Visual pathway

What is in the outer layer of the retina

photoreceptors, bipolar + horizontal dendrites

what is in the inner layer of the retina

bodies of horizontal, bipolar, and amacrines cells,

axons of bipolar, amacrines and dendrites of ganglions.

function of rods and cones in retina

generate graded potentials in response to light called photopigements.

rods - black and white vision

cones - colour vision

function of bipolar cells in retina

first neurone in the pathway to the brain, connected to photoreceptors.

what is the role of ganglion cells in the retina

A ganglion cell can receive one or more typically many bipolar inputs

• second neurone in the pathway

• axons make up optic nerve

• detect change in light themselves (effects circadian rhythm)

How do rods detect black and white

These cells generate graded potentials in response to light. The chemical responsible is called a photopigment.

In rods, this is known as rhodopsin.

It consists of two molecules: a large opsin protein long term, (non-disposable) and a small organic molecule called retinal, undergoes metabolic processing. Retinal derived from vitamin A

During light absorption, retinal undergoes synthesis again and must be recycled by the pigmented epithelium. Retinol → Retinal → Retinoic acid

What is the purpose of different opsin types (S.M,L)

short medium and long opsins code for different wavelengths of light that animals can see.

How is light converted to chemical then to electrical impulse?

light hits photoreceptor, inhibiting cGMP, stopping release of glutamate.