Cholinergic Synapses (AQA A Level Biology)

Cholinergic Synapses

• Where two neurones meet, they do not actually come into physical contact with each other – a very small gap, known as the synaptic cleft, separates them

• The ends of the two neurones, along with the synaptic cleft, form a synapse

A synapse

Synaptic transmission

• Electrical impulses cannot ‘jump’ across synapses

• When an electrical impulse arrives at the end of the axon on the presynaptic neurone, chemical messengers called neurotransmitters are released from vesicles at the presynaptic membrane

• The neurotransmitters diffuse across the synaptic cleft and temporarily bind with receptor molecules on the postsynaptic membrane

• This stimulates the postsynaptic neurone to generate an electrical impulse that then travels down the axon of the postsynaptic neurone

• The neurotransmitters are then destroyed or recycled to prevent continued stimulation of the second neurone, which could cause repeated impulses to be sent

• Synapses that use acetylcholine as a neurotransmitter are described as cholinergic synapses