University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

402

Pages:

2
Author:

Mariam A. A.

PSNS SYSTEM Parasympathetic nervous system (craniosacral division) • Rest and digest system – promotes maintenance activities and conserves body energy: o ↓ force and rate of cardiac output → ↓ BP o Constricted pupils and airways o ↑ activity of GIT + ↑ bile production • Vessels in muscle are NOT innervated by parasympathetic nervous system • Preganglionic neurons are located in cranial nerve nuclei of brainstem and sacral spinal cord • Preganglionic neurons are long and axons project to postganglionic neurons located in ganglia situated near or within the wall of the target organs • ACh = excitatory NT of both pre and postganglionic neurons Cranial outflow • III – pupils constrict (oculomotor) • VII – tears, nasalmucous, saliva (facial) • IX – parotid salivary gland (glossopharyngeal) • X (vagus nerve) – visceral organs of thorax and abdomen: predominant carrier of parasympathetic info in whole body o Stimulates digestive glands o Increases motility of smooth muscle of digestive tract o Decrease heart rate o Increased bronchial constriction Sacral outflow (S2-S4): form splanchnic nerves • Supplies 2nd half of large intestine • Supplies all the pelvic (genitourinary) organs Characteristic Origin Sympathetic Thoracolumbar outflow: preganglionic neurons originate in the intermediolaternal cell column of thoracolumbar spinal cord (laternal horn of gray matter) located between T1 and L3 Location of ganglia Ganglia close to CNS: alongside vertebral column (sympathetic trunk ganglia) and anterior to vertebral column (prevertebral ganglia) Short preganglionic (except splanchic nerves) and long postganglionic Relative length of pre- and postganglionic axons Branching of preganglionic axons Function Neurotransmitters Parasympathetic Craniosacral outflow: preganglionic neurons originate in the brain stem nuclei of cranial nerves III, VII, IX and X, within the intermediolatral cell column of the sacral spinal cord (S2-S4) Ganglia in or close to visceral organ served Long preganglionic, short postganglionic Extensive Minimal Prepares body to cope with emergencies and intense muscular activity – fight/flight Preganglionic neurons synapse (ACh) onto postganglionic sympathetic neurons in the paravertebral and prevertebral ganglia. Noradrenaline is the neurotransmitter at all target tissues, except for sweat glands (ACh) and adrenal medulla (adrenaline). Maintenance functions – conserves, stores energy – rest and digest Preganglionic neurons synapse (ACh) onto postganglionic parasympathetic neurons in ganglia close to the target tissue and ACh is then the neurotransmitter at all target tissue (for postganglionic neurons)