Textbook Question
More than one choice may apply.
Which of the following depolarizes next after the AV node?
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18. The Heart
Cardiac Action Potentials
Back18. The Heart
Cardiac Action Potentials
- Multiple Choice
The movement of ions in opposite directions at the same time is responsible for which of the following?
1views - Multiple ChoiceThe noncontractile cardiac muscle cells that initiate their own depolarization and cause depolarization of the rest of the heart are called __________.
- Multiple ChoiceBy what mechanism does an increase in venous return lead to an increase in stroke volume during the cardiac cycle?
- Multiple ChoiceIn the context of cardiac action potentials, what is a pulse deficit?
- Multiple ChoiceHow would a decrease in blood volume affect both stroke volume and cardiac output?
- Textbook Question
Mark the following statements as true or false. If a statement is false, correct it to make a true statement.
Pacemaker cells lack a distinct plateau phase.
- Textbook Question
Mark the following statements as true or false. If a statement is false, correct it to make a true statement.
Open sodium ion channels cause hyperpolarization in pacemaker cells, which triggers HCN channels to open and begins a new action potential.
1views - Multiple Choice
Which of the following correctly identifies a difference between action potentials in cardiac and skeletal muscle?
1views - Multiple ChoiceThe absolute refractory period refers to the time during which __________.
- Textbook Question
Describe the function of the SA node in the cardiac cycle. How does this function differ from that of the AV node?
- Textbook Question
Describe the effects of epinephrine, norepinephrine, glucagon, and thyroid hormones on the contractility of the heart.
1views - 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?
1views - Textbook Question
In 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
- Textbook Question
Mark the following statements as true or false. If a statement is false, correct it to make a true statement.
The plateau phase in contractile cells is due to the influx of calcium ions through calcium ion channels.
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