Physiology Of Vision

Question 1

Layers of functional structure of eye ball

1. Sclera and cornea
2. Choroid, ciliary body and iris
3. Retina

Answer 1

1. Fibrous layer
2. Vascular and pigmented
3. Photoreceptor

Question 2

Photoreceptor cells

Answer 2

Cones

Rods

Question 3

Describe retina visual pathway

Answer 3

Photoreceptor cells > synaps to bipolar cells > synapse to ganglion cells

Question 4

Blood supply of retina

Answer 4

1. Central retinal artery

2. Choroid capillary plexus

Question 5

Describe optic disc

Answer 5

Point where optic nerve leaves the eyes and retinal vessel enter

Question 6

Describe

1. Macula lutea
2. Fovea centralis

Answer 6

1. Yellow pigmentation surround the fovea

2. Fovea that contains cones only

Question 7

Visual pathway 1

Answer 7

Light rays converted to AP > conducted to optic nerve > medial optic nerve decussate at the optic chiasm > enter optic tract > lat geniculate body of thalamus > primary visual cortex area 17 (through geniculocalcarine tract)

Question 8

Other visual pathway and its concern

Answer 8

1. Optic fibers end in pretectal nuclei and sup colliculi - concerned for pupillary reflex
2. Axons pass directly from optic chiasm to suprachiasmatic nuclei in hypothalamus - concerned for circadian rhythm

Question 9

Lesion of primary visual cortex

Answer 9

Visual agnosia - cannot interpret symbols and letters

NOTES: Visual motor cortex deal with object and face recognition

Question 10

Visual pathways lesion location

1. Monocular blindness
2. Heteronymous bitemporal hemianopia
3. Homonymous hemianopia
4. Homonymous hemianopia with macula sparing

Answer 10

1. One side of optic nerve
2. Optic chiasm
3. One optic tract
4. One geniculocalcarine tract

Question 11

Rhodopsin is a light sensitive photopigment contain in membranous disc of photoreceptor cells. What is its 2 components?

Answer 11

Opsin

Retinene (derivative of Vit A)

Question 12

Mechanism on photoreceptors in dark

Answer 12

Na gate open > depolarize > release of inhibitory neurotransmitter from rods > no activation of bipolar and ganglion cells

Question 13

Mechanism of photoreceptors in light

Answer 13

Na gate close > hyperpolarization of cones > no inhibitory neurotransmitter release > bipolar cells release excitatory neurotransmitter to ganglion cells > generate AP of optic nerve

Question 14

Photoreceptors for colour vision

Answer 14

Cones cells

Question 15

Describe 3 types of cones

1. S cones
2. M cones
3. L cones

Answer 15

1. Most sensitive to short wavelength - perception of blue
2. Most sensitive to medium wavelength - perception of green
3. Most sensitive to long wavelength - perception of red