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human anatomy and physiology > vision > Flashcards

vision Flashcards

1
Q

what is sight

A

perception of objects in environment by means of the light they emit or reflect

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2
Q

name the accessory structures for vison

A

Eyebrows
Eyelids
Conjunctiva
Lacrimal apparatus
Six Extrinsic eye muscles

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3
Q

what is a sty

A

Inflamed ciliary gland of eyelash

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4
Q

what is a meibomian cyst

A

Infected oil-secreting tarsal glands

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5
Q

what is the Conjunctiva

A

Transparent mucous membrane, vascular

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6
Q

what is the Lacrimal apparatus

A

Gland & duct drain tears to nasal cavity

Tears contain bactericidal lysozyme

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7
Q

name the lacrimal structures

A

lacrimal gland (just above eye lid)
and
nasolacrimal canal (just a bit above hole of nose)

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8
Q

what do the Lacrimal gland & Nasolacrimal duct do

A

drain tears to the nasal cavity

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9
Q

how many extrinsic muscles of the eye are there

A

6

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10
Q

name the extrinsic muscles and the eye movements that they carry out

A

Superior rectus muscle:
- Upward, slightly outward

Inferior rectus muscle:
- Downward, slightly inward

Medial rectus muscle:
- Inward, toward the nose

Lateral rectus muscle:
Outward, away from the nose

Superior oblique muscle:
- Inward, downward

Inferior oblique muscle:
Outward, upward

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11
Q

describe the anatomy of the eye

A

Sphere with 3 principal components:
- Tunics: 3 layers that form wall
- Optical apparatus: admits & focuses light
- Neural apparatus: retina + optic nerve

Retina part of 1 & 3
Cornea part of 1 & 2

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12
Q

name the 3 tunics

A

Tunica fibrosa
Tunica vasculosa
Tunica interna

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13
Q

explain the Tunica fibrosa

A

sclera (white of eye) & cornea (transparent region; admits light into eye)

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14
Q

explain the Tunica vasculosa

A

uvea, under fibrosa (=choroid, ciliary body & iris)

Choroid = highly vascular, deeply pigmented layer behind retina

Ciliary body = thick extension of choroid, forming muscular ring around lens; supports iris & lens & secretes aqueous humour

Amount of melanin determines eye colour

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15
Q

explain the Tunica interna

A

retina

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16
Q

name the 3 layers of the eye (its outer surface surrounding the eye)

A

sclera (the most outer layer)
choroid
retina (most inner later of the eye layers)

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17
Q

what are the transparent elements of the eye and what are for

A

to admit/bend/focus light

  • Cornea
  • Aqueous humour
  • Lens (if cloudy = cataract)
  • Vitreous body = transparent jelly
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18
Q

where is the Aqueous Humor produced

A

by ciliary body

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19
Q

explain the Aqueous Humor in terms of what it flows through and what reabsorbs it

A

Flows through pupil into anterior chamber

Reabsorbed by ring-like blood vessel
- canal of Schlemm (= scleral venous sinus)

If reabsorption < secretion, pressure
- glaucoma

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20
Q

explain the structure of Optic Disc in Glaucoma

A

The pink rim of disc contains nerve fibers.

The white cup (in middle) is a pit with no nerve fibers.

As glaucoma advances, the cup enlarges until it occupies most of the disc area.

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21
Q

what cup to disc ratio indicated glaucoma

A

If cup to disc ratio >0.6, indicates glaucoma.

22
Q

what shape is the lens of the eye

A

curved structure
‘Ellipsoid’ in shape, 10 mm across x 4 mm front to back

23
Q

what is the crystalline lens

A

a clear disk behind the iris

flexible and changes shape to help you see objects at varying distances.

24
Q

what does the lens of the eye do

A

Bends light and focuses it for the retina to help you see images clearly.

25
Q

what happens to the eye lens as you age

A

the lens may become weaker or damaged.

26
Q

what is cataracts

A

changes in proteins (crystallins), clumping.

cloudiness vision through pupil

27
Q

explain the retina

A

Innermost layer; thin, transparent membrane

2 attachment points (optic disc & ora serrata [scalloped anterior margin])

Examine with ophthalmoscope
- Look for signs of hypertension, diabetes, atherosclerosis etc.

28
Q

explain macula lutea

A

directly posterior to centre of lens, with central fovea centralis (mostly finely detailed images); no rods, only cones; highest concentration of cones

29
Q

explain the optic disc

A

where all nerves & blood vessels pass

Creates ‘blind spot’ in vision

30
Q

what is Proliferative Diabetic Retinopathy (PDR)

A

when Irregular new blood vessels form from the retina

this can cause black patches in vision

31
Q

explain how an image is formed

A

Pupil admits light:
Diameter controlled by iris:
- Pupillary constrictor = concentric circles of SMC to narrow pupil
- Pupillary dilator = spokelike myoepithelial cells, widen pupil

Light is bent (refracted):
- By curvature of cornea towards centre of retina
- Refractive Index = measure of light retarded; lens merely fine tunes

The Near Response:
- Adjustment to close range vision

32
Q

what does changing the curvature of the lens do

A

Light from a single point of a distant object and light from a single point of a near object being brought to a focus by this changing in curvature

33
Q

what are the 3 processes involved to focus a near response image on retina

A

Convergence of Eyes:
- If problem, double vision

Constriction of Pupil:
- Screens out peripheral light rays that cannot be refracted well

Accomodation of lens:
- Change in curvature to focus

34
Q

what is near response

A

the closest an object can still be in focus.

35
Q

name some common defects of image formation

A

Hyperopia
Myopia

36
Q

what is Hyperopia

A

Image (focal plane) behind retina

Correct with convex lens

Hyperopia = “Far sighted”

Image too far, behind eyeball

Can see far objects

correctedwith convex lense

37
Q

what is Myopia

A

Image within vitreous

Correct with concave lens

Myopia = “short-sighted”

Image falls ‘short’ within eyeball

Can see near/short

38
Q

explain Sensory Transduction in Retina

A

Conversion of light energy into action potentials occurs within retina

Consider:
- Cellular layout
- Pigments that absorb light
- What happens when light is absorbed

39
Q

how many layer are there of the retina

A

5

40
Q

name the 5 cellular layers of the retina

A

Pigment cell layer – retinal (RPE) absorb light (melanin) & reduce light scatter

Photoreceptor layer
- RODS – periphery, night
- CONES – centre of eyeball, day & colour

Bipolar layer

Ganglion layer
- largest neurons of retina

Nerve Fibre layer

41
Q

what are the visual pigments in rods

A

RHODOPSIN (retinal+opsin)

(retinal is a pigment; opsin is a protein)

42
Q

what are the visual pigments in cones

A

PHOTOPSIN (retinal+~opsin)

(retinal is a pigment; opsin is a protein)

43
Q

what is retinol

A

a pigment

44
Q

what is opsin

A

a protein

45
Q

whats the shape of rods

A

long and thin

46
Q

whats the shape of cones

A

short and wide

47
Q

what is photochemical reaction

A

Cyclical process, same in rods & cones

cis-retinal (bent) absorbs photon of light, and with the requirement of ATP, it becomes trans-retinal (straight). which creates a nerve signal

trans-retinal can become cis-retinal by the dissociation from opsin

48
Q

Colour Vision is based upon what

A

Based on 3 types of cones:
Blue
Green
Red

49
Q

Perception of colour is based on what

A

on mixture of nerve signals from above

50
Q

what do people with Dichromats do

A

confuse the colours of red and green

51
Q

explain the visual pathway

A

the route of the visual image, from the retina through the optic nerve, crossing over at the optic chiasma, where the left field of vision is processed by the right side (& vice versa), moving along the optic tract to the thalamus, and on to the visual cortex (in the occipital lobe), where the brain interprets what is seen.

human anatomy and physiology (52 decks)

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