What effect does the sympathetic nervous system have on heart rate?

The sympathetic nervous system plays a vital role in the "fight or flight" response, which prepares the body for situations requiring increased alertness, physical activity, or stress. When activated, it releases neurotransmitters like norepinephrine that bind to receptors in the heart, leading to an increase in heart rate. This is crucial during stress or emergencies, as a faster heart rate allows more oxygenated blood to be pumped to muscles and vital organs, enhancing physical performance.

The options that suggest a decrease or no effect on heart rate do not align with the physiological responses associated with sympathetic activation. While the heart rate can be regulated by various systems, the specific effect of the sympathetic nervous system is an increase in heart rate to prepare the body for action.