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Parasympathetic Nervous System
Aka: Parasympathetic Nervous System, Parasympathetic System, Parasympathetic Nerve
- See Also
- Autonomic Nervous System
- Sympathetic Nervous System
- Autonomic Dysfunction
- Cholinergic Toxicity
- Anticholinergic Toxicity
- Definitions
- Parasympathetic Nervous System
- Part of Autonomic Nervous System with activity that typically counters the Sympathetic Nervous System
- Energy conserving (anabolic) system activated in rest and relaxation situations
- Contrast with the Sympathetic Nervous System, an energy expending system activated in times of stress
- Physiology: Activity
- Decreases pupil size (Miosis) and contracts ciliary muscle (accommodation)
- Stimulates Salivary WATERY secretion (contrast with viscous secretion by the Sympathetic System)
- Decreases Heart Rate and Blood Pressure
- Stimulates bronchoconstriction and Bronchial gland secretion
- Increases gastrointestinal activity (peristalsis) and secretion
- Relaxes gastrointestinal sphincters (e.g. anal sphincter in Defecation)
- Stimulates Urethral relaxation and Bladder contraction
- Mediates Erection (contrast with ejaculation mediated by the Sympathetic System)
- Anatomy
- Craniosacral division of the Autonomic Nervous System
- Signals originate
- Sacral spinal cord (S2 to S4) supplies urinary and Gastrointestinal Systems
- Brain Stem nucleii (CN 3, CN 7, CN 9, CN 10)
- Vagus Nerve (CN 10) has broad, far ranging activity (lungs, heart, gastrointestinal)
- Limited roles by CN 3 (pupil/ciliary constriction), CN 7 (tears/Saliva) and CN 9 (Saliva)
- Preganglion Neurons Synapse at cranial autonomic ganglia or in terminal ganglia near target organs
- Transmitted to target organ
- Images

- Pathophysiology
- See Cholinergic Toxicity (e.g. Organophosphate Poisoning)
- See Anticholinergic Toxicity (e.g. Anticholinergic Medication)
- References
- Goldberg (2014) Clinical Neuroanatomy, Medmaster, p. 54-60
- Netter (1997) Atlas Human Anatomy, ICON Learning, p. 152-4