Date | November 2018 | Marks available | 2 | Reference code | 18N.3.SL.TZ0.4 |
Level | Standard level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
Command term | Distinguish | 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.
Using only the data in the table, distinguish between the use of energy in the brain and in skeletal muscle.
Suggest one reason for the difference between the brain and skeletal muscle in metabolic rate.
Outline the role of the brain in involuntary control.
Markscheme
1000 ✔
Working not required
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
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 ✔
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