Multiple Choice
Which of the following correctly identifies a difference between action potentials in cardiac and skeletal muscle?
18. The Heart
Cardiac Action Potentials
Back18. The Heart
Cardiac Action Potentials
- Multiple Choice
Calcium ion channels open in response to changes in membrane potential. What type of opening mechanism do calcium ion channels in cardiac muscle exhibit?
- Multiple Choice
Autorhythmicity is a unique feature of cardiac pacemaker cells. What feature of cardiac pacemaker cells allows them to be autorhythmic while other cardiac cells are not?
- Multiple Choice
Cardiac contractile tissue uses sodium, calcium, and potassium channels for depolarization and repolarization. During which phase of the action potential is the calcium channel open?
- Multiple Choice
How would you expect the absolute refractory period of a contractile cell to change if more potassium channels opened sooner after polarization?
- Multiple Choice
The movement of ions in opposite directions at the same time is responsible for which of the following?
- Multiple Choice
Which statement below correctly describes how the channels that are active during the pacemaker potential are different from other ion channels used in action potentials?
- Open QuestionMultiple ChoiceMore than one choice may apply.Which of the following depolarizes next after the AV node?a. b. c. d. e.
- Open QuestionThe 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.
- Open QuestionIn the heart, which of the following apply? (1) Action potentials are conducted from cell to cell across the myocardium via gap junctions, (2) the SA node sets the pace for the heart as a whole, (3) spontaneous depolarization of cardiac cells can occur in the absence of nerve stimulation, (4) cardiac muscle can continue to contract for long periods in the absence of oxygen.a. all of the above,b. 1, 3, 4, c. 1, 2, 3, d. 2, 3.
- Open QuestionWhat is the cardiac cycle? What phases and events are necessary to complete a cardiac cycle?
- Open QuestionWhich of the following is longer? (a) the refractory period of a cardiac contractile cell, (b) the refractory period of skeletal muscle fiber.
- Open QuestionDescribe the function of the SA node in the cardiac cycle. How does this function differ from that of the AV node?
- Open QuestionWhat are the sources and significance of the four heart sounds?
- Open QuestionDescribe the effects of epinephrine, norepinephrine, glucagon, and thyroid hormones on the contractility of the heart.