Vision Physiology

Question 1

What is the NT for light signal transduction?

Answer 1

Glutamate

Question 2

Describe high convergence

Answer 2

A larger number of photoreceptors share a ganglion. Good for amplifying signal in dark but not good for acuity
e.g. rods

Question 3

What is rhodopsin?

Answer 3

Retinal + opsin

Light sensitive vitamin A derivative + protein

Question 4

How does glutamate transduce a signal?

Answer 4

Glutamate is released during depolarisation
Light causes hyperpolarisation
In darkness there is lots of glutamate, in light there is less glutamate produced

Question 5

Describe pathway from light hitting receptor to hyper-polarisation

Answer 5

Light turns 11-cis-retinal to all-trans-retinal
Trans retinal activates GProtein Transducin
Transducin activates PDE which breaks up cGMP
cGMP are holding Na channels open and allowing it in
Less Na means hyperpolarisation

Question 6

Describe low convergence

Answer 6

Only a small amount of photoreceptors share a ganglion

e.g. cones

Question 7

What affect does light have on Retinal?

Answer 7

Turns 11-cis-retinal to all-trans-retinal

cis to trans