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Edexcel IGCSE Biology 2.89 Neurotransmitters At Synapses Questions

At a synapse, a nerve impulse triggers neurotransmitter release. The chemical crosses the gap and starts an impulse in the next neurone.

Syllabus
First assessment 2019
Course
Biology 4BI1

Exam points

  • Identify the axon terminals as the part of a neurone where impulses are transferred to an effector.
  • Explain why transmission across additional synapses slows a pathway through neurotransmitter diffusion across synaptic gaps.

Edexcel IGCSE Biology 2.89 Neurotransmitters At Synapses Questions question 1

[Maximum number: 2]

Multiple sclerosis is a condition that can slow down the speed at which electrical impulses travel along neurones.

The time taken for the blink reflex to occur can be used to help diagnose if someone has multiple sclerosis.

The blink reflex causes the eyelid to close.
Air is blown on to the eye and the time taken for the eyelid to close is recorded.
The diagram shows the reflex pathway.

Figure for Question Edexcel IGCSE Biology 2.89 Neurotransmitters At Synapses Questions question 1 — Edexcel IGCSE Biology

The speed the impulse moves along the reflex arc consisting of all three neurones in a person without multiple sclerosis is 77 metres per second.

The time taken for the blink reflex to occur in a person with multiple sclerosis is 0.0050 s .

The total length of the neurones in the reflex arc for the person with multiple sclerosis is 25 cm .

The speed of an impulse along the axon of the motor neurone for someone without multiple sclerosis is 120 metres per second.

Suggest why the speed of the impulse calculated along all three neurones is less than the speed of the impulse along only the motor neurone.

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