For the Following Questions, Refer to the Graph of an Action

question 23

Multiple Choice

For the following questions, refer to the graph of an action potential.

-Action potentials are normally carried in only one direction: from the axon hillock toward the axon terminals. If you experimentally depolarize the middle of the axon to threshold, using an electronic probe, then

• A) no action potential will be initiated.
• B) an action potential will be initiated and proceed only in the normal direction toward the axon terminal.
• C) an action potential will be initiated and proceed only back toward the axon hillock.
• D) two action potentials will be initiated, one going toward the axon terminal and one going back toward the hillock.
• E) an action potential will be initiated, but it will die out before it reaches the axon terminal.

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Definitions:

Atrial Depolarization

The excitement and contraction caused by the SA node at the beginning of the cardiac cycle.

Cardiology

The branch of medicine dealing with disorders of the heart as well as parts of the circulatory system.

Cardiac Cycle

The sequence of events that occur in the heart during one complete heartbeat, including contraction (systole) and relaxation (diastole) phases.

Atrial Depolarization

The electrical activation of the atria of the heart, typically represented by the P wave in an electrocardiogram (ECG).