What neurotransmitter do post-ganglionic parasympathetic fibers release?

Post-ganglionic parasympathetic fibers release acetylcholine as their primary neurotransmitter. This release occurs at the target organs where the fibers exert their effects, influencing various physiological processes such as decreased heart rate, increased glandular secretion, and enhanced gastrointestinal motility.

The use of acetylcholine by the parasympathetic nervous system is consistent with its role in promoting "rest and digest" functions, contrasting with the sympathetic nervous system which predominantly utilizes norepinephrine to elicit the "fight or flight" response.

Understanding the neurotransmitter types and their respective functions is crucial for comprehending the division of the autonomic nervous system and the specific actions they govern in the body. Acetylcholine's role in synaptic transmission in both the central and peripheral nervous systems highlights its importance in overall physiological regulation.