Which neurotransmitter is primarily secreted by the sympathetic system?

The sympathetic nervous system primarily utilizes norepinephrine as its main neurotransmitter. This system is part of the autonomic nervous system, which controls involuntary body functions. When the sympathetic system is activated, especially in response to stress or perceived threats, norepinephrine is released from postganglionic neurons. This neurotransmitter plays a crucial role in the "fight or flight" response, leading to increased heart rate, heightened alertness, and mobilization of energy stores among other physiological changes.

Norepinephrine acts on various adrenergic receptors throughout the body, initiating processes such as vasoconstriction and increased cardiac output, which prepare the body to respond effectively to perceived dangers. Understanding norepinephrine's role in the sympathetic nervous system is essential for comprehending how the body reacts in stressful situations and maintains homeostasis under varying conditions.