Cholinergic Synnapses
Biology: Cambridge International A Level, topic 15.1.8
Cholinergic Synapses
Synapses that use acetylcholine as a neurotransmitter are called cholinergic synapses. Although acetylcholine is also used at a neuromuscular junction, there are some key differences:
Types of postsynaptic cell
- Cholinergic synapses are between two neurones.
- Neuromuscular junctions are between a motor neurone and a muscle cell.
Number of receptors
- There are less receptors in the postsynaptic membrane at a cholinergic synapse than at a neuromuscular junction.
Type of response
- A cholinergic synapse can trigger an inhibitory or excitatory response in the postsynaptic membrane.
- An action potential at a neuromuscular junction always triggers an excitatory response in the muscle cell.
Result of depolarisation
- In a cholinergic synapse, depolarisation of the postsynaptic membrane results in an action potential.
- At a neuromuscular junction, depolarisation of the postsynaptic membrane results in muscle contraction.
Acetylcholinesterase
- Acetylcholinesterase is the enzyme that breaks down acetylcholine after it has bound to the receptors on the postsynaptic membrane.
- In cholinergic synapses, the enzyme is located in the synaptic cleft.
- At a neuromuscular junction, the enzyme is stored in clefts in the postsynaptic membrane.
Test yourself on Cholinergic Synnapses
What are the differences between neuromuscular junctions and cholinergic synapses?
Which of the following statements about cholinergic synapses are true?
Where is acetylcholinesterase stored in a neuromuscular junction?