Autonomic nervous system 2 Flashcards
What can happen to neurotransmitter in the pre-synaptic neurone?
Packaged into vesicles waiting to be released
Degraded
What can happen to neurotransmitter after it has been released into the synaptic cleft?
Diffuses across synaptic cleft
binds to receptors on post-synaptic membrane
Inactivated by enzymes
breakdown products taken up by pre-synaptic neuurone
Binds to receptors on pre-synaptic membrane
Taken up by pre-synaptic neurone
What is the reaction of acetylcholine synthesis?
Acetyl coA + choline —–> acetylcholine + coA
What enzyme catalyses the reaction
Acetyl coA + choline —–> acetylcholine + coA
Choline acetyl transferase
What is the reaction of acetylcholine degradation?
Acetylcholine —–> acetate + choline
What enzyme catalyses the reaction
Acetylcholine —–> acetate + choline
Acetylcholinesterase
How varied are nicotinic acetylcholine receptors?
Different nictonic acetylcholine receptors at autonomic nerve fibres ganglia and at neuromuscular junctions
What are ganglion-blocking drugs?
Drugs that block nicotinic acetylcholine receptors specifically at autonomic nerve fibres ganglia
How specific are muscarinic acetylcholine receptor agonists and antagonists?
Not very specific to the receptor subtypes M1, M2, M3 etc.
affect all of them
What are the consequences of muscarinic acetylcholine receptor agonists not being specific?
Decreased heart rate
Bronchoconstriction
SLUDGE
What does SLUDGE stand for?
Salivation
Lacrimation - eyes tearing up
Urination
Defecation
GI upset
Emesis - vomiting
How is SLUDGE treated?
Muscarinic acetylcholine receptor antagonists
What are the effects of acetylcholinesterase inhibitors?
Raise acetylcholine levels
enhance stimulation of muscarinic acetylcholine receptors
What is the structure of sympathetic post-ganglionic neurons?
Axons are branched
lots of varicosities
What is a varicosity?
Bulging of the axon
where synapses can form
What is the starting molecule of noradrenaline synthesis?
Tyrosine
What are the intermediate molecules of noradrenaline synthesis?
DOPA
Dopamine
What catalyses the reaction
Tyrosine —–> DOPA?
Tyrosine hydroxylase
What catalyses the reaction
DOPA —–> Dopamine
DOPA decarboxylase
What catalyses the reaction
Dopamine —–> noradrenaline?
Dopamine B-hydroxylase
Where does the reaction
Noradrenaline —–> adrenaline occur?
Adrenal medulla chromaffin cells
What catalyses the reaction
Noradrenaline —–> adrenaline?
N-methyltransferase
How is noradrenaline signalling in synapses terminated?
Noradrenaline is transported into the pre-synaptic neurone
What are the different mechanisms of noradrenaline transport into the pre-synaptic neurone?
Uptake 1 - symporter moves noradrenaline along with sodium ions into pre-synaptic neurone
Uptake 2
Which mechanism is largely responsible for noradrenaline transport into the pre-synaptic neurone
Uptake 1
How is noradrenaline that’s not packaged into vesicles degraded?
Broken down by enzymes
What enzyme breaks down noradrenaline?
Monoamine oxidase
How specific are adrenoceptor agonists and antagonists?
Specific to the receptor subtype A1, A2, B1, B2 etc.