physiology of visual system

Question 1

primary visual pathway

Answer 1

light travels and hits retina - cones and rods
this goes to the thalamus in the lateral geniculate nucleus
this then travels to primary visual cortex (v1)

Question 2

difference between rods and cones

Answer 2

Rods are responsible for vision at low light levels (scotopic vision). They do not mediate color vision, and have a low spatial acuity.

Cones are active at higher light levels (photopic vision), are capable of color vision and are responsible for high spatial acuity. The central fovea is populated exclusively by cones.

Question 3

retina has different cells from anterior layer to postererior layer what Is the order of cells

Answer 3

bipolar cells - release glutamate depending on light

ganglion cells - final layer o freitna - send signals to bran

modulation cells - horizontal and amacrine cells

Question 4

receptive fields

Answer 4

area of retina where light stimulation induces a change in the membrane potential of the cells

bipolar and ganglion cells have receptive fields with an antagonistic centre-surround organisation

Question 5

hit head and affect temporal radiation and temporal bone then affect

Answer 5

upper quadrant visual field

Question 6

Lesions of the LGN most frequently result from infarction of the

Answer 6

anterior or lateral choroidal arteries.

Question 7

ocular dominant columns

Answer 7

visual information is kept segregated by eye and cell type forming ocular dominant columns in layer 4

Question 8

binocularity

Answer 8

layer 4 cells from ocular columns send converging projections to upper layers

appears in upper layer soft the cortex for the first time

responses are still dominated by one eye

underpins ability to see in 3d

Question 9

receptive fields in primary visual cortex

Answer 9

layer 4 - similar to LGN and retina

layer 3 - receives convergent inputs from layer 4 cells - elongated receptive fields

most receptive fields have centre- surround antagonism ( on/off areas spatially segregated)

Question 10

orientation and direction selectivity

Answer 10

selective response to the orientation and direction of movement

orientation selective neurones - analysis of object shape

direction selective neurones - analysis of object motion

Question 11

lesions affecting V1 produce what

Answer 11

contralateral scotomas - areas of the visual field with degenerated visual acuity that are surrounded by areas of normal vision

Question 12

extra striate visual cortex

Answer 12

dorsal pathwya
analysis of motion
visual control of action

ventral pathway
object recognition, colour perception

Question 13

upper part of retina , retina fibres contain visual information from lower visual field and vv

Answer 13

these travel straight to visual cortex superior to calcarien sulcus

lower part - round inferior to the calcimine sulcus

meyers lope

Question 14

upper part of retina , retina fibres contain visual information from lower visual field and vv

Answer 14

these travel straight to visual cortex superior to calcarien sulcus

lower part - round inferior to the calcimine sulcus

meyers lope - temporal visual field

Question 15

upper part of retina , retina fibres contain visual information from lower visual field and vv

Answer 15

these travel straight to visual cortex superior to calcarien sulcus

lower part - round inferior to the calcimine sulcus

meyers lope - temporal visual field- round temporal bone