DP Biology (first assessment 2025)

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Question 19N.2.SL.TZ0.c

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Date November 2019 Marks available [Maximum mark: 7] Reference code 19N.2.SL.TZ0.c
Level SL Paper 2 Time zone TZ0
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 7]
19N.2.SL.TZ0.c

Explain the control mechanism of the heart rate.

[7]

Markscheme

a. sinoatrial node/SAN is a specialized group of muscle cells
OR
sinoatrial node/SAN is located in the right atrium ✔

b. acts as a pacemaker/controls the heart rate
OR
initiates/generates the heart beat/starts the cardiac cycle ✔

c. sends out electrical signal/impulses/depolarisations ✔

d. electrical signal stimulates contraction «of heart muscle» ✔

e. signal passes through walls of atria/passes to AV node ✔

f. then through walls of the ventricles ✔

g. medulla «oblongata of brain» can change/increase/decrease the rate ✔

h. through nerves/named example of nerve/autonomic/sympathetic/ parasympathetic nervous system ✔ In mph, only accept vagus nerve for slowing heart rate and sympathetic nerve for accelerating it.

i. one nerve increases the rate and the other decreases it ✔

j. epinephrine/adrenaline increases heart rate/force of contraction ✔

k. epinephrine/adrenaline prepares the body for vigorous activity/is part of fight or flight response ✔

Syllabus sections