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Date November 2018 Marks available 1 Reference code 18N.3.SL.TZ0.4
Level Standard level Paper Paper 3 Time zone TZ0 / no time zone
Command term Calculate Question number 4 Adapted from N/A

Question

The energy used by the brain and skeletal muscle of a 70 kg man was measured over the period of one day.

The metabolic rate is the energy used per kilogram of mass per day. Calculate the metabolic rate of the brain.

[1]
a.

Using only the data in the table, distinguish between the use of energy in the brain and in skeletal muscle.

[2]
b.

Suggest one reason for the difference between the brain and skeletal muscle in metabolic rate.

[1]
c.

Outline the role of the brain in involuntary control.

[2]
d.

Markscheme

1000 ✔

Working not required

a.

a. skeletal muscle uses more total energy than the brain ✔

b. the brain uses more energy per kg than skeletal muscle
OR
the brain has higher metabolic rate ✔

 

Accept numerical answers if comparative terms are used

b.

a. «brain requires more» energy to maintain a proper ionic balance/homeostasis/active transport ✔

b. «brain requires more» energy for synapses/neurotransmitters ✔

c. «brain requires more» energy for thinking and memory ✔

d. skeletal muscle active on demand but brain constantly active ✔

c.

a. does not require conscious thought ✔

b. can respond to emergency situation and «actively» return the body to normal ✔

c. medulla/brain stem controls involuntary activities ✔

d. eg: swallowing/breathing/heart rate ✔

 

Accept other valid examples

d.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.

Syllabus sections

Option A: Neurobiology and behaviour » Option A: Neurobiology and behaviour (Core topics) » A.2 The human brain
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Option A: Neurobiology and behaviour » Option A: Neurobiology and behaviour (Core topics)
Option A: Neurobiology and behaviour

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