The Eye (8.5)

Question 1

State the order of neurons involved in responding to light and communicating to the brain, starting with rod cells

Answer 1

Multiple rod cells connect to bipolar cells which are connected to a singualr ganglion cell. This ganglion cell feeds impulses to the optic nerve which is ultimately connected to the CNS

Question 2

Describe the response of rod cells to the dark

Answer 2

1) Sodium diffuses out of inner segment creating conc gradient
2) So sodium drawn from outer segment and sodium channels open so sodium also diffuses back into rod cells.
3) This stimulates the release of glutamate, an inhibitory neurotransmitter
4) Prescence of glutamate prevents impulse being passed onto bipolar cells, so no action potential

Question 3

Describe the response of rod cells to light

Answer 3

1) Prescence of light bleaches rhodopsin into retinal and opsin
2) This keeps sodium channels closed so sodium does not enter the rod cells but leaves hyperpolarising the cell
3) Due to hyperpolarisation, glutamate is not released therefore an action potential can be passed on and generated in the bipolar cells

Question 4

Explain why visual acuity is better with our colour vision than with our grayscale vision

Answer 4

Our colour vision is controlled by cone cells. Cone cells all individually attach to their own bipolar and ganglion cells which all feed different visual/colour information to the optic nerve and the CNS. This ultimately produces a finer image. However, our multiple rod cells will connect to one bipolar cell all feeding the same information to the optic nerve so visual acuity worsens