Physiology of Vision

Question 1

Cellular Structure of the Retina?

Answer 1

The cells in the retina are organized inside-out: the first cells to receive stimulation are the innermost photoreceptors, and the cells that exit the eye to carry information to the brain are the outermost cells
Direct (vertical) pathway for signal transmission:

Ganglion cells
^
Bipolar cells
^
Photoreceptors (first)

Lateral connections influence signal processing :
Horizontal cells, Receive input from photoreceptors and project to other photoreceptors and bipolar cells
Amacrine cells, Receive input from bipolar cells and project to ganglion cells, bipolar cells, and other amacrine cells

Question 2

Visual acuity

Answer 2

• ability to distinguish two nearby points, determined largely by photoreceptor spacing and refractive power
• Facilitated by the distribution of rods and cones

Question 3

Photoreceptors

Answer 3

• Converts electromagnetic radiation to neural signals (transduction)
• Two types: rods and cones

Photoreceptor structure

• Outer segment
• Inner segment
• Cell body
• Synaptic terminal

Question 4

Rods?

Answer 4

More convergence in rod system → increasing sensitivity while decreasing acuity
seeing in dim light/dark

• Achromatic-without colour
• Peripheral retina
• High convergence (large spacing)
• High light sensitivity
• Low visual acuity

Question 5

Cons?

Answer 5

seeing in normal daylight

• Chromatic-colour
• Central retina (fovea)
• Low convergence
• Low light sensitivity
• High visual acuity

Question 6

Distribution of Rods and Cones?

Answer 6