Date | May 2015 | Marks available | 1 | Reference code | 15M.3.HL.TZ1.5 |
Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
Command term | State | Question number | 5 | Adapted from | N/A |
Question
Label the numbered parts of the reflex arc.
State the type of human sensory receptor that detects motion, gravity and stretch.
State the part of the brain responsible for coordination and balance, especially during athletic competition such as the Olympics.
Outline control of heart rate by the medulla oblongata.
Markscheme
Award [1] for every two correct up to [2 max].
I: sensory/afferent neuron;
II: interneuron/relay neuron;
III: motor/efferent neuron;
IV: effector/muscle;
mechanoreceptor
cerebellum
a. (autonomic nerve signals from medulla oblongata) can override pacemaker;
b. parasympathetic stimulation decreases heart rate;
c. parasympathetic/vagus nerve runs from the medulla oblongata to the heart;
d. sympathetic nerves from medulla (travel down spinal cord where) synapse with other nerves before going to heart;
Examiners report
The majority of candidates were able to correctly label the reflex arc.
Almost all could name mechanoreceptors.
The majority correctly identified the cerebellum although occasionally cerebrum or brain stem was chosen, not earning a mark.
Few candidates gained more than 1 mark and many did not score any. The role of the medulla oblongata in modifying the innate rhythm of the pacemaker was not understood. Parasympathetic control and the role of vagus nerve were not often mentioned. Candidates frequently talked about flight-or-fight responses and the role of adrenaline instead. Another misconception was that the medulla oblongata actually was initiating each heart beat rather than overriding the SAN. This section seemed to be poorly taught.