Which pair accurately describes the relationship between sympathetic and parasympathetic drive and heart rate?

The correct response highlights the dynamics between sympathetic and parasympathetic nervous systems and their influence on heart rate. The sympathetic nervous system is responsible for the 'fight or flight' response, which prepares the body for stress or emergencies. When this system is activated, it releases neurotransmitters like norepinephrine that increase heart rate and enhance the force of each contraction, effectively ramping up cardiovascular performance to meet the demands of the situation.

In contrast, the parasympathetic nervous system promotes 'rest and digest' functions, focusing on conserving energy and maintaining homeostasis. When the parasympathetic drive is increased, through mechanisms such as the release of acetylcholine, it works to slow the heart rate down, allowing for recovery and relaxation.

Thus, an increase in sympathetic drive—which often occurs during stress or physical activity—leads to an increase in heart rate. Conversely, an increase in parasympathetic drive results in a decrease in heart rate. This complementary relationship is crucial for maintaining balance in the body’s physiological responses.