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WEEK 6:
Autonomic Pharmacology:
| Question | Answer |
|---|---|
| adrenergic receptors | receptors on cell surface responding to adrenaline/epinephrine and noradrenaline/norepinephrine |
| alpha-1 receptor stimulation leads to (5) | vasoconstriction, increase peripheral resistance (blood flow), mydriasis (pupil dilation), increase closure of bladder sphincters |
| alpha-2 receptor stimulation leads to (3) | inhibits norepinephrine release, inhibits Ach release, inhibits insulin release |
| beta-1 receptor stimulation leads to (4) | increase heart rate, increase myocardial contractility, increase lipolysis, increase renin |
| beta-2 receptor stimulation leads to (6) | vasodilation, decrease peripheral resistance, bronchodilation, increase glycogenolysis (in muscle + liver), increase glucagon release, relaxes uterine smooth muscle |
| neurotransmitter which works best in alpha 1 | NE>E |
| neurotransmitter which works best in alpha 2 | E>N |
| neurotransmitter which works best in beta 1 | E=NE |
| neurotransmitter which works best in beta 2 | E>>NE |
| B1 'cardiac' signaling mechanisms | increased cAMP -> increased PKA -> increased phosphorylation of Ca2+ channels + activate them -> increase Ca2+ influx -> cardiac contraction |
| B2 'smooth muscle' signaling mechanisms | increase cAMP -> increase PKA -> increase phosphorylation of contractile proteins -> smooth muscle relaxation |
| A1 'smooth muscle' signaling mechanisms | increase Ca2+ -> smooth muscle contraction |
| A2 'smooth muscle' signaling mechanisms | decreases cAMP -> decreases PKA -> decreases phosphorylation of contractile proteins -> smooth muscle contraction |
| indirectly acting sympatholytics | drugs that inhibit noradrenaline synthesis |
| indirectly acting sympathomimetics | drugs that interfere with NA storage, promote NA release, reduce NA reuptake (eg cocaine) |
| propranolol | non selective B blocker (bind to both B1+B2 receptors) + administered orally |
| why should you not prescribe propranolol to an asthmatic who has IHD | propranolol is a B2 antagonist -> block B2 receptor -> bronchoconstriction -> bronchospasm |
| how do you treat an asthmatic who has IHD | use atenolol (antagonist which is cardiac selective at B1) |
| indirectly acting sympathomimetic drugs examples (3) | amitriptyline, amphetamine, cocaine |
| indirectly acting sympathomimetic drugs pathway | (1- tyrosine is synthesised into NA which is stored into vesicles using VMAT) (2- AP causes NA to leave + bind to either B (tachycardia) or A (vasoconstriction) receptor) (3- NA reuptake or broken down by MAO into metabolites) |
| atropine | blocks effects of parasympathetic pathway (antimuscarinic) |
| symptoms showing affected parasympathetic nervous system/ atropine poisoning | mydriasis (dilated pupils), blurred vision, tachycardia, hot but not sweaty, dry mouth, urinary urgency + no retention, excitable, disorientated, like they have eaten berries |
| mydriasis meaning | dilated pupils |
| how does atropine poisoning work | block peripheral Ach receptors (so affect mAChR) parasympathetic effects but does not effect nAChR so NMJ is not affected |
| when M3 'glandular' receptor is stimulated what happens | increase Ca2+ leading to exocrine secretion and smooth muscle contraction |
| when M2 'cardiac' receptor is stimulated what happens | decrease cAMP -> decrease PKA -> decease phosphorylation of Ca2+ channels -> inactivated Ca2+ channels -> activated K+ channels -> hyperpolarise Vm -> decrease Ca2+ channel activity -> decreased rate of cardiac muscle contraction (bradycardia) |
| when M1 'neural' receptor is stimulated what happens | 'various actions' |
| parasympathetic control of bladder (autonomic reflex arc and incontinence) | stretch receptor -> pelvic sensory fibre -> fibres in thalamus -> cerebral cortex -> interneuron -> sensation to thalamus -> PNS preganglionic motor fibre in pelvic nerve -> postganglionic neuron in intramural ganglion = stimulate smooth muscle |
| antagonist to inhibit reflex arc at target organ | M3 receptors |
| oxybutynin | M2/ M3 mAChR antagonist responsible for preventing unwanted bladder contractions since antagonist is non selective |
| side effects of oxybutynin | same as atropine eg blurred vision , tachycardia and dry mouth |
| effect of M3 agonist (eg pilocarpine) on pupil and circular muscle | constriction of pupil (miosis) and contraction of circular muscle |
| effect of M3 antagonist (eg atropine) on pupil and circular muscle | dilation (contraction/ relaxation) of pupil (mydriasis) and constriction of circular muscle |
| example of M3 antagonist on pupil | atropine (now surpassed by tropicamide) |
| example of M3 agonist on pupil | pilocarpine which promotes miosis |
| glaucoma | tunnel vision and blindness due to build up on intraocular pressure which compresses optic nerve with excess aqueous humour |
| how to treat glaucoma | promotion of miosis because it constrict circular muscle and opens up drainage channel and increase aqueous humour drainage leading to decrease intraocular pressure |
| scopolamine (hyoscine) | solanaceous plant product which is non selective parasympatholytic having a higher lipophilicity > than atropine and readily crosses BBB causing CNS effects with a longer duration of action |
| use of scopolamine | CNS depressant -> sedation (inhibits smooth muscle motility) used as a patch behind the ear to prevent travel/ motion sickness and to alleviate bowel colic and dysmenorrhea (period cramp) |
| acetylcholine made of (2) | acetate and choline |
| anti-ChE (anticholinergic drugs) | REVERSIBLE competitive inhibitors which elevate Ach at synapse = MORE STIMULATION |
| physostigmine | used to increase miosis in treatment of glaucoma instead of pilocarpine and stimulate bladder in urinary retention during post operative surgery and treatment of atropine poisoning |
| neostigmine | polar, less lipohillic and acts peripherally being most effective at NMJ used to treat myasthenia gravis using AChR antibodies |
| examples of anti-chE (anticholinergic drugs) | physostigmine and neostigmine |
| antcholinesterases (AchE + Pi) | IRREVERSIBLE non competitive inhibitors which covalently modify organophosphorous compounds- AChE + Pi = irreversible. Some are highly lipid soluble and rapidly cross insect cuticles and insecticides |
| example of anticholinesterases | dyflos |
| short term effects/ symptoms of sublethal organophospho anticholinesterase poisoning | muscarinic (miosis, salivation, sweating, bradycardia) nicotinic (fasciculation - twitching of SkM due to spontaneous release of Ach and paralysis due to depolarising neuromuscular block) CNS (anxiety, restlessness, dizziness) |
| long term effects/ symptoms of sublethal organophospho anticholinesterase poisoning | demyelination of peripheral nerves (weakening and sensory loss) |
| treatment of anticholinesterase poisoning | use anti-muscarinic (parasympatholytic) eg atropine to decrease availability of mAChR and alleviate muscarinic symptoms dephosphorylate AchE with oximes eg pralixodime (but AchE-P can undergo irreversible aging) so pralidoxime has to be used quickly |
| treatment for anticholinesterase poisoning eg overdose physostigmine | use anti muscarinic eg atropine to decrease availability of Ach receptors |
| treatment for atropine poisoning | cholinesterase inhibitor eg physostigmine to increase availability of Ach |
| therapeutic treatment examples for hypertension | drugs which inhibit a-adrenoceptors causing vasoconstriction in periphery eg oxazosin and prazosin (doxazosin in renal patients) |
| major side effect with a1 antagonists | postural hypotension leading to decrease vasoconstriction that occurs when standing up, decrease BP, and dizziness and possible fainting on standing up (reduces with long term use) |
Created by:
kablooey
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