Retina

Question 1

the […] is an area of the retina that controls central vision. It’s loss causes blindness and its dysfunction is implicated in macular degeneration.

Answer 1

fovea

Question 2

in photopic light conditions, the best visual acuity is [….] focused on […] in the fovea.
whereas in scotopic light levels, best VA is [….] at […..].

Answer 2

6/6
cones

6/60
rods and rod pathways

Question 3

light passes through all the retinal layers prior to hitting the photoreceptors, name them in succession

Answer 3

inner plexiform layer
inner nuclear layer
outer plexiform layer
outer nuclear layer

Question 4

rods are specialized for [….] vision, or […] conditions.
approx how many are there?
which part of retina are they absent from?

Answer 4

night vision
scotopic conditions

100 million
absent from fovea

Question 5

cones are specialized for [….] vision, or […] conditions.
how many types?
approx how many are there total?
which part of retina are they densest?

Answer 5

day vision, photopic conditions, AND color vision
3 types
densest in the fovea

Question 6

describe the 3-part ‘through pathway’ of the retina?
photoreceptors —> ? —-> ?

modification of the through pathway occurs by […..] and […] cells

Answer 6

photoreceptors link to bipolar cells link to ganglion cells

amacrine cells and horizontal cells.

Question 7

in the through pathway, there are ten types of bipolar cells, 1 is a rod bipolar cell, the other 9 are [….] cells

Answer 7

cone bipolar cells.

Question 8

horizontal cells receive input from photoreceptors and then function to laterally inhibit photoreceptors via the NT, [….]. They respond to light by […].

Answer 8

GABA.

hyperpolarizing.

Question 9

amacrine cells are axonless cells that are important for […].
They release the NT’s:

These are responsible for modifying the way bipolar cells signal on to […..] cells.

Answer 9

lateral inhibition.
GABA and glycine.

ganglion

Question 10

the ganglion cell layer contains ganglion cell bodies and some displaced […..] cells.

the ganglion cells are the main output neurons of the retina, there are several types: [….]

These cells release the NT, [….], and are the only ones within this through pathway that are capable of [….]

Answer 10

amacrine.

on, off, P (color), and M (motion)

glutamate
firing action potentials.

Question 11

ganglion cells respond to light by increase or decreasing […..]

Answer 11

their action potential firing rate.

Question 12

the […..] of a ganglion cell or bipolar cell is the area of retina that when stimulated with light changes the cells membrane potential.

Answer 12

receptive field

Question 13

the concentric-sorround receptive field of the ganglion cell means that

Answer 13

depending on where the light hits the ganglion receptive field a very different message is communicated onwards

Question 14

photoreceptors contain […] allow them to respond to light.

rods contain the photopigment, [….].
cones contain the photopigments, [….]

All -opsins bind to [….].

Answer 14

photopigments.

rhodopsin
cone-opsins (few types)

Vitamin A (all-trans retinal)

Question 15

in response to light, photoreceptors become […..] and use […] as their NT.

Since only [….] cells depolarize in the ‘through pathway’, instead photoreceptors respond to light with [……] in membrane potential.

Answer 15

hyperpolarized.
glutamate.

ganglion.
graded changes

Question 16

in the dark, photoreceptors have […..] molecular that creates a sodium channel —> allowing continuous influx of sodium ions –> causes […]

Answer 16

cGMP

depolarization of the cell.

Question 17

in light conditions, light causes cGMP within the photoreceptor to break down into […..]. —> flow of Na ions into the cell ceases —> cell becomes [….]

Answer 17

GMP

hyperpolarized.

Question 18

OFF bipolar cells become […] in response to light, whereas ON bipolar cells become [….] in response to light.

This is because ON bipolar cells have […..] glutamate receptors and OFF bipolar cells have [….] glutamate receptors.

Answer 18

hyperpolarized
depolarized

ionotropic. (protein subunits–>form an ion channel)
metabotropic (second messenger cascade)

Question 19

what interaction is there between photoreceptors and on/off bipolar cells and on/off ganglion cells.

Answer 19

photoreceptors communicate with both ON and OFF bipolar cells.in

ON bipolar cells only communication with ON ganglion cells.

OFF bipolar cells only communicate with OFF ganglion cells.

Question 20

in the centre-sorround receptive field organization, the central response is determined by the […] and the sorround response is determined by […].

Answer 20

through pathway
horizontal cells (acting as interneurons)

Question 21

Horizontal cells receive input from many photoreceptors and provide output to [….].

the ‘sorround response’ results from the action of Horizontal cells on the [….] of photoreceptors.

Answer 21

other photoreceptors.

“central” group”