physiology of vision

Question 1

What are some common focusing problems

Answer 1

Hypermetropia (long-sightedness): eyeball too short or lens system is to weak so light rays are focused behind the retina

myopia (short-sightedness) : eyeball too long or lens system is too strong so light rays are focused in front of the retina

Question 2

Outline the structure of the retina

Answer 2

120 million rods (dim light), 5 million cones (colour and bright light)

processing layers:
3 direct layers ( receptors, bipolars and ganglion cells)
2 transverse layers ( horizontal cells and amacrine cells)

Question 3

What is Rhodopsin

Answer 3

It is a photosensitive pigment in the rods, when hit by photon there is a chemical change which sets of a series of biochemical events that close c GMP- gated nonselective cation channels that are open in the dark, leading to hyperpolarisation of the photoreceptor and the reduction in NTM glutamate release

Question 4

How is colour blindness caused and what does it do

Answer 4

results in loss or mod of one or more of the 3 cones visual pigments,

males have only one x chromosome.