The diagram below shows the structure of the retina. Label I and II.

Label I and II.

Distinguish between rods and cones.

Outline the pupil reflex.

Discuss the use of the pupil reflex in testing for brain death.

I: ganglion cell
II: bipolar cell/neuron

(both needed)

I: lacteal
II: longitudinal/smooth muscles / muscularis mucosa

(both needed)

To award [2 max] responses need to be compared.
Responses do not need to be shown in a table format.

rapid unconscious response to change in light intensity / controls amount of light entering eye to prevent damage to retina/to see in darkness;
in bright light circular muscles in iris contract causing pupil to constrict / in dim light longitudinal/radial muscles in iris contract causing pupil dilation;
constriction by parasympathetic NS / dilation by action of sympathetic NS;

pupil reflex is a brain stem reflex / shows activity in the medulla oblongata;
pupil reflex must be absent in brain death;
pupil reflex is possible in coma victims where motor function is absent;
pupil reflex alone not enough to diagnose brain death;
other criteria include coma/absence of response to pain in all extremities/ absence of brain stem reflexes/lack of respiratory movements;
some cases of coma irreversible / some cases may recover;
doctors need to diagnose damage to decide treatment/long-term life support /organ donation;

Good answers.

Very few identified the muscle correctly. There was some complaint about the fact that what was tested was a longitudinal section of the villus instead of a transverse section as stated in the guide. The complaint is reasonable, nevertheless, the candidates should have known the order in which the muscle layers appear and could have inferred the answer to the question. As a matter of fact, the more able candidates answered this question correctly.

Good answers.

Several answers described the pupil reflex arc/pathway which was sometimes sufficient to gain one mark.

Few answers related to coma victims, dismissing almost half of the possible marking points but leaving sufficient possibilities to score well. Many candidates considered that if no pupil reflex is present, brain death is sure. Some stated the role of brain stem. Vegetative state was confounded with brain death. Several candidates repeated part of the information given in the previous question.