength of contraction|
|D)||increased secretion of acetylcholine|
Inhibition of the SA node by the parasympathetic division of the ANS is called
In response to an elevation in blood pressure, the cardiac control center would attempt to restore homeostasis primarily through
|A)||sympthetic stimuli to the ventricular myocardium|
|B)||sympathetic stimuli to the SA node|
|C)||parasympathetic stimuli to the SA node|
|D)||parasympathetic stimuli to the ventricular myocardium|
The ANS is the main extrinsic control for cardiac activity, acting through both sympathetic and parasympathetic fibers innervating the heart. This control system is not symmetric--one part of the ANS has less control over the heart. Which of the following statements is NOT correct?
|A)||The sympathetic division has significant control of heart rate through its action at the SA node.|
|B)||The sympathetic division has significant control of contractility through its action on the ventricular myocardium.|
|C)||The parasympathetic division has significant control of heart rate through its action at the SA node.|
|D)||The parasympathetic division has significant control of contractility through its action on the ventricular myocardium.|
Which ionic imbalance would decrease the strength of cardiac muscle contraction?
Damage to which of the following parts of the brain would cause the body to have less control over cardiac activity?
Increased input from the baroreceptors to the cardiac control center would cause which of the following to occur?
|A)||increased sympathetic stimulation and decreased parasympathetic stimulation|
|B)||increased sympathetic stimulation and increased parasympathetic stimulation|
|C)||decreased sympathetic stimulation and increased parasympathetic stimulation|
|D)||decreased sympathetic stimulation and decreased parasympathetic stimulation|
Which of the following commonly increases with age?
|A)||size of the left ventricle|
|B)||size of the right ventricle|
|D)||flexibility of heart valves|
Which of the following commonly decreases with age?
|A)||the size of the left ventricle|
|B)||size of the right ventricle|
|D)||oxygen consumption by the myocardium|