Introduction To ANS Flashcards
Types of Muscarinic Receptors
Functions
Receptor Mechanism
M1: Neural receptor, Gastric Secretions (IP3 DAG)
M2: Cardiac (cGMP)
M3: Glandular and smooth muscle (IP3 DAG)
M4: CNS neurons, Vagal Nerve endings (cGMP)
M5: Vascular endothelium esp. cerebral vessels (IP3 DAG)
Receptor that causes release NO
M3
Mechanism of vasodilation from M3 receptor
M3 —> IP3 DAG —> Vascular endothelium release of NO —> cGMP —> relaxation (vasodilation)
2nd messenger of parasympathetic
CGMP
2nd messenger of sympathetic
CAMP
Pirenzepine MOA and function
Selective M1 blocker
Affects secretion of Parietal cells
Gastrozepine MOA and function
Selective M1 blocker
Blocks secretion of parietal cells without affecting the GI walls
Atropine MOA and function
Non selective M blocker Blocks secretions (M1) and muscular walls (M3)
MOA of muscarinic receptors
GPCR
MOA of nicotine causes receptors
Ion channels
Location of nicotinic receptors
- All autonomic ganglia
- All somatic NMJ endings
- Some CNS neurons
Types of Nicotinic receptors, MOA and functions
NM (muscle type)- Skeletal muscle NMJ end plates (opening of N and K channels: depolarisation)
NN (neuronal type)- Ganglion receptors, Autonomic post neurons (opening of N and K channels)
Types of nicotinic receptors and structure
NM: a1 and b1 subunits in addition to gamma and delta
NN: two a3 and one b4 in addition to gamma and delta
Trimethaphan MOA and function
Block the effect of ACh on autonomic ganglia
Selective nicotinic receptor antagonist
Tubocurarine MOA and function
Selective nicotinic receptor antagonist
Block the effect of ACh on skeletal muscles
Phentolamine MOA
Non-selective alpha adrenergic antagonist
Alpha adrenoceptor interaction with adrenergic agonist in descending order of potency
Epi=nor»isoproterenol
Beta1 adrenoceptor interaction with adrenergic agonist in descending order of potency
Isoproteranol>epi>/=nor
Atenolol
Relatively selective beta blocker
Beta2 adrenoceptor interaction with adrenergic agonist in descending order of potency
Isoproteranol = epi»_space; nor
Alpha 1 and beta 2 effect on pregnant uterus
A1: uterine contraction
B2: relaxation (to delay premature labour)
Alpha 1 and beta 2 effect on vascular smooth muscle (skeletal muscle)
A1: vasoconstriction (leading to vasospasm)
B2: relaxation — vasodilation (used for patients having vasospastic conditions) (i.e. Buerger’s disease and Reynaud’s phenomenon)
2 classes of NTs of the ANS
Cholinergic (Acetylcholine)
Adrenergic (Phenylethylamine/catecholamine)
Remember to use these classification because sympa not always catecholamine and para not always acetylcholine (i.e. sweat glands are sympa by cholinergic in nature)
Saxitoxin and Tetrodotoxin MOA and function
Blocks Na Channels
Local anaesthetic
Metyrosine MOA and function
Blocks catecholamine synthesis by block tyrosine hydroxylase (try to dop)
Decreases catecholamine in circulation
Reserpine MOA and function
Disrupts NT storage
Depletes catecholamine level to almost 0
Botulinum toxin MOA and function
Prevents release of ACh from the cholinergic vehicle
Causes muscle relaxation
Tyramine, Amphetamine MOA and function
Promotes NE transmitter release
Increased sympathetic effects
Cocaine MOA and function
Inhibits NE, Ser, and Dop reuptake after release
Previously used as anaesthetic
Prolonged sympathetic effects
Bethanecol MOA and function
Activates muscarinic receptor
Smooth muscle stimulant (GIT, urinary)
Atropine MOA and function
Anti-muscarinic
Muscle relaxation
Neostigmine MOA and function
Enzymatic degradation of NT (Anticholinesterase)
Inhibits ACh
