Human Visual System 1

Question 1

2 roles of the chamber of the eye??

Answer 1

-> exclude light, except that which enters thru the cornea & pupil
-> focus an image, of world onto retinal surface

Question 2

structure of the retina??

Answer 2

structure of the retina is complex, multilayered, contains cell bodies between layers of nerve fibres and dendrites

Question 3

why can’t you see your blood vessels??

Answer 3

Blood vessels are fixed in position with respect to retina, attached and move with it-> stabilised image

Question 4

how many types of photopigment do cones have??

Answer 4

3 types of photopigment (L,M,S)

Question 5

how many types of photopigment do rods have??

Answer 5

1 type of photopigment-> Rhodopsin

Question 6

Cones density wrt fovea??

Answer 6

good acuity -> colour vision, high density in central fovea enabling high acuity and rapid fall in density away from fovea

Question 7

Rods density wrt fovea??

Answer 7

good light sensitivity -> achromatic (no colour vision) absence of rod in fovea -> ‘night blind’, high density of rods in periphery

Question 8

ganglion cells??

Answer 8

-> final output neurons of the vertebrate retina

Question 9

The 2 major types of Ganglion cells in the retina:

Answer 9

Magnocellular (M) cells
Parvocellular (P) cells

Question 10

Magnocellular (M) cells:

Answer 10

receive inputs from many photoreceptors
respond faster and respond to transient/moving stimuli
poor spatial resolution since they combine inputs from many photoreceptors

Question 11

Parvocellular (P) cells:

Answer 11

receive inputs from fewer cones
have high spatial resolution
play a key role in colour vision