Photoreception in rod cellsEdexcel International A Level Biology: Mind map

Exam questions on Photoreception in rod cells

1. A vision scientist is recording the membrane potential of a single rod cell taken from the retina of a dark-adapted animal. She records first in complete darkness and then when a brief flash of light is delivered.
   Describe what happens to rhodopsin when a rod cell absorbs light.2 marks
2. In a further experiment the scientist exposes a dark-adapted rod cell to a dim flash of light and measures changes in the rod cell and in the bipolar neurone that it synapses with.
   Explain why absorption of light causes the rod cell membrane to become hyperpolarised.2 marks
3. A driver leaves a brightly lit road tunnel and enters a poorly lit country lane at night. For several minutes she can see almost nothing, but her vision then slowly improves.
   Describe how absorption of light by rod cells in the driver's retina leads to an action potential in an optic neurone.3 marks