Parasympathetic Nerve Fibers (PNS Fibers)

Parasympathetic nerve fibers are cholinergic autonomic nerves originating from craniosacral regions. They mediate rest-and-digest physiological responses via acetylcholine acting on muscarinic receptors throughout various organ systems—most notably via cranial nerves including a dominant role for the vagus nerve in thoracic/abdominal viscera control. These fibers are crucial for maintaining homeostasis by counterbalancing the sympathetic nervous system's fight-or-flight responses. They influence heart rate, digestion, glandular secretion, urinary function, and airway tone.

Other names

Cholinergic Autonomic NervesCraniosacral NervesRest and Digest Nerves

Acetylcholinesterase inhibitors increase acetylcholine levels at the synapse by inhibiting its breakdown. Muscarinic agonists directly stimulate muscarinic acetylcholine receptors. Muscarinic antagonists block muscarinic acetylcholine receptors, preventing acetylcholine from binding and exerting its effects.