the eye and the retina

Question 1

Functional anatomy of the retinal circuitry that gives rise to ganglion cell receptive fields

Answer 1

-retinal pigment epithelium
-photoreceptor layer
-interneurone layer(bipolar)
-ganglion cell

Question 2

how do off-center ganglion cells respond to a decrease in illumination (including photoreceptor and bipolar)

Answer 2

A reduction in illumination results in rod cells depolarizing, while in turn, bipolar cells mimic the response of photoreceptors and also depolarize, which leads to the firing of AP by ganglion cells, sending these impulses to the brain.

Question 3

how do off-center ganglion cells respond to an increase in illumination (including photoreceptor and bipolar)

Answer 3

and increase in illumination results in hyperpolarization of photoreceptors (cones); bipolar cells also mimic this response, also hyperpolarizing, inhibiting firing of AP by ganglion cells.

Question 4

what type of cells allow us to see increase and decrease in illumination

Answer 4

off and on centre ganglion cells

Question 5

how do on-center ganglion cells respond to an increase in illumination (including photoreceptor and bipolar)

Answer 5

Photoreceptors hyperpolarize with an increase in illumination, resulting in the depolarization of bipolar cells and the firing of AP by ganglion cells, which send these impulses to the brain.

Question 6

why do on-centre bipolar cells depolarise when the connecting photoreceptor hyperpolarises in response to an increase in illumination?

Answer 6

Normally, glutamate will bind to the MGluR6 on the on bipolar cells closing the sodium channels but in this case, as there’s less glutamate release from the photoreceptor, less of it will bind to this receptor, hence the sodium channels will stay open, leading to depolarization.

Question 7

what type of receptors are found on bipolar on-centre and bipolar off-centre cells

Answer 7

metabotropic (MGluR6) - on-centre
ionotropic (iGluR) - off-centre

Question 8

what is the function of horizontal cells

Answer 8

they work by receiving inputs from photorecptors and bipolar cells and sending feedback to neighboring photoeceptors and bioplars cells. this enhances our visual contrast by sharpening the edges, making it easier to the border which is especially done via lateral inhbition (inhibiting neighboring photoreceptors and bipolar cells activity)

Question 9

describe magnocellular cells in terms of spatial and temporal resolution/frequency

Answer 9

low spatial and high temporal (not as effective in discrimination of fine detail but can respond to rapid changes in visual stimuli)

Question 10

describe parvocellular cells in terms of spatial and temporal resolution/frequency

Answer 10

high spatial and low temporal (very effective in discrimination of fine detail but can’t respond well to rapid changes in visual stimuli)