Question 37

Increased sympathetic nerve output results in a faster heartbeat.

The condition that leads to a faster heartbeat is increased sympathetic nerve output. This physiological response stimulates the heart to beat more rapidly, enhancing cardiac output.

A) Increased blood volume

Increased blood volume can lead to a stronger stroke volume but does not necessarily correlate with a faster heartbeat. While it can affect cardiac output, it does not directly increase the heart rate like sympathetic nerve stimulation does.

B) Decreased pacemaker stimulus

A decreased pacemaker stimulus would lead to a slower heartbeat. The pacemaker cells in the heart are responsible for initiating the heartbeat, and a reduction in their activity would slow down the heart rate.

C) Decreased sympathetic nerve output

Decreased sympathetic nerve output results in a lower heart rate. The sympathetic nervous system is responsible for increasing heart rate, and its reduction would lead to a decrease in heart rate rather than an increase.

D) Increased sympathetic nerve output

Increased sympathetic nerve output is the correct answer as it directly increases the heart rate. This occurs through the release of neurotransmitters like norepinephrine, which stimulate the heart to beat faster.

Conclusion

Increased sympathetic nerve output is the definitive factor that leads to a faster heartbeat, as it enhances the heart's intrinsic signaling to increase rate. Other options, including increased blood volume, decreased pacemaker stimulus, and decreased sympathetic output, either do not contribute to a faster heartbeat or actively decrease the heart rate. Thus, D is the only correct choice in this context.