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mnsr sem 2 > eye and vision > Flashcards

eye and vision Flashcards

1
Q

What is the eye?

A

sensory organ capable of converting light energy into electrical signals using photoreceptor cells

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2
Q

where is the eye found?

A

sits in a bony recess, the orbit, either side of the cranium

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3
Q

positioning and rotation of the eye is controlled by what?

A

effected by six extraocular muscles four recti and two oblique

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4
Q

How is the eye connected to the brain?

A

optic II cranial nerve innervates the muscle in such a way that the eyes normally move together/ focus on the same area

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5
Q

what is the eye composed of

A

three layers or tunics, surrounding a hollow sphere which is filled with fluids called humors

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6
Q

outermost layer of the eye (2 components)

A

fibrous layer:Composed of dense avascular connective tissue

Sclera
Cornea

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7
Q

scalera

A

white, opaque layer

Provides strength and protection to the eye as well as an attachment point for extraocular muscles

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8
Q

Cornea

A

second part of the outermost fibrous layer

transparent region of the fibrous layer, allows light to enter into the interior of the eye

provides approximately 2/3 of the human eyes focusing power

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9
Q

2nd layer into the eye

A

Uvea - Vascular tunic

contains

ciliary body

choroid

Iris

Lens

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10
Q

ciliary body

A

Ring shaped structure

containing circular and radial ciliary muscles

and the suspensory ligaments/zonule filaments

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11
Q

function of ciliary muscles in ciliary body

A

alters shape of the lens to allow for focusing on objects at different distances

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12
Q

function of suspensory ligaments/zonule filaments in ciliary body

A

attachments between the ciliary muscle and the capsule of the lens

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13
Q

function of choroid

A

Layer of blood vessels which supplies nutrients and oxygen to the retina.

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14
Q

function of iris

A

Circular ring of tissue with an opening in the centre, the pupil.

Gives the eye its colour.

Contains a circular pupillary sphincter and radial pupillary dilator muscles, which regulate the diameter of the pupil and controls amount of light entering the eye

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15
Q

structure of lens

A

basement membrane) and an inner epithelial layer. Interior of lens is packed with transparent lens fiber cells.

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16
Q

function of lens

A

Separates the humors into aqueous humor to the front and a vitreous humor behind (maintain shape)

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17
Q

3rd layer of the eye

A

Nervous/Sensory tunic, commonly known as the retina

pigmented epithelial layer, thin, and the cells contain large amounts of melanin

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18
Q

what are the two layers of retina

A

outer pigmented epithelial layer

inner light sensitive neural layer consisting of photoreceptors (modified nerve cells that detect light) and associated nerve cells

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19
Q

Aqueous humor

A

found in between cornea and the lens

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20
Q

Vitreous humor

A

found in between lens and retina

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21
Q

what is the maccula?

A

Contains large concentration of cone photoreceptor cells.

Largest density of these cells within a central area called the fovea

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22
Q

what does high density of photoreceptor cells allow for?

A

grants high-resolution, central, color vision

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23
Q

macular degeneration

A

macula Can become damaged over time,

results in loss of centrl vision

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24
Q

Optic disk

A

area in retina that is entry point for blood vessels and nerves.

Contains no photoreceptor cells, creating a “blindspot” in our vision

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25
Q

describe inner layer of the retina (3 parts)

A

composed of three types of neurons,

photoreceptors,

bipolar cells and

ganglion cells

26
Q

describe rods and cones

A

rods are slender cells and the more numerous

cones have a slightly broader body.

contain

infoldings of the plasma membrane which form stacks of membranous discs that contain the photopigments.

These discs greatly increase the light-absorbing surfac

27
Q

How many neuron types in retina?

A

5 main types of neruons

28
Q

main link between the photoreceptors and the ganglion cells

A

bipolar cells

are solely excitatory

29
Q

what do the rods and cones synapse on?

A

bipolar neurons in the retina

30
Q

what do to the bipolar neurons synapse on?

A

synapse with ganglion cells located in the retina

31
Q

optic nerve

A

The axons of the ganglion cells unite at the back of the eye in a central location

32
Q

what are the 2 lateral interneurons?

A

Horizontal cells: form connections between photoreceptor cells

Amacrine cells;form connections between bipolar cells and ganglion cells

both help process visual input within the retina

33
Q

function of ganglion cells?

A

receive signals about specific types of visual stimuli, such as colour, brightness, and motion,

and transmit this information about the characteristics of a visual image

34
Q

when do we use photopic vision

A

under bright light,

when we mainly use our color-sensitive rod cells

35
Q

when do we use scotopic vision?

A

low light environments

36
Q

when do rods work best

A

at low levels of illumination, non-functional in bright light

37
Q

what does bright light do to rod cells?

A

Photo-sensitive pigment within rod cells is degraded by bright light.

38
Q

what is the visual pigment of rods

A

rhodopsin

39
Q

what does rhodopsin consist of

A

protein opsin

co-factor 11-cis-retinal

40
Q

what causes the light sensitivity to rhodopsin

A

11-cis-retinal

41
Q

what is 11-cis-retinal derived from

A

11-trans-retinol
vitamin A

42
Q

describe the visual cycle

A

11-cis-retinal to 11-trans-retinal which generates activated rhodopsin

activated rhodopsin activates other signaling proteins, leads to generation of a signal and detection of light

Activated rhodopsin quickly breaks down into the protein opsin, releasing 11-trans-retinal

11-trans-retinal is reconverted to 11-cis-retinal by an enzyme

43
Q

how is horizontal movement in the eye controlled?

A

by the medial and lateral rectus muscles

44
Q

how is vertical movements of the eye brought about

A
45
Q

common form of color blindness?

A

distinguish between the colors red and green

46
Q

11-cis-retinal is a ___________

A

11-cis-retinal is a chromophore

47
Q

describe chemical cycle of vision

A

) Photon of light hits rhodopsin

2) Rhodopsin -> Bathorhodopsin (all trans config)
3) Bathorhodopsin>Lumirhodopsin
4) Lumirhodiopsin undergoes hydrolysis to opsin and 11-trans retinal, change causes electric signal to brain via optic nerve
5) Retinal isomerase converts 11-trans retinal –> 11-cis retinal
6) 11-cis-retinal + opsin combine to reform rhodopsin

48
Q

Choroid

A

dark membrane which absorbs stray light

49
Q

Accommodation

A

ability of the ciliary muscles to change the shape of the lens to focus objects at different distances onto the retina

50
Q

where does most of the light bending occur

A

cornea

51
Q

function of crystalline lens

A

provides additional focus for closer than 6 meters

52
Q

Near Point

A

closest distance that the eye can clearly focus on an object

53
Q

Age dependency of accommodation results from…?

A

decrease in the elasticity of the lens and a hardening of the ciliary muscles

54
Q

Different colours are encoded by different proportions of…?

A

S-, M- and L-cones

55
Q

whats responsible for direct vision

A

cones

56
Q

what causes excellent resolution

A

Each cone in the fovea centralis is connected directly to the visual cortex

57
Q

why is resolution of “rod vision” poorer?

A

many rods connected to the same nerve fibre

58
Q

where is the blind spot

A

area of the retina where the optic nerve enters the eyeball has no rods or cones present

59
Q

Stereoscopic Vision allows us to have…?

A

deapth of field

60
Q

equation for refractive power of lens

A

P=1/f= 1/u+1/v

61
Q

4 common optical defects of eye

A

Myopia=. short sightedness, can’t see far

parallel light from a distant object is focused by the relaxed eye IN FRONT of the retina

fixed by diverging (concave) lense

Hypermetropia= long-sightedness, can’t see close

Parallel light rays entering the relaxed eye are brought to a focus BEHIND the retina

Presbyopia= reduction in accommodation that occurs with increasing age;

Astigmatism= optical defect of the eye where sufferers have distorted vision due to uneven curvature of the cornea

corrected using asymmetric cylindrical lenses whose refractive power is greater in one direction than in the other

mnsr sem 2 (4 decks)

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