Lecture 10 - The Autonomic Nervous System; Pharmacokinetics Flashcards
what comprises the autonomic nervous system?
series of 2 neurones - pre and post ganglionic
where do cell bodies lie in the ans?
one in the cns, one in the pns
how do neurones exert actions?
via smooth muscle, viscera and secretory glands
describe the thoraco-lumbar outflow
nerve fibres have cell bodies in T1-L2 (14 sections)
short pre ganglionic, long post ganglionic
where can thoraco-lumbar outflow synapse?
same level to origin
different level to origin
not in paravertebral chain
what is the neurotransmission of pre ganglionic neurones in thoraco-lumbar outflow?
cholinergic
what is the neurotransmission of post ganglionic neurones in thoraco-lumbar outflow?
noradrenergic
describe the cranio-sacral outflow
long pre ganglionic
short post ganglionic
what is the neurotransmission of pre ganglionic neurones in cranio-sacral outflow?
cholinergic
what is the neurotransmission of post ganglionic neurones in cranio-sacral outflow?
cholinergic
how is acetylcholine synthesised?
from choline and acetyl CoA with choline acetyltransferase
how is ACh tranported into synaptic vesicles?
indirect active transport mechanism
how does the activity of acetylcholinesterase change at fast cholinergic synapses?
activity is higher
how is noradrenaline synthesised and what is the rate limiting enzyme?
from tyrosine within the nerve terminal
tyrosine hydroxylase
what is the role of dopamine beta-hydroxylase?
transports newly synthesised dopamine into vesicle prior to conversion to noradrenaline
what breaks down cytoplasmic noradrenaline?
monoamine oxidase
what is the pathway from tyrosine to noradrenaline?
tyrosine -> dopa -> dopamine -> noradrenaline
how is noradrenaline released?
calcium mediated exocytosis
what is the ‘uptake 1’ system?
high affinity reuptake
rapidly removes na from synaptic cleft
rapidly decreases localised concentration and terminating actions
what is the ‘uptake 2’ system?
widespread, low affinity reuptake
extra na is removed from the extracellular space
how is ACh and na release regulated?
triggered by depolarisation of nerve terminal membrane, Ca entry and fusion of vesicles with presynaptic membrane
what are the major drug classes that affect autonomic nervous system function?
nicotinic cholinoceptor antagonists
muscarinic cholinoceptor agonists
muscarinic cholinoceptor antagonists
8cholinesterase inhibitors
how do cholinoceptor ant/agonists interfere with cholinergic transmission?
interact with cholinoceptors
how do cholinesterases interfere with cholinergic transmission?
decrease rate of degradation of ACh so prolong lifetime in the cleft
what is an example of a nicotinic cholinoceptor antagonist?
tubocurarine