Cholinergic System Flashcards
There are two types of Cholinergic receptors they are
Muscarinic receptors
Nicotinic receptors
All subtypes of muscarinic receptors are sensitive to
Atropine
Muscarinic receptors found predominantly in the heart is
M2
What Muscarinic receptors are found in glandular tissues, smooth muscles and endothelium
M3
Nicotinic receptors are said to be pentamers because
They consist of 5polypeptide chains
There are two types of Nicotinic receptors namely
Nm
Nn
What type of Nicotinic receptors are located in skeletal muscle at the neuromuscular junction
Nm
Drugs affecting Cholinergic mechanisms are classified into two main groups
Drugs that mimic the action of Ach
Substances that inhibit cholinesterases or enzymes that metabolize Ach
Drugs that mimic the action of Ach can be divided into
•Choline esters; Ach, Metacholine, buthanecol
•Alkaloids; pilocarpine, nicotine
Substances which inhibit the cholinesterases are divided into
•Short acting: Alcohol, Edrophonium
•Intermediate acting: Neostigmine, pyridostigmine, Physiostigmine
•Very long acting; Organophosphate, Echothiophate, Parazosin
Cholinergic antagonists that block Muscarinic receptors
Tenezepine
Atropine
Dicyclomine
Scopolamine
Homatropine
Hyoscine
Prenzepine
Cholinergic antagonists that block Nicotinic receptors in the ganglia
Hexamethonium
Trimethophan
Tetraethylammonium
Nicotinic receptor antagonist at the motor end plate
Tubocurarine (flaccid paralysis)
Suxamethonium (spastic paralysis)
Effect of Cholinergic drugs on CVS
Hypotension
Vasodilation
Decreased cardiac rate
Effect of Cholinergic drugs on GIT
Increase motility
relaxation of sphincters
Effect of Cholinergic drugs on Respiratory System
Constricts bronchial muscles
Induce secretion
ContraIndicated in asthmatics
Effect of Cholinergic drugs on Urinogenital tract
Promotes micturition by relaxing trigone and sphincter muscle of bladder..also stimulating detrusor muscle
Effect of Cholinergic drugs on the eye
Myoses..reduction of IOP
Effect of Cholinergic drugs on salivary gland
Stimulates secretory actions of lacrimal, sweat and nasopharyngeal glands..gastric juice is secreted
ContraIndications of Cholinergic drugs
Asthma
Acute iritis
Narrow angle glaucoma
Hyperthyroidism
Two types of cholinesterase found in the body
True/Specific cholinesterase
Pseudo /Serum Cholinesterase
AntiCholinesterase drugs are divided into three namely
- Carbamate esters :Physiostigmine, neostigmine, pyridoxstigmine
- Quartnary alcohol: Edrophonium
- Organophosphate: Echothiophate, parathiol, malathion
An example of an Irreversible anticholinesterase agent
Malathion
Parathion
Group of compounds capable of regenerating the active enzyme from organophosphate
Oximes; Pralidoxime, diacylmonoxime, Obidoxime
The most potent oxime used is
Obidoxime
The most extensively used is
Pralidoxime
Substances which inhibit release of ACh
Hemicholinium and magnesium
