parasympathetic outflow
Quick Summary
The parasympathetic nervous system is a division of the autonomic nervous system that controls involuntary bodily functions, primarily affecting visceral organs like glands. Unlike the sympathetic nervous system, which prepares the body for "fight or flight," the parasympathetic system is not essential for immediate survival but plays a crucial role in maintaining homeostasis.123
Anatomy and Function
The parasympathetic nervous system's motor component consists of preganglionic and postganglionic neurons. Preganglionic neurons originate in the brainstem or the sacral segments of the spinal cord, leading to the system being called the "craniosacral outflow". These neurons project to ganglia located near or within the target organs. Both pre- and postganglionic neurons release acetylcholine as a neurotransmitter.12456
Key functions include:
* Regulating the iris and lens of the eye.1
* Stimulating glands such as the lacrimal, salivary, and nasal mucous glands.12
* Slowing heart rate and increasing digestive secretions.723
The parasympathetic system generally works in opposition to the sympathetic nervous system.53
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