In the sympathetic nervous system, what neurotransmitter is released by post ganglionic neurons?

In the sympathetic nervous system, postganglionic neurons primarily release norepinephrine as their neurotransmitter. This release of norepinephrine is critical for the sympathetic response, which prepares the body for 'fight or flight' situations. When norepinephrine is released, it binds to adrenergic receptors on target organs, resulting in various physiological changes such as increased heart rate, enhanced blood flow to muscles, and heightened alertness.

This is in contrast to the preganglionic neurons in the sympathetic nervous system, which release acetylcholine. While adrenaline, also known as epinephrine, is related and can also be released into the bloodstream from the adrenal medulla, it differs in that it is not released directly by postganglionic neurons. Serotonin, on the other hand, is primarily associated with mood regulation and is not a neurotransmitter typically involved in the sympathetic nervous system’s immediate responses. Thus, norepinephrine is the correct answer, as it plays a fundamental role in mediating the effects of the sympathetic nervous system.