Lecture 3.1-3.2: Vision

Question 1

region of the retina that supports high visual acuity

Answer 1

macula - especially fovea

Question 2

Absorption of light by the photoreceptor reduces the concentration of

Answer 2

cGMP, leading to a closure of cGMP-gated Na+ and Ca2+ channels and subsequent hyperpolarisation of the cell

Question 3

Mechanism of closure of cGMP-gated channels

Answer 3

Retinal coupled to an opsin absorbs a photon of light, and changes its configuration from 11-cis to all-trans. This triggers a change in the opsin component which leads to the activation of transducin. This activates a phosphodiesterase which hydrolyses cGMP.

Question 4

a single light-activated rhodopsin molecule can activate

Answer 4

800 transducin molecules

Question 5

optic disk

Answer 5

where retinal ganglion axons gather to exit the retina. Optic disk is devoid of photoreceptors

Question 6

M (parasol) ganglion cells

Answer 6

motion detection
magnocellular (large)
large receptive fields

Question 7

P (midget) ganglion cells)

Answer 7

parvocellular (small)

visual acuity and colour

Question 8

Visual pathway

Answer 8

Retina -> optic nerve -> lateral geniculate nucleus in the thalamus -> optic radiations -> visual cortex

Question 9

LGN neurons project to the

Answer 9

primary visual cortex (BA17)

Question 10

M and P ganglion cells input to which layer in the cortex

Answer 10

4C

Question 11

Middle temporal lobe of the dorsal stream is required for

Answer 11

processing object motion

Question 12

Ventral stream is important for

Answer 12

object recognition and perception of shape and colour