parasympathetics
parasympathetics
Cholinergic effects of muscarinic receptors:
Muscarinic M1 receptor actions:
- CNS:
- ? motion sickness; Parkinsonian tremor & extrapyr.;
- ? memory function; EEG inc. voltage & freq. alpha-rhythm;
- ⇒ cortical arousal;
- produce slow excitatory post-syn. potentials → modulatory effect:
- symp.ganglia;
- post-gang. neurons of myenteric plexus;
- postganglionic intramural neurons → inc. gastric secret.
- presynaptic nerve terminals of autonomic neurons (some are M2):
- ⇒ decr. transmitter release incl. NA & ACh;
- ⇒ decr. symp. stimulation of heart, etc;
Muscarinic M2 receptors:
- heart:
- hyperpol. & decr. rate spontaneous depol. at SA node
- ⇒ delay attainment of threshold level → decr.HR;
- decr. AV conduction → may cause CHB in XS;
- inc. funct. refract. period AV node → decr. vent.resp. to AF
- decr. contract.(esp. atrial); decr. duration of AP;
- decr. effective refractory period;
- if disease or arrhythmia → partial depol. then ⇒ inc. cond. velocity in atrial muscle
- ⇒ exac. AF/flutter from ectopic focus;
- decr. automaticity of Purkinje fibres;
- inc. threshold for VF;
- decr. myocardial response to catecholamines;
- vascular:
- vasodilatation;
Muscarinic M3 receptors:
- secretion
- inc.: nose/mouth/pharynx/bronchi (incl. salivary & lacrimal), gastric; exocrine sweat glands;
- sm.muscle:
- pupil constriction; accomodation; bronchoconstriction;
- inc. GIT tone, motility; relax GIT sphincters;
- ⇒ N, belching, vomit, cramps, defecation;
- inc. urinary & biliary systems tone & contractions;
- ⇒ inc. detrussor tone but decr. trigone tone;
parasympathetics.txt · Last modified: 2009/11/12 13:45 by 127.0.0.1