Muscarinic Receptors Flashcards
Categories of nerves
Peripheral=around the medulla
Somatic = skeletal muscle
Parasympathetic and sympathetic systems
What is the autonomic nervous system
Subconscious control of organs and homeostasis
Controls output from the CNS to body with somatic intervention
Vegus nerve controls heart rate using secretions
Enteric branch of ANS
Cell bodies in the wall of the GI tract receive sympathetic and parasympathetic input
Can innervate blood vessels, smooth muscles and glands
Utilises neurotransmitters (ACh, noreadreneline, non-adrenic non-cholinergic)
Can control GI function without external input
Stimulation
Sympathetic and parasympathetic stimulation happen as opposing actions
Organs like sweat glands and blood vessels are sympathetic
Ciliary muscles of the eye are only parasympathetic
What are the two neurones in a neurone system
Pre and post ganglionic
Pre-ganglionic neurones
Cell body in the CNS Small diameter Myelinated Synapses are autonomic ganglia Preganlionic foibles release ACh
Post- ganglionic neurones
Cell bodies in autonomic ganglions
Small diameter
Unmyelinated
Terminal synapse close to target organ
Adrenal medulla
Specialised ganglion
Chromaffin cells are specialised post-synaptic neurones
M1, M3, M5
All have the same signalling system using G-couples receptors
M1, M3, M5 = activated
All increase IP3 stimulation and increase calcium
M2, M4
All have an enzymes inhibited coupling method
M2, M4 = inhibited
Cause slowing of the heart
Function of M1
Gastric
Salivary
Function of M3
Exocrine glands
Smooth muscle
Blood vessels
Function of M5
Salivary glands
Iris
Ciliary muscle
Function of M2
Cardiac
Presynaptic
Reduce cAMP
Reduce concentration of calcium ion conductance
Increase concentration of potassium ion conductance
Function of M4
CNS
Decreases cAMP
Parasympathetic effects
Increased salivation Increased mucus secretion Increased gastric secretion Increased GI motility Increased urination Increased bronchoconstriction Decreased HR and AVN conduction Increased penile erection Increased tears
What is muscadine poisoning
Excessive parasympathetic responses
What does SLUDGE stand for
Salivation Lacrimation Urination Diarrhoea Gastric upset Enesis
What does DUMBBELLS stand for
Diarrhoea Urination Miosis Bradycardia Bronchoconstriction Emesis Lacrimation Salvation
Mimicking ACh
Some drugs act directly on muscarinic receptors like muscurinic agonists (parasympathomimetic) and muscurinic antagonists (parasympatholytic)
Agonists on muscorinic/nicotinic/ACh receptors:
Acetylcholine
Methacholine
Agonists on muscurinic/nicotinic
Carbachol
Agonists on muscarinic
Bethanechol
Pilocarpine
Effect of muscarinic antagonists
Inhibit secretions Cause tachycardia Mydriasis Inhibit GI motility Relax smooth muscle Bronchodilators CNS excitation
Muscurinic antagonists
Block ACh action
Non-selective competitive antagonists
Readily absorbed, penetrate BBB
Act as CNS stimulant, delirium and hallucinations
Treats ACh poisoning and GI hypermotility
Main side effects are urine retention, dry mouth, blurred vision
Hyoscine
Muscurinic antagonist
Non-selective competitive antagonist
GI relaxant and anti-secretory
Blocks transmission from vestibular apparatus to vomiting centre
ACh analogies clinical uses
Bladder emptying
Glaucoma
Slow heart, vasodilation, sweating/salivation/secretion
Summary of antagonists
Prevent para-sympathetic responses like inhibiting secretions
Useful in surgery
Tachycardia, optical uses, airway disease like COPD, decrease GI motility
