DP Biology (first assessment 2025)

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Question 23M.2.SL.TZ1.8

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Date May 2023 Marks available [Maximum mark: 6] Reference code 23M.2.SL.TZ1.8
Level SL Paper 2 Time zone TZ1
Command term Explain Question number 8 Adapted from N/A
8.
[Maximum mark: 6]
23M.2.SL.TZ1.8

Explain how breathing is controlled by the brain.

[6]

Markscheme
  1. breathing is an automatic process/can occur without conscious intervention/is involuntary/ autonomic;
  2. voluntary/conscious factors can override automatic functions (for a limited time);
  3. control of the breathing comes from the respiratory centre;
  4. (respiratory centre) located in the medulla of the brain;
  5. exercise results in higher CO2 levels in blood;
  6. breathing rate changes in response changes to blood pH/acidity/CO2 level;
  7. medulla contains chemoreceptors
    OR
    chemoreptors in aortic/carotid bodies send signals to medulla;
  8. respiratory centre/medulla sends nerve impulses to diaphragm/intercostal muscles;
  9. stimulates (the intercostal muscles/diaphragm) to control breathing rate/depth of inspiration/contraction;

Syllabus sections