THE PARASYMPATHETIC NERVOUS SYSTEM: POINTS RELEVANT FOR THE ANESTHESIOLOGIST

🎳The anterior hypothalamus controls the parasympathetic nervous system

🎳The posterior and lateral hypothalamic areas increase blood pressure and heart rate, whereas the preoptic area decreases blood pressure and heart rate.
🎳The parasympathetic nervous system arises from neurons in the brainstem and spinal cord sacral segments (S 2 –S 4 ). As the parasympathetic ganglia are located near or within their effector organs, the parasympathetic postganglionic fibres are short, and they all release acetylcholine. The distribution of parasympathetic outflow is restricted so that parasympathetic effects are more localized than sympathetic effects.
🎳Cranial nerves 3, 7, 9 and 10 have parasympathetic components (3 – pupil and ciliary body constriction; 7 – tearing and salivation; 9 -salivation: 10 – the vagus and its ramifications).. Preganglionic fibres of the third cranial nerve arise from the oculomotor nucleus and pass through the orbit to the ciliary ganglion. Postganglionic f ibres from the ciliary ganglion supply the ciliary muscle and sphincter of the iris and constrict the pupils.
🎳Preganglionic fibres from the superior salivary nucleus of the seventh nerve form the chorda tympani and reach the submaxillary ganglion via the lingual nerve. Postganglionic fibres supply the submaxillary and sublingual salivary glands and cause salivary secretion. #TheLayMedicalMan 
🎳Preganglionic fibres arising from the inferior salivary nucleus of the ninth nerve form the lesser superficial petrosal nerve and reach the otic ganglion. The postganglionic fibres are distributed to the parotid gland via the auriculotemporal nerve and also cause salivary secretion.
🎳The vagus nerve is the major part of the cranial parasympathetic outflow. The preganglionic fibres arise from the dorsal nucleus of the vagus in the medulla and terminate in the ganglia of plexuses or in the walls of visceral organs. Postganglionic fibres supply the heart and decrease cardiac excitability, contractility, conductivity and rate. Postganglionic fibres from the pulmonary plexus contract the circular muscles of the bronchi, producing bronchoconstriction. Vagal branches to the gastric plexus give rise to postganglionic fibres to the stomach, liver, pancreas and spleen. Stimulation of the vagus causes increased gastric motility and secretions, with relaxation of the pyloric sphincter. The intestinal branches of the vagus supply the small and large intestines down to the transverse colon and it’s stimulation increases peristalsis and relaxes the ileocolic sphincter. #TheLayMedicalMan 
🎳The sacral outflow of the parasympathetic system arises from the second, third and fourth sacral segments of the spinal cord, and fibres enter the hypogastric plexus to innervate the descending colon, rectum, bladder and uterus. It’s stimulation contracts the muscular wall of the rectum, relaxes the internal sphincter of the anus and contracts the detrusor muscle of the bladder wall. 
Ref: Principles of Physiology for the Anaesthetist , 3/e
#physiology , #anaesthesia

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s