Question

Describe the action of cholinergic & adrenergic blocking agents & give at least one example of each.

Answer 1

Anticholinergic block acetylcholine from binding to its receptor on certain nerve cells .They inhibit actions of parasympathetic nerve impulses .these nerve impulses are resposible for involuntary muscle movement in the ;gastrointestinal tract

Anticholinergic is mainly classified into anti muscarnic and anti nicotinic

muscarnic receptors are found on nerve endings to smooth muscle cells ,seretory galnds and the eye and also in CVS.Nicotinic acetylcholine receptors are located at the nerve endings of neuromuscular junctions and are the target of muscle relaxing drugs.

They have various actions on each parts.
CNS-control tremor and rigidity of Parkinsonism.example includes atropine,
CVS-At low dose,bradykardia produced,later Tachycardia.example includes atropine
Eye-Passive mydriatic effect,cyclopegia.examples are atropine,
Respiratory system-Relaxes bronchial smooth muscles.examples are atropine
Urinary Tract-Decrease the tone of detrusor muscle.examples are atropine
GIT-decreased peristalsis but increased sphincter tone.examples are atropine
Exocrine-decreased secretion of exocrine glands.example includes atropine

2types of adrenergic blockers.-alpha and beta.
In the case of alpha blockers,it blocking the effect of nevrvous in the sympathetic nervous system by binding to alpha receptors in smooth muscles or blood vessels,it can bind both reversibly or irreversibly

its action is studied in
Eye-miotic effect.examples are phentolamine
GIT-increased GI motility and relaxation of sphincter.phentolamine
Reproductive-In vas deferns,impaired ejaculation and impotence.example are phentolamine
Urinary Tract-Relaxation of trigone and sphincter.example are tamsulosin
Arteries-decrease in after load and BP by alpha 1,tachycardia and palpitation by alpha 2
Veins-decreased preload. Example is phenoxybenzamine

Beta adrenergic blockers are drugs that bind to beta-adrenoreceptors and there by block the binding of norepinephrine and epinephrine

Beta adrenergic blocker-Its actions lies in-

CVS-
1.Heart-beta receptors are linked with G protein couples receptors on activation due to increased CAMP and this leads to increased phosphrylation of calcium and hence opening of L-type calcium channels thereby increasing heart rate ,when blocked decreasing heart rate .example includes propanolol
2.Blood vessels-Initially increased Peripheral vascular resistance,then falls leading to decreased BP as beta 2 blocked,also reduce renin is beta 1 blocked.examples are propanolol

Respiratory system-causes bronchospasm.example, atenolol,metoprolol
Skeletal muscle-skeletal muscle tiredness and weakness.example propanolol
Metabolic effects-Inhibit glycogenolysis ,hence delay recovery from Hypoglycemia.example propanolol
Eye-decrease IOP by reducing secretion of aqueous humour.example timolol