1. Give two reasons why transmission across a cholinergic synapse is unidirectional - AQA - A-Level Biology - Question 7 - 2022 - Paper 1
Question 7
1. Give two reasons why transmission across a cholinergic synapse is unidirectional.
1 Only the presynaptic neurone releases acetylcholine.
2 The postsynaptic ... show full transcript
Worked Solution & Example Answer:1. Give two reasons why transmission across a cholinergic synapse is unidirectional - AQA - A-Level Biology - Question 7 - 2022 - Paper 1
Step 1
Give two reasons why transmission across a cholinergic synapse is unidirectional.
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Answer
Only the presynaptic neurone releases acetylcholine.
The postsynaptic neurone has receptors that respond to the neurotransmitter.
Step 2
Name and explain the type of summation shown in Figure 4.
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Answer
Type of summation: Temporal
Explanation: Temporal summation occurs when several repeated impulses in a short time provide enough neurotransmitter (acetylcholine) to reach the threshold potential.
Step 3
Suggest and explain how MG can weaken contraction of muscles.
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Answer
Myasthenia Gravis (MG) can lead to weakened muscle contraction due to the following reasons:
Fewer or no acetylcholine molecules are able to bind to receptors on the muscle cell surface, which diminishes the likelihood of action potentials being generated. As a result, the muscle fails to contract effectively.
Step 4
Mestinon can help in the treatment of MG. Explain how.
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Answer
Mestinon helps treat MG by inhibiting the breakdown of acetylcholine at the neuromuscular junction. This results in more acetylcholine remaining at the synapse, allowing for increased stimulation of muscle receptors, leading to better muscle contraction.
