PNS/ANS (year 2) Flashcards
what is the neurotransmitter released at neuromuscular junctions?
acetylcholine
what do cholinergic drugs do?
inhibit, enhance, or mimic the action of acetylcholine
what are the two types of acetylcholine receptors?
muscarinic and nicotinic
what do adrenergic drugs do?
inhibit, enhance, or mimic the action of (nor)adrenaline
name the catecholamines
adrenaline and noradrenaline
what are the types of catecholamine postsynaptic receptors?
alpha (1/2) and beta (1/2/3)
where are alpha1 receptors mainly found?
sympathetic target tissue
where are alpha2 receptors mainly found?
GI tract and pancreas
where are beta1 receptors mainly found?
heart muscle
where are beta2 receptors mainly found?
blood vessels and smooth muscle
what are two groups of drugs that could be used on the somatic nervous system?
neuromuscular blocking drugs
anticholinesterases
what drug is used in the management of skeletal muscle spasms?
dantrolene
what is the mechanism of action of dantrolene?
uncouples excitation/contraction by preventing the release of calcium ions from the sarcoplasmic reticulum
how is dantrolene administered?
orally or injectable
what is the main adverse effect of dantrolene?
muscle weakness that may effect the respiratory muscles
what are the two mechanism of action of neuromuscular blocking drugs?
depolarising blocking agents
non-depolarising blocking agents
what is the mechanism of action of depolarising neuromuscular blocking agents?
these are agonists of acetylcholine but have a longer duration of effect. They cause calcium to be taken up by the sarcoplasmic reticulum causing relaxation, then when Ach binds there is no calcium for contraction
what is the mechanism of action of non-depolarising neuromuscular blocking agents?
competitive agonists
which neuromuscular blocking drugs are reversible?
non-depolarising by acetylcholinesterase drugs
when are neuromuscular blocking drugs used?
in combination with anaesthetic drugs to provide muscle relaxation during surgery
what are the adverse effects of depolarising neuromuscular blocking agents?
bradycardia, muscle pain due to initial muscle fasciculations
what are the adverse effects of non-depolarising neuromuscular blocking agents?
hypotension
what is the mechanism of action of anticholinesterases?
acetylcholinesterase usually rapidly hydrolyses acetylcholine before much of it reaches a receptor, this prevents the hydrolysis allowing more action potentials
what are two examples of anticholinesterases?
edrophonium
organophospahte
what are the main uses of anticholinesterases?
antagonisms of non-depolarising neuromuscular blockers
treat myasthenia gravis
what are the adverse effects of anticholinesterases?
effect central cholinergic receptors leading to nausea, vomiting, diarrhoea, hypersalivation
can lead to muscle cramps, bradycardia, hypotension, miosis, bronchoconstriction
what neurotransmitter do all preganglionic neurones of the ANS release?
acetylcholine
what neurotransmitter do all postganglionic neurones of the parasympathetic system release?
acetylcholine
what are the classes of drug that effect cholinergic transmission?
muscarinic agonist/antagonist
neuromuscular blocking drugs
ganglion stimulating/blocking drugs
anticholinesterase
what is the mechanism of action of muscarinic agonists?
stimulate postganglionic muscarinic receptors
what are the main uses of muscarinic agonists?
CV - cardiac slowing and decrease CO
smooth muscle - contracts and causes vasodilation in vascular smooth muscle
exocrine - increase sweating/salivation/bronchial secretions
eye - contract ciliary muscles, miosis, glaucoma
treat detrusor muscle atony
what are the adverse effects of muscarinic agonists?
GI cramping, hypersalivation, bradycardia
what is the mechanism of action of muscarinic antagonists?
competitively inhibit postganglionic muscainic receptors
what are the main effects of muscarinic antagonists?
increase HR
decrease salivary, bronchial, gastric secretions
bronchodilation
decrease GI motility
what are the main uses of muscarinic antagonists?
GI - antispasmodic in horses
CV - correct bradycardia
ophthalmic - dilate pupil
urinary - decrease detrusor muscle activity
what are the adverse effects of muscarinic antagonists?
tachycardia, dry mouth, constipation, photophobia
when may ganglion-stimulating/blocking drugs be used?
in anthelmintics causing worm muscle paralysis
not absorbed by host as effects are complex and systemic
where is adrenaline released from?
adrenal medulla
where is noradrenaline released from?
postganglionic neurones of the sympathetic system
what are the two types of adrenergic receptors?
alpha and beta
what are the subtypes of alpha and beta receptors?
alpha 1, 2
beta 1, 2, 3
what are the main effects of alpha1 adrenoreceptors?
vasoconstriction
relax GI smooth muscle
salivary secretion
hepatic glycogenolysis
what are the main effects of alpha2 adrenoreceptors?
inhibit neurotransmitter release
what are the main effects of beta1 adrenoreceptors?
increase cardiac rate and force
what are the main effects of beta2 adrenoreceptors?
bronchodilator
vasodilation
inhibit GI smooth muscle
hepatic glycogenolysis
what are the main effects of beta3 adrenoreceptors?
thermogenesis
name the types of drugs that effect adrenergic transmission
alpha adrenoreceptor agonist/antagonist
beta adrenoreceptor agonist/antagonist
drugs effecting noradrenaline synthesis, storage, release
name the non-specific adrenergic agonist
adrenaline
when may adrenaline be used clinically?
reduce bronchospasm
treat hypersensitivity
reduce cutaneous bloodflow
restore cardiac activity after cardiac arrest
give examples of the systems that alpha adrenoreceptor agonists can be used on
smooth muscle, GI, metabolism, nerve terminals, urinary, eye, CV, sedative
what is the effect of alpha adrenoreceptors agonists on smooth muscle?
contraction - except GI
what is the effect of alpha adrenoreceptors agonists on the GI system?
relax smooth muscle/sphincters
what is the effect of alpha adrenoreceptors agonists on metabolism?
stimulate glycogenolysis
what is the effect of alpha adrenoreceptors agonists on nerve terminals?
inhibitory effect on both cholinergic and noradrenergic nerve terminals
what is the effect of alpha adrenoreceptors agonists on the urinary system?
treat incontinence
what is the effect of alpha adrenoreceptors agonists on the eye?
mydriatic effect
what is the effect of alpha adrenoreceptors agonists on the CV system?
treat hypotension secondary to drug or vascular failure
how do alpha adrenoreceptors agonists work as sedatives?
act peripheral and centrally as alpha2 adrenoreceptors
what are the main adverse effects of alpha adrenoreceptor agonists?
restlessness and hypertension
what are the main uses of alpha adrenoreceptor antagonists?
treat urethral spasm
treat severe hypertension
reverse sedation from alpha2 agonists
what are the adverse effects of alpha adrenoreceptor antagonists?
due to alpha adrenoreceptor blocking - tachycardia, hypotension, nasal congestion
what 3 systems to beta adrenoreceptor effect?
smooth muscle, CV, metabolism
what effects do beta adrenoreceptor agonists have on smooth muscle?
relaxation - bronchodilator, vasodilation
what effects do beta adrenoreceptor agonists have on the CV system?
increase HR and contraction forces
what effects do beta adrenoreceptor agonists have on metabolism?
glycogenolysis, lipolysis, thermogenesis
what are the adverse effects of beta adrenoreceptor agonists?
hypotension, tachycardia
what effects do non-selective beta blockers have?
block bronchodilation
block chronotropic and inotropic effects
manage cardiac arrhythmias
what are beta1 blockers used for?
treat tachycardia and hyperthyroidism
what are the adverse effects of beta blockers?
bradycardia, hypotension, hypoglycaemia, bronchospasm
name a drug that stimulates endogenous release of noradrenaline
ephedrine
what is ephedrine used to treat?
hypotension and urinary incontinence
name a drug that inhibits phosphodiesterase III?
pimobendan
what is pimobendan used for?
positive inotrope and vasodilator
name a phosphodiesterase V inhibitor
sildenafil
what is sildenafil used for?
treat pulmonary arterial hypertension