Physiology Of Vision

Question 1

What are the 3 primary accessory structures of the eye?

Answer 1

Palpebrae (eyelids)

Superficial epithelium of the eye

The lacrimal apparatus
- prime producer of tears

Question 2

What is the pathway of tears?

Answer 2

Start from production from the lacrimal apparatus

Then move:

1) lacrimal lake
2) lacrimal puncta
3) lacrimal canaliculi
4) lacrimal sac
5) nasolacrimal duct
6) inferior meatus of the nose

Question 3

The photoreceptor mechanism

Answer 3

1) retina absorbs light and changes shape and activates visual pigment

2) visual pigment activates transducin
- this is a G-protein

3) transducin activates phosphodiesterase
4) phosphodiesterase converts cGMP -> GMP
5) GMP increases cause hyperpolarization in photoreceptors

Question 4

What vitamin is required to induce pigment synthesis?

Answer 4

Vitamin A

Question 5

Cone physiology

Answer 5

Inner segment
- contains the cell nucleus and mitochondria

Outer segment
- houses discs of rhodopsin (site of actual light interpretation

Question 6

Color blindness

Answer 6

Sex-linked recessive disorder where one or more cone mechanisms are lost

Protanopia = absent of long wavelength cones (red)

Deuteranopia = absent of medium wavelength cones (green)

Tritanopia = absent of short wavelength cones (blue)