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Give two reasons why transmission across a cholinergic synapse is unidirectional - AQA - A-Level Biology - Question 7 - 2022 - Paper 1
Question 7
Give two reasons why transmission across a cholinergic synapse is unidirectional. 1. Only the presynaptic neurone has neurotransmitter acetylcholine. 2. Only the pos... show full transcript
Worked Solution & Example Answer:Give two reasons why transmission across a cholinergic synapse is unidirectional - AQA - A-Level Biology - Question 7 - 2022 - Paper 1
Step 1
Step 2
Name and explain the type of summation shown in Figure 4.
Answer
Type of summation: Temporal. Explanation: This type of summation occurs when several repeated impulses arrive in a short time, allowing sufficient acetylcholine to accumulate and reach the threshold potential to initiate an action potential.
Step 3
Suggest and explain how MG can weaken contraction of muscles.
Answer
- Less/no acetylcholine binds to the receptors on the postsynaptic membrane.
- This lack of binding results in less depolarisation, preventing the generation of action potentials and consequently reducing muscle contraction.
Step 4
Mestinon can help in the treatment of MG. Explain how.
Answer
- Mestinon inhibits the enzyme that breaks down acetylcholine, allowing more of it to remain available in the synaptic cleft.
- This increased presence of acetylcholine means more can attach to receptors on the postsynaptic membrane.
- As a result, it enhances depolarisation, promoting action potentials and improving muscle contraction.