DP Biology (first assessment 2025)

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Question 22M.2.SL.TZ1.5d

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Date May 2022 Marks available [Maximum mark: 3] Reference code 22M.2.SL.TZ1.5d
Level SL Paper 2 Time zone TZ1
Command term Explain Question number d Adapted from N/A
d.
[Maximum mark: 3]
22M.2.SL.TZ1.5d
(d)

Explain how a nerve impulse is passed on to other neurons.

[3]

Markscheme
  1. impulses pass to another neuron at a synapse/across synaptic gap/cleft;
  2. (depolarization causes) Ca2+/calcium ions to diffuse into the (presynaptic) neuron/axon;
  3. depolarization (of presynaptic neuron) causes release of a neurotransmitter
    OR
    neurotransmitters diffuse across the synapse;
  4. (neurotransmitters) bind to receptors on postsynaptic neuron/membrane;
  5. (if the threshold potential is reached) an action potential occurs/sodium gates open (in the postsynaptic neuron);
Examiners report

Use of term "synapse" was often missing; involvement of the brain was sometimes built into the passage of a nerve impulse to another neuron.

Syllabus sections