Inhibitory Synapses (A-level Biology)
Inhibitory Synapses
Excitatory and Inhibitory Synapses
- Excitatory neurotransmitters make an action potential more likely to fire by depolarising the post-synaptic membrane.
- Inhibitory neurotransmitters make an action potential less likely to fire by hyperpolarising the post-synaptic membrane.
Role of Acetylcholinesterase
- Acetylcholine must be removed from the synaptic cleft or it would continually initiate new action potentials. This means the impulses would not be distinct.
- Acetylcholinesterase is the enzyme that hydrolyses acetylcholine. The products of this reaction are re-absorbed into the pre-synaptic neurone.
- Acetylcholine can be an inhibitory or an excitatory neurotransmitter depending on where the cholinergic synapse is:
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- It acts as an excitatory neurotransmitter at synapses in the central nervous system. It depolarises the post-synaptic membrane by opening sodium ion channels.
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- It can also act as an inhibitory neurotransmitter at synapses in the heart. It hyperpolarises the post-synaptic membrane by opening potassium ion channels.
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