Vision

Question 1

How much light does the cornea bend?

Answer 1

2/3

Question 2

How much light does the lens bend?

Answer 2

1/3

Question 3

Hypermetropia?

Answer 3

Long sightedness _ eyeball too short or lens too weak

Question 4

Myopia?

Answer 4

Short sightedness - eyeball too long or lens too strong

Question 5

Refractive power is measured in?

Answer 5

Diopters {D}

Question 6

Refractive power and focal length?

Answer 6

2d has focal length of 0.5m

It is reciprocal

Question 7

What kind of corrective lens is needed?

Answer 7

Hyperopic-converging myopic- diverging

Question 8

How many receptors?

Answer 8

120 million rods (dim)

5 million cones (bright)

Question 9

Processing layers of retina?

Answer 9

3 direct-receptors, bipolar cells, ganglion cells

2 transverse layers- amacrine and horizontal cells.

Question 10

How does rhodopsin work?

Answer 10

Photosensitive pigment in rods

When photon hits the retinal. It causes 11 cis to all trans flip causing closure of cGMP gated cation channels which are open in the dark leading to hyperpolarisation of the photoreceptors and a reduction in the release of glutamate

Question 11

Ganglion cell response?

Answer 11

Local contrast on and off lateral inhibition.

Question 12

What kind of potential in retinal cells?

Answer 12

Ganglion - action potential receptors and bipolar - graded potential

Question 13

Colour wavelength?

Answer 13

Red: 560
Green: 530
Blue: 420
Rods: 500

Question 14

Genes for green and red are where?

Answer 14

X chromosome

So males colour blindness is 7%
And 0.5% in females

Question 15

Where is blue colour gene?

Answer 15

Chromosome 7

Question 16

Central achromatopsia?

Answer 16

Damage to cortical colour processing area V4

Question 17

What is simple cell response in V1?

Answer 17

From rows of ganglion cells or LGN, on and off centre fields

Question 18

Brodmann 17 area is divided into?

Answer 18

Ocular dominance columns, orientational columns and colour blobs.

Hypercolumn contains all 3

Question 19

Homonymous hemianopia?

Answer 19

After optic chiasam lesion so you lose same side of both eye, both lefts

Question 20

Bitemporal hemianopia?

Answer 20

Can’t see lateral sides of eyes, this is due to compression or damage to optic chiasm

Question 21

Scotoma?

Answer 21

Could be defect in area of visual field, retinal damage pressure of tumours restricting th optic never, chiasm, optic tract or optic radiation

Question 22

Ventral stream is responsible for?

Answer 22

To temporal cortex, object identity and conscious perception

Question 23

Dorsal stream is responsible for?

Answer 23

To parietal cortex,location, motion and action.

Question 24

Visual agnosia?

Answer 24

Inability to recognise visually presented objects.

Cannot identify orientation of card in slot?

Question 25

Optic ataxia?

Answer 25

Can describe but not act. So knows orientation but cannot place card in slot

Question 26

Prosopagnosia?

Answer 26

Inability to recognise faces, in fusiform gyrus in temporal lobe.

Question 27

Blindsight?

Answer 27

Destruction in v1, leading to blindness in that area, individuals can still perform discrimination tasks.. happens because projections from LGN and superior colliculus reach cortical, areas bypassing V1

Question 28

What does vestibulo ocular reflex do?

Answer 28

Stabilises gaze by countering movement of head

Question 29

Optokinetic reflex?

Answer 29

Stabilises image of moving object on retina

Question 30

What happens in pupillary reflex?

Answer 30

Illumination Will cause contraction of both eye due to pretectal nuclei and edinger- westphal nuclei.

Question 31

How many retinal ganglion cells per eye?

Answer 31

1 million per eye 125:1 convergence into optic nerve

Question 32

Optic tracts relay into?

Answer 32

Lateral geniculate nuclei of thalamus

Question 33

A part of each tract goes to the ?

Answer 33

Superior colliculus in the mid brain

Question 34

After the lateral geniculate nuclei the output goes exclusively to?

Answer 34

Striate Cortex of occipital lobe V1

Question 35

Colour information is passed onto regions such as?

Answer 35

V4

Question 36

What is consensual response?

Answer 36

If light shone in eye with optic nerve damage, then that eye wont contract but other will

Question 37

What happens if there’s a damage to one oculomotor nerve?

Answer 37

No pupil contraction in that eye, but stimulation of either eye will cause contraction in the pupil of second eye