The eye, rods and pupil responsesEdexcel A-Level Biology A: Flashcards
What these 13 flashcards ask
- What is a reflex?
- Give the pathway of the pupil reflex.
- What do the circular muscles of the iris do in bright light?
- What do the radial muscles of the iris do in dim light?
- Why are the circular and radial muscles described as antagonistic?
- Why does the pupil constrict in bright light?
- What is rhodopsin made of?
- What happens to rhodopsin when it absorbs light?
- What is the state of a rod cell's cation channels in the dark?
- What does a rod cell do in the dark that affects the bipolar neurone?
- What happens to cation channels when rhodopsin splits?
- What is hyperpolarisation?
- How does a hyperpolarised rod lead to an action potential in the optic neurone?
Exam questions on The eye, rods and pupil responses
- An ophthalmologist shines a bright light into one eye of each of two patients and watches the pupil. In the first patient the pupil constricts quickly. In the second patient, the motor neurones that supply the iris muscles have been damaged by a head injury, and the pupil does not constrict.Explain why the pupil of the second patient does not constrict.2 marks
- A driver leaves a brightly lit petrol station and pulls onto an unlit country road at night. For the first few minutes she cannot see the road edge clearly, but her vision gradually improves.Explain why the driver cannot see clearly at first on the dark road.2 marks
- Vitamin A is needed to make retinal. A man whose diet is deficient in vitamin A has difficulty seeing in dim light, a condition called night blindness. His rod cells contain less rhodopsin than normal.Explain why the man's lack of vitamin A makes it difficult to detect dim light.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).