Retina And Vision

Question 1

Light reaches the photoreceptors and then its path to the ganglion cells of CNII =

Answer 1

Bipolar cells (also horizontal cells between adjacents)
Ganglion(also amacrine cells between adjacents)

Question 2

Retinal layer from superficial to deep

Answer 2

Ganglion cells
Bipolar cells
Photoreceptors

Question 3

Top to bottom components of photoreceptors

Answer 3

Synaptic terminals
Inner segment with cell body
Outer segment with membranous discs containing photopigment

Question 4

Depolarised resting potential of photoreceptors = ___

This is more/less positive than other neurons?

Answer 4

-20mV

More

Question 5

Channel important in the dark current

Answer 5

cGMP gated Na+ channel

Question 6

With light exposure photoreceptors ___polarise due to the ____

Answer 6

Hyper

Dark current

Question 7

Dark current channel is open and closed when?

Answer 7

Open - dark

Closed - light

Question 8

In the light the cGMP gated Na channels ____ and so Vm goes towards ____
Location of these channels =

Answer 8

Close
Ek (hyperpolarise)
Outer segment of photoreceptors

Question 9

Rhodopsin = ___+___

Answer 9

Retinal (vit A derivative)

Opsin (GPCR)

Question 10

Light converts ___>___ (activated form) in rods which activates ____ to activate ___ which hydrolysed cGMP to decrease its concn thus closing the ____

Answer 10

11-cis retinal
All trans retinal
Transducin(G protein)
cGMP PDE
cGMP gated Na channel

Question 11

___ converts all trans retinal to 11-cis retinal

Answer 11

Isomerase

Question 12

Neurotransmitter released by photoreceptors -

Increased release in ____

Answer 12

Glutamate

Dark

Question 13

Ability to distinguish two nearby points =

Answer 13

Visual acuity

Question 14

Visual acuity is determined largely by __+___

Answer 14

Photoreceptor spacing (more closer = better)
Refractive power

Question 15

Rods see in ____

____ spacing and ___ convergence => decreased ___ but increased ____

Answer 15

Dim light
Spacing
Convergence
Acuity
Sensitivity

Question 16

Cones see in ____

At fovea - ___ spacing and ___ convergence => increased __ and decreased ____

Answer 16

Normal light
Spacing
Convergence
Acuity
Sensitivity

Question 17

How many types of cones are there? What types are there?

Answer 17

3 - due to different opsins
Blue - short wavelength
Green - medium
Red - long

Question 18

Features of rods (5)

Answer 18

Achromatic
Peripheral retina
High convergence and light sensitivity
Low acuity

Question 19

Cones features

Answer 19

Chromatic
Foveal
Low convergence and light sensitivity
High acuity

Question 20

Right visual field > ___ cortex

Upper visual field > ___ cortex

Answer 20

Left

Lower

Question 21

Hebbs postulation for loss of binocularity:
Correlated activity between presynaptic and post synaptic cells strengthens ___
In monocular deprivation this results in ___

Answer 21

Arborisations

Less branches in LGN in deprived eye - rapid change