Module 5: Cholinergic Synapse

Question 1

A synapse is …

Impulses are transmitted across the synapse using chemicals called …

Answer 1

the junction between 2 neurones

neurotransmitters

Question 2

Neurotransmitters can either be …

Answer 2

excitatory or inhibitory

Question 3

What do excitatory neurotransmitters result in ?
Describe what effect this has on generation of an action potential

Answer 3

the depolarisation of the post synaptic neurone , if threshold is reached this triggers an action potential in the post synaptic neurone

Question 4

What do inhibitory neurotransmitters result in?
Describe what effect this has on generation of an action potential

Answer 4

the hyperpolarisation of the post synaptic membrane which prevents an action potential being generated

Question 5

Using the cholinergic synapse as an example , describe the first 2 steps of synaptic transmission.

Answer 5

1)an action potential reaches the axon terminal of the presynaptic neurone
2)the action potential triggers the opening of voltage gated calcium ion channels , therefore calcium ions diffuse into the presynaptic neurone

Question 6

Name the specific voltage gated ion channel involved in cholinergic synapses

Answer 6

voltage gated calcium ion channels

Question 7

Describe the next 2 steps of synaptic transmission at a cholinergic synapse

Answer 7

3)influx of calcium ions causes vesicles to move forwards and fuse with the presynaptic membrane , acetylcholine is then released from vesicles and leaves the neurone by exocytosis
4)acetylcholine binds to receptors on the receptor gated sodium ion channels causing them to open , so sodium ions diffuse into postsynaptic neurone down their EC gradient

Question 8

Name the specific neurotransmitter that is involved in cholinergic synpases

Answer 8

acetylcholine

Question 9

Describe the final 2 steps of synaptic transmission at a cholinergic synapse

Answer 9

5)influx of sodium ions causes generation of another action potential in the postsynaptic neurone
6)any remaining acetylcholine in the synaptic cleft is broken down by acetylcholinesterase into acetic acid and choline so that its more easily absorbed by the presynaptic neurone

Question 10

Name the enzyme used to break down acetylcholine
What is formed by this reaction?

Answer 10

acetylcholinesterase

acetic acid and choline