If a nerve to an isolated heart is stimulated and the heartbeat slows,the most reasonable conclusion is that the heart
A) is responding to a nerve control that inhibits heartbeat.
B) is dying since nerves can only stimulate muscle action.
C) is unaffected by the nerve but responding to some unknown chemical factor.
D) is normal as all nerve stimulation results in decreased muscle activity.
E) None of the choices are correct.

Question

Quizplus · Accepted Answer

Stimulation of a nerve to the heart can either increase or decrease the heart rate. If the heartbeat slows down, it suggests that the nerve is carrying signals that inhibit the heart's activity. This is a normal response known as parasympathetic activity, which is mediated by the vagus nerve. Therefore, the most reasonable conclusion is that the heart is responding to a nerve control that inhibits heartbeat.

If a Nerve to an Isolated Heart Is Stimulated and the Heartbeat