The Eye

Question 1

Sclera

Answer 1

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

Question 2

Cornea

Answer 2

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

Question 3

Pupil

Answer 3

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

Question 4

Iris

Answer 4

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

Question 5

Lens

Answer 5

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

Question 6

Aqueous humour and vitreous humour

Answer 6

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

Question 7

Retina

Answer 7

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

Question 8

Optic nerve

Answer 8

1.transmits electrical impulses from retina to brain
Blind spot

Question 9

Focussing light onto retina

Answer 9

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

Question 10

Focussing for distance and near viewing

Answer 10

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

Question 11

Accommodation distance and near

Answer 11

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

Question 12

Presbyopia

Answer 12

Lens harden with age
Cannot accommodate for near
Bifocal lenses

Question 13

Retina

Answer 13

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

Question 14

Choroid

Answer 14

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

Question 15

Retinal pigment epithelium

Answer 15

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

Question 16

Cones

Answer 16

Concentrated in fovea high acuity day vision and colour vision

Question 17

Rods

Answer 17

Dark vision Not present in central retina

Question 18

Horizontal cells

Answer 18

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

Question 19

Bipolar cells

Answer 19

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

Question 20

Amacrine cells

Answer 20

Interneurons connecting bipolar laterally
Inhibitory
Interact with retinal gangalion cells

Question 21

Retinal ganglion cells

Answer 21

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

Question 22

Rod cells

Answer 22

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

Question 23

cones

Answer 23

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

Question 24

Phototransduction

Answer 24

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

Question 25

Phototransduction

Answer 25

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

Question 26

Path of Phototransduction

Answer 26

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

Question 27

Lateral geniculate nucleus

Answer 27

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

Question 28

Primary visual cortex

Answer 28

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

Question 29

Depth perception.

Answer 29

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

Question 30

Visual Disease sclera

Answer 30

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

Question 31

Visual disease cornea

Answer 31

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

Question 32

Disease in pupil and iris

Answer 32

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

Question 33

Visual disease lens

Answer 33

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

Question 34

Disease in retina macular degeneration

Answer 34

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

Question 35

Retinal detachment

Answer 35

Tear allows fluid under retina risk Risk trauma family history Surgery

Question 36

Strabismus

Answer 36

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