When a nerve impulse arrives at a synapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob - AQA - A-Level Biology - Question 1 - 2017 - Paper 1
Question 1
When a nerve impulse arrives at a synapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob.
Describe how.
Worked Solution & Example Answer:When a nerve impulse arrives at a synapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob - AQA - A-Level Biology - Question 1 - 2017 - Paper 1
Step 1
Nerve Impulse Arrival
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Answer
When a nerve impulse is received, it causes the depolarization of the presynaptic membrane. This change in voltage triggers specific proteins called voltage-gated calcium channels to open.
Step 2
Calcium Influx
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Answer
As a result of the channel opening, calcium ions (Ca2+) enter the presynaptic knob through facilitated diffusion.
Step 3
Vesicle Fusion
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Answer
The influx of Ca2+ ions causes synaptic vesicles containing neurotransmitters to fuse with the presynaptic membrane, leading to the release of neurotransmitter into the synaptic cleft.
