DP Biology (last assessment 2024)

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Question 23M.3.SL.TZ1.19

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Date May 2023 Marks available [Maximum mark: 4] Reference code 23M.3.SL.TZ1.19
Level SL Paper 3 Time zone TZ1
Command term Explain Question number 19 Adapted from N/A
19.
[Maximum mark: 4]
23M.3.SL.TZ1.19

Ventricular contraction is coordinated to pump as much blood as possible into the arteries. Explain how this is achieved.

[4]

Markscheme
  1. impulses initiate in SAN/pacemaker;
  2. impulses transmitted to AV node;
  3. AV node transmits impulses to ventricles;
  4. delay before ventricles contract;
  5. ventricular contraction/systole begins from the base/apex;
  6. ensures ventricles are completely emptied;
  7. fibres ensure both ventricles contract together;
  8. AV valves close during ventricular systole/contraction
    OR
    AV valves close to prevent backflow of blood to atria;

In mpg, accept Purkinje fibres or bundle of His

Examiners report

Most candidates mentioned SA and AV nodes and the delay and this appeared well understood. Some weaker answers focussed on the cardiac cycle or pressure changes.