VISION

Question 1

What pigment do rods use in the photoreceptor transduction cascade?

Answer 1

RHODopsin

Question 2

What pigment do cones use in the photoreceptor transduction cascade?

Answer 2

Photopsin

Question 3

Which vitamin is involved in rhodopsin synthesis?

Answer 3

vitamin A

Question 4

what are the two molecules that form rhodopsin?

Answer 4

retinal (a.k.a retinaldehyde)

opsin

Question 5

what is the difference between photopsin and rhodopsin?

Answer 5

There are 3 types of photopsin; I, II and III, all absorb different wavelengths of light

Question 6

what is the light absorbing component of photopigments?

Answer 6

retinal

Question 7

once retinal has absorbed light, which conformation will if be found in?

Answer 7

all TRANS retinal

Question 8

what is the function of the opsin portion of the photopigment?

Answer 8

determines what wavelength of light is absorbed by retinal

binding of retinal

Question 9

what wavelength of light is absorbed by rods?

Answer 9

498nm

Question 10

what wavelength of light is abosrbed by red cone opsins?

Answer 10

564nm

Question 11

what wavelength of light is absorbed by green cone opsins?

Answer 11

533nm

Question 12

what wavelength of light is abosrbed by blue cone opsins

Answer 12

433nm

Question 13

what in the structure of various opsin molecules determines which part of the light spectrum they will absorb?

Answer 13

amino acids that surround the retinal binding site

Question 14

How do photoreceptors response to light exposure?

Answer 14

Graded hyperpolarisation e.g. if there is more light expsoure, there will be more hyperpolarisation

Question 15

in the dark, how much glutamate do photoreceptors release into synapse with bipolar cells?

Answer 15

GLUTAMATE RELEASED IN ABUNDANCE

Glu is inhibitory at this stage

Question 16

in the light, how much glutamate do photoreceptors release into the synapse with bipolar cells?

Answer 16

GLUTAMATE NOT RELEASED

Glu is inhibitory, therefore net excitation on post-synaptic bipolar cell

Question 17

which photoreceptors are more sensitive to light?

Answer 17

Rods

Question 18

what is the function of the horizontal cells?

Answer 18

provide antagonistic responses to photoreceptor activation via GABA @ outer plexiform layer

Question 19

what is the function of amacrine cells?

Answer 19

Amacrine cells are inhibitory neurons, and they project their dendritic arbors onto the inner plexiform layer (IPL), they interact with retinal ganglion cells and/or bipolar cells

Question 20

what is a ‘receptive field’ of a ganglion cell?

Answer 20

The area of the retina in which light absorption excites a single retinal ganglion cell

Question 21

what is the ‘on-centre’ pathway?

Answer 21

pathway in which the synapse between a photoreceptor and bipolar cell is sign INVERTING i.e. glutamate in inhibitory to bipolar cell and pathway is excited when its light

Question 22

what type of glutamate receptors are found in the on-centre pathway?

Answer 22

sign inverting metabotrophic glutamate receptors

Question 23

what is the ‘off centre’ pathway?

Answer 23

pathway in which the synapse in the outer plexiform layer is sign CONSERVING i.e. glutmate is excitatory. Glu released in abundance when its dark, which excites off centre ganglion cells

Question 24

what type of glutamate receptors are found in the off-centre pathway?

Answer 24

sign conserving ionotrophic glutamate receptors

Question 25

what are the two continuums of colour axis differentiation?

Answer 25

Red - Green Blue - Yellow Cones of different colours side by side in receptive fields produce information on colour based on how inhibited/excited the central bipolar cell is

Question 26

axons from which half of the RETINAL field decussate at the optic chiasm?

Answer 26

NASAL

Question 27

axons from which half of the VISUAL field decussate at the optic chiasm?

Answer 27

TEMPORAL

Question 28

where do fibres of the optic tract terminate?

Answer 28

lateral geniculate nucleus of thalamus

Question 29

some fibres leave the optic tract and travel to the pre tectal nucleus. What are these fibres function?

Answer 29

afferent limb of pupillary reflex

Question 30

what is the structure/function of baums loop?

Answer 30

division of the optic radiation transmits information relating to the SUPERIOR retinal field Travels via the parietal lobe

Question 31

what is the structure/function of meyers loop?

Answer 31

division of the optic radiation transmits information relating to the INFERIOR retinal field Travels via the temporal lobe

Question 32

a lesion that blocks the optic nerve of that eye, resulting in blindness in that eye....

Answer 32

Anopia

Question 33

a lesion at the optic chiasm, causing temporal visual field defects in both eyes...

Answer 33

bitemporal hemianopia

Question 34

what is the a common cause of bitemporal hemianopia?

Answer 34

pituitary adenoma

Question 35

a lesion in the right/left optic tract, causing both nasal and temporal visual defects...

Answer 35

homonomous hemianopia

Question 36

a lesion affecting meyers loop...

Answer 36

upper homonomous hemiquadrantanopia

Question 37

a lesion effecting baums loop...

Answer 37

lower homonomous quadrantantopia

Question 38

a lesion in the primary visual cortex...

Answer 38

homonomous hemianopia with central sparring

Question 39

when light is in the centre of an 'on centre' cell, it is...

Answer 39

excited

Question 40

when light is in the centre of an 'off-centre' cells, it is...

Answer 40

inhibited | via lateral inhibition of horizontal cells

Question 41

when light is in the annulus/periphery of an on centre cell, it is...

Answer 41

inhibited

Question 42

when light is in the annulus/periphery of an off centre cell, it is...

Answer 42

excited

Question 43

what is myopia? how is it corrected?

Answer 43

shortsightedness- distant objects are blurred, near objects are seen clearly corrected with concave lens

Question 44

what is hypermetropia? how is it corrected?

Answer 44

longsightedness- both far and near objects are blurred corrected with a convex lens

Question 45

what is presbyopia? how is it corrected?

Answer 45

age-related longsightedness due to lens fibre deposition with age convex lens correction

Question 46

what is astigmatism? how is it corrected?

Answer 46

non-spherical curvature of the lens, meaning refraction isn't equal throughout corrected using a spherical lens

Question 47

how is visual acuity tested?

Answer 47

snellen chart

Question 48

a patient records a snellen chart fraction of 6/40. what does this mean?

Answer 48

6 - how far away the patient is (m) | 40 - how far away the average person would be to read the symbols

Question 49

what is the test for colour blindness?

Answer 49

ischihara test plates

Question 50

how are visual fields tested?

Answer 50

confrontation testing | goldman perimeter testing

Question 51

heterotropia, crossed eyes and squint are laymans terms for which visual condition?

Answer 51

Strabismus

Question 52

what is the medical name for 'lazy eye'?

Answer 52

amblyopia