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BS0012 > The Eye > Flashcards

The Eye Flashcards

1
Q

Sclera

A

White of the eye tough white skin that protects and covers all of the eye except cornea supports eyeball provides attachments for muscles

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2
Q

Cornea

A

Is the clear portion of the sclera allows light into the eye acts as fixed lens two thirds of light refraction takes place in cornea

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3
Q

Pupil

A

Size determines amount of light entering eye bright light pupil constricts dim light pupil dilates

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4
Q

Iris

A

Parasympathetic stimulation causes circular muscles to contract,sympathetic stimulation causes radical muscles to contract 1. Coloured part of eye
2. Circular muscle

3.controls opening of pupil

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5
Q

Lens

A
  1. Made of transparent fibres in clear membrane
  2. Allows precise focusing of light onto retina
    3.suspended by ligament
    4.finefocussing mechanism
    5.non uniform index of refraction
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6
Q

Aqueous humour and vitreous humour

A
  1. Transparent gel like liquid filling the eye
    2.provides nutrient too cornea and eye lens
    3.helps maintain eye ball shape with its pressure
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7
Q

Retina

A

1.internal membrane
2.contains light receptive cells cones and rods
3. Converts light to electric signals
4.signals leave eye via optic nerve

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8
Q

Optic nerve

A

1.transmits electrical impulses from retina to brain
Blind spot

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9
Q

Focussing light onto retina

A

Light is focussed at cornea entering lens exiting lens lens curvature and shape allow for fine focussing of an image

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10
Q

Focussing for distance and near viewing

A

The lens has a small depth of field
Cannot see something close and far with both objects in focus at the same time

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11
Q

Accommodation distance and near

A

Distance light rays almost parallel do not need as much refraction ciliary muscles relaxed fibres taut flat lens
Near light rays diverge need more refraction ciliary. Muscles contract fibres slack rounded lens greater strength for near vision

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12
Q

Presbyopia

A

Lens harden with age
Cannot accommodate for near
Bifocal lenses

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13
Q

Retina

A

Receives light focussed by lens convert light via network of nerve cells

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14
Q

Choroid

A

Vascular layer providing oxygen and nutrients to outer retina especially fovea
Absorbs any light not absorbed by photoreceptors

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15
Q

Retinal pigment epithelium

A

Pigment layer for light absorption. Sand reducing oxidative stress tight junctions and blood brain retina barrier supports photoreceptors

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16
Q

Cones

A

Concentrated in fovea high acuity day vision and colour vision

17
Q

Rods

A

Dark vision Not present in central retina

18
Q

Horizontal cells

A

Interneurons connecting photoreceptors laterally help integrate and regulate from multiple photoreceptors cells

19
Q

Bipolar cells

A

Connect photoreceptors to retinal gangalion cells
Facilitate sensory processing through horizontal amacrine cells

20
Q

Amacrine cells

A

Interneurons connecting bipolar laterally
Inhibitory
Interact with retinal gangalion cells

21
Q

Retinal ganglion cells

A

Out
It cells from retina relay info from retina to brain via optic nerve
4 types in humans parvocellular magnocellular Kongo cellular photosentive ganglion cells

22
Q

Rod cells

A

120 million throughout retina
Absent from fovea
Rod shaped
Sensitive to dim light not sensitive to colour
Many rods feed into one ganglion cell poorly resolved images
Light sensitive pigments rhodopsin low visual acuity but good indark

23
Q

cones

A

6-7 million condensed at fovea cone shaped require bright light 3 types for colour vision 1 cone feeds into 1 ganglion cell at fovea well resolved images light sensitive pigments iodopsin high visual acuity and colour vision

24
Q

Phototransduction

A

Recess through which light is converted into electrical signals occurs in the retina through photoreceptors to encodes a light stimulus as chemical output deception to encodes a light carried out on membrane disks contain 1000s of molecules or rhodopsin

25
Q

Phototransduction

A

Rhodopsin contains ops in protein and retinal
Dark=cis form
Absorbs light=trans form
Changed shape of ops in protein bleaching
Reverse action trans to cis requires enzyme reaction and is very. Slow

26
Q

Path of Phototransduction

A

Light changes rhodopsin structure then alters permeability to na+ in photoreceptors then sensory neurone in optic nerve then to brain

27
Q

Lateral geniculate nucleus

A

Structure in thalamus part of midbrain receives input from retinal ganglion cells input and output connections to visual cortex one in each to sphere one in each hemisphere leave LGN and goes to visual cortex

28
Q

Primary visual cortex

A

Located in occipital lobe input from LGN via optic radiation send information to 2 pathways
1) ventral stream from recognition a object presentation
3) Dorsal stream motion object location eye and arm control

29
Q

Depth perception.

A

Retinal disparity allows judgment of distance
The closer an object the great and disparity
Requires binocular vision

30
Q

Visual Disease sclera

A

Scleritis inflammation of sclera usually associated with u derlying disease can progress to other parts of the eye immediate treatment to reduce long term vision loss

31
Q

Visual disease cornea

A

Open sore of the cornea many causes infection physical chemical trauma corneal drying over contact lenses very serious may result in blindness

32
Q

Disease in pupil and iris

A

Colombo a hole in iris underdeveloped tissue during pregnancy can be syndromes or caused by foetal alcohol syndrome variable impact on vision treatment coloured contact lens

33
Q

Visual disease lens

A

Cataracts age related congenital or trauma clouding of lens decrease vision surgery removal of old lens via suction and insertion of plastic lens

34
Q

Disease in retina macular degeneration

A

Age related degeneration affects retina build up of was5e occurs in 50 to 60 year olds. Progressive without treatment injections mild vision lost

35
Q

Retinal detachment

A

Tear allows fluid under retina risk
Risk trauma family history
Surgery

36
Q

Strabismus

A

Misalignment of the eyes common on children alblymopia suppression of image
Loss of depth perception treat amblyopia with patching surgical correction

BS0012 (14 decks)

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