Transmission across synapses

Question 1

How do neurotransmitters reach the presynaptic membrane?

Answer 1

1. the action potential reaches the end of the presynaptic neurone
2. depolarisation of the presynaptic membrane causes calcium ion channels to open
3. calcium ions diffuse into the presynaptic knob
   
   1. this cause synaptic vesicles contrianing neurotransmitter to fuse with the presynaptic membrane

Question 2

How is an action potential triggered in the postsynaptic neurone?

Answer 2

1. neurotransmitter is released into the synaptic cleft by exocytosis
2. it diffuses across the synaptic cleft and binds with its specific receptor molecule on the postsynaptic membrane
3. this causes sodium ion channels to open
4. sodium ions diffuse into the postsynaptic neurone
   
   1. this triggeres an action potetial and the impulse is propagated along the postsynaptic neurone

Question 3

How is the acetycholine removed from the receptors on the postsynaptic membrane?

Answer 3

acetycholine is broken down by enzymes, which also released them from receptors on the postsynaptic mebrane

the products are taken back into the presynaptic knob

Question 4

Why is it important to remove any neurotransmitter from the postsynaptic membrane?

Answer 4

so the stimulus is not maintained

so another stimulus can arrive at and affect the synapse

also allows some neurotransmitter to be recycled

Question 5

What type of neurotransmitter does cholinergic synapse use?

Answer 5

acetylcholine

cholinergic

relating to or denoting nerve cells in which acetylcholine acts as a neurotransmitter.

Question 6

Where are these synapses found?

Answer 6

in the CNA of vertabreates and at neuromuscular junctions (where a motor neurone and a mucle cell meet)

Question 7

What happens after acetycholine triggers an action potential?

Answer 7

acetycholine is hydrolysed by a specific enzyme - acetylcholinesterase

this enzyme is situated on the postsynaptic membrane

Question 8

Whaat are the products of the break down of acetylcholine?

Answer 8

hydrolysed to give choline and ethanoic acid

Question 9

What happens with the products?

Answer 9

taken back into the presynaptic knob to be reformed into acetylcholine