Vision

Question 1

Where is the blind spot?

Answer 1

Optic disc in retina, where blood vessels enter and leave, and where the optic axons exit the eye

Question 2

Why is the blind spot ‘blind’?

Answer 2

There are no photoreceptors present

Question 3

What is the visual field?

Answer 3

The limitations of what can be seen when the eye fixates on an object

Question 4

Use of opthalmoscope

Answer 4

Makes the interior of the eye visible - gives a view of retina, its blood vessels and optic disc (due to light reflected by subjects eye)

Question 5

Most common colour vision abnormality

Answer 5

Red-green colour-blindness

Question 6

Which cells in the retina produce action potentials?

Answer 6

Ganglion cells

Question 7

Which cells in the retina produce graded responses?

Answer 7

Bipolar cells - transmit signals from photoreceptors or horizontal cells to ganglion cells either directly or indirectly

Question 8

Which neurotransmitter is released by photoreceptors?

Answer 8

Glutamate

Question 9

When are photoreceptors depolarised?

Answer 9

In dark light - therefore a high amount of glutamate is released to bipolar cells in the dark

Question 10

How do rod and cone cells signal the absorption of photons?

Answer 10

Via a decrease in release of glutamate to bipolar cells

Question 11

Do M-type or P-type ganglion cells respond to different colour stimuli?

Answer 11

P-type
Information from either a single cone or a group of the same type of cones
Wavelength specific

Question 12

Do M-type or P-type ganglion cells respond best to moving stimuli?

Answer 12

M-type

Fast, transient responses

Question 13

Type of receptor in OFF-centre bipolar cells

Answer 13

AMPA/Kainate (ionotropic)

Question 14

Type of receptor in ON-centre bipolar cells

Answer 14

mGluR6 and TRPM1 (metabotropic)

Question 15

What does an increased NT release cause OFF-centre bipolar cell receptors to do?

Answer 15

Depolarise the cell

Glutamate binds to receptor and opens channel so cations flow through and depolarise the cell

Question 16

What does an increased NT release cause ON-centre bipolar cell receptors to do?

Answer 16

Hyperpolarise the cell
Glutamate binds to mGluR6 which activates Galphao
This inhibits TRPM1 so no entrance of cation therefore hyperpolarisation

Question 17

Which layer(s) of the LGN would information about a black and white, fast-moving stimulus project to?

Answer 17

Magnocellular layer - M-type
From the contralateral side: layer 1
From the ipsilateral side: layer 2

Question 18

Which layer(s) of the LGN would information about a coloured, stationary stimulus project to?

Answer 18

Parvocellular layer - P type
From the contralateral side: layers 4 and 6
From the ipsilateral side: layers 3 and 5