The Role of Synapses 5.3.8

Question 1

What is a synapse?

Answer 1

The junction where two neurones meet

Question 2

What does a synapse consist of?

Answer 2

A presynaptic knob, synaptic cleft, and a postsynaptic membrane

Question 3

What are cholinergic synapses?

Answer 3

Synapses that use acetylcholine as a neurotransmitter

Question 4

Describe the steps of transmission at a synapse

Answer 4

1. Electrical impulses cannot ‘jump’ across synapses
2. When an electrical impulse arrives at the end of the axon on the presynaptic neurone (also called the synaptic knob), neurotransmitters are released from vesicles at the presynaptic membrane
3. Neurotransmitters diffuse across the synaptic cleft and temporarily bind with receptor molecules on the postsynaptic neurone
4. This stimulates the postsynaptic neurone to generate an action potential that then travels down the axon
5. The neurotransmitters are then recycled by acetylcholinerase to prevent continued stimulation of the second neurone

Question 5

How is acetylcholine released from the presynaptic neurone?

Answer 5

Vesicles release the neurotransmitter by exocytosis