deck_762233 Flashcards
Where is acetylcholine released in the nervous sytem?
Parasympathetic nervous systema) Pre ganglionic neuronesb) Post ganglionic neuronesSympathetic Nervous Systema) Pre ganglion neuronesb) Some post ganglionic neurones (sweat, ejaculation)
What is acetylcholine synthesized from and how?
Choline and Acetyl Co-A, via the action of choline acetyltranferase.
Where does acetylcholine synthesis take place? What enzyme is produced and how does it get to the nerve terminals?
Acetycholine synthesized in cholnergic neurones.Choline acetyltransferase made in cell bodies of cholinergic neurones.. Transferred to the nerve terminal by axoplasmic transport.
How is acetylcholine packaged for release?
Acetylcholine packed into vesicles and travels to the nerve endings via anteretrograde (movement away from cell body) axoplasmic transport. Stored at nerve ending until action potential arrives.
What is the vesicular ACh transporter?
Carrier protein on surface of vesicle in which ACh is absorbed. Actively transport one molecule ACh into vesicle in exchange for two cytoplasmic protons. Example of antiport.
How is ACh released from axon terminal?
- Action potential arrives- Depolarisation causes voltage gates Ca2+ channels to open- Calcium ions diffuse through down their concentration gradient- Ca2+ binds to synaptotagmin - a membrane trafficking protein- Vesicle brought close to membrane- Snare complex makes a fusion pore- Transmitter released through pore
Give an example of an agent which interferes with ACh release
Botulinum toxin- Taken into neurones by endocytosis- Has protease activity, cleaves SNARE complex and prevents neurosecretory vesicle from fusing with nerve synapse.
How is acetylcholine degraded?
Acetylcholinesterase Abundant enzyme which converts acetylcholine into the inactive metabolies choline and acetate
What happens to the free Choline and Acetate in the synapse?
Choline - transported back into the neurone by a high affinity choline transporter on the membraneAcetate- Converted into acetyle CoA and reused to make ACh by choline acetyltransferase
List some of the important sites of parasympathetic innervation
Innervation of the heartBronchiolesVasculaturePupil of the eyeEndocrine glands
Wjhat is the effect of increased parasympathetic discharge in the heart?
Decrease heart rate (AVN conduction velocity),
Apart from in the parasympathetic system, where else is acetylcholine used in the body?
Preganglioncic in the sympathetic nervouse systemPostganglionic in some part of the sympathetic nervous system, notable to sweat glands (M3)
What are two types of acetylcholine receptors?
Nicotinic and mucarinic
Why are the two types of acetycholine receptors distinguishable?
Muscarinic receptors more sensitive to muscarineNicotinic more responsive to… that’s right, you guessed it! Heroin.Lol, JK. Nicotine.
How do nicotinic acetylcholine receptors cause a post ganglionic response?
- Ligand gated ion channel - Channel permeable to Na+ and K+, causes depolarisation (local, immediate)- Action potential propagatesNicotIONe
How do muscarinic acetylcholine receptors cause a post ganglionic response?
- G-protein coupled receptor- G-protein diffuse to membrane protein- Cascade reaction- Signal propagated to whole of cell- Slow response
What is the class of acetylcholine receptor found at the neuroeffector junction?
Muscarinic