synaptic transmission

Question 1

transmission across cholinergic synapse - pre synaptic neurone

Answer 1

depolarisation of pre synaptic membrane - opening of calcium ion channels
calcium ions diffuse into pre synaptic neurone
causing vesicles containing ach to move and fused with pre synaptic membrane
release acc into synaptic cleft via exocytosis

Question 2

transmission across cholinergic synapse
post synaptic neurone

Answer 2

ach diffuse across synaptic cleft
bind to specific receptors on post synaptic membrane
causing na channels to open
na diffuse into post synaptic knob causing depolarisation
threshold met - ap initiated

Question 3

what’s happens to ach after synaptic transmission

Answer 3

hydrolysed by acetylcholinersterase
products reabsorbed by pre synaptic neurone
to stop overstimulation
as if not removed it would keep binding to receptors causing depolarisation

Question 4

how do synapse result in unidirectional nerve impulse

Answer 4

NT only made in or released from pre synaptic neurone
receptors only on post synaptic neurone

Question 5

summation by synapses

Answer 5

addition of number of impules
converging on single post syntactic neurone
causing rapid build of nt
so threshold more likely to be reached and AP generated

Question 6

spatial summation

Answer 6

many pre synaptic neurones share one synaptic cleft and post synaptic neurone
collective release sufficient NT to reah threshold and trigger AP

Question 7

temporal summation

Answer 7

one pre synaptic neurone release nt many times over short time
suffiecnt nt to reach threshold trigger AP

Question 8

inhibition by inhibitory synapse

Answer 8

inhibitory NT hyperpolarise post synaptic membrane
cl channels open and cl diffuse in
k channels open and k diffuse out
more na is therefore required for depolarisation
reducing likelyhood of threshold being met and an AP forming at post synaptic membrane

Question 9

structure of nmj

Answer 9

receptors are on muscle fibre instead of postsynaptic membrane
muscle fibres - form clefs - store enzymes eg acetylcholinesterase to break down NT

Question 10

compare transmission across cholinergic synapse and neuromuscular junctions

Answer 10

both - transmission is unidirectional
cholinergic is neurone to neurone vs NMJ is neurone to muscle
cholinergic nt can be excitatory or inhibitory but NMJ always excitatory
cholinergic AP may be initiated in post synaptic neurone but in NMJ AP propagates along sarcomella down t tubules

Question 11

effects of drugs on synapse

Answer 11

Some drugs stimulate the nervous system, leading to more action potentials
○ Similar shape to neurotransmitter
○ Stimulate release of more neurotransmitter
○ Inhibit enzyme that breaks down neurotransmitter → Na+ continues to enter
● Some drugs inhibit the nervous system, leading to fewer action potentials,
○ Inhibit release of neurotransmitter eg. prevent opening of calcium ion channels
○ Block receptors by mimicking shape of neurotransmitter