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

The sympathetic nervous system is part of the autonomic nervous system and plays a crucial role in the body's response to stress or emergency situations, often referred to as the "fight or flight" response. When activated, the sympathetic nervous system releases neurotransmitters such as norepinephrine, which bind to receptors on the heart. This interaction increases the heart rate by enhancing the force of contractions and the speed of electrical impulses through the heart's conduction system.

The increase in heart rate is a vital physiological adjustment that prepares the body for rapid action, allowing it to meet increased metabolic demands during stress or physical activity. It also promotes blood flow to vital organs and muscles by increasing cardiac output. This mechanism demonstrates how the sympathetic nervous system dynamically regulates cardiovascular function to optimize the body's response to various demands.