Topic 8: Grey Matter

Question 1

What happens in rod cells in the dark?

Answer 1

The cation channels are open
sodium ions diffuse down concentration gradient and are actively pumped out
and this causes the membrane to depolarise slightly (-40 mv)
Releases neurotransmitters which diffuse across synapse
Bind to receptors on the bipolar cell and this prevents action potential from being fired since it prevents depolarisation

Question 2

What happens to rod cells in the light

Answer 2

Rhodopsin is broken down into retinal and opsin
Opsin causes a cascade of reactions which lead to the cation channels to close
No sodium ions can enter and the sodium ions already in the rod cell are actively pumped out