5.4

Question 1

When 2 neurones meet, there is a tiny gap between them called a

Answer 1

synaptic cleft

Question 2

the point where the 2 neurones meet is called a

Answer 2

synapse

Question 3

the end of the axon of the presynaptic neurone is swollen to form a

Answer 3

synaptic knob - contains many vesicles containing a neurotransmitter

Question 4

neurotransmitter =

Answer 4

acetylcholine

Question 5

synapses that use acetylcholine are called

Answer 5

cholinergic synapses

Question 6

there is a synaptic cleft between the synaptic knob and the membrane of the

Answer 6

post-synaptic neurone

Question 7

the membrane of the post-synaptic neurone has many

Answer 7

sodium channels

Question 8

impulses are passed across the synaptic cleft by the

Answer 8

neurotransmitter

Question 9

1) An AP arrives in the presynaptic neurone, causes calcium channels to open and

Answer 9

calcium ions enter the synaptic knob

Question 10

2) calcium ions cause the vesicles of acetylcholine to fuse with the presynaptic membrane - acetylcholine is released into the

Answer 10

synaptic cleft and diffuses across to the postsynaptic membrane

Question 11

3) Acetylcholine binds to specific receptor sites on the sodium channels in the postsynaptic membrane. This causes the sodium channels to open -

Answer 11

allowing sodium ions to enter the post-synaptic neurone

Question 12

4) if enough sodium ions enter to overcome the threshold value, an AP is generated in the

Answer 12

postsynaptic neurone

Question 13

5) acetylcholinesterase (an enzyme in the synaptic cleft). the breakdown products diffuse back across the cleft and back into the synaptic knob -

Answer 13

the sodium channels close once the acetylcholine is broken down

Question 14

6) ATP produced in the mitochondria is used to re-form acetylcholine from the breakdown products. This is stored in vesicles in the

Answer 14

synaptic knob until it is needed again