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!!!!! BRS YR2 !!!!! > Neuro - Visual System pt.1 > Flashcards

Neuro - Visual System pt.1 Flashcards

1
Q

Name some of the anatomical structures of the eye.

A
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2
Q

When are tears produced?

A

→ basal tear
→ reflex
→ emotional (crying)

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3
Q

What are the afferent pathways of the lacrimal system?

A

→ cornea

→ ophthalmic branch of trigeminal nerve

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4
Q

What are the efferent pathways of the lacrimal system?

A

parasympathetic

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5
Q

What is neurotransmitter used in the lacrimal system?

A

acetylcholine

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6
Q

How are tears produced and released?

A

→ tears produced by lacrimal gland
→ drain through the 2 puncta (opening on medial lid margin)
→ flow through superior + inferior canaliculi
→ gather in tear sac
→ exit tear sac through tear duct into nasal cavity

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7
Q

Where is the lacrimal gland located?

A

within the orbit, later-superior to the globe

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8
Q

What is the “basal tear”?

A

tears produced at constant level, even in the absence of irritation + stimulation

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9
Q

What is tear film?

A

thin layer of fluid that constantly covers the healthy cornea

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10
Q

How is the tear film arranged?

A

arranged in 3 layers:
→ superficial lipid layer - reduces tear film evaporation
→ aqueous tear film
→ mucinous layer corneal surface - maintains surface wetting

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11
Q

How is the superficial lipid layer produced?

A

by row of Meibomian Glands along lid margins

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12
Q

What is the purpose of the tear film?

A 
→ maintains smooth cornea-air surface
→ maintains oxygen supply to cornea (normal cornea has no blood vessels)
→ removal of debris through blinking
→ bactericide
→ maintains clear vision
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13
Q

What is the conjunctiva?

A

→ thin, transparent tissue that covers outer surface of eye
→ begins at outer edge of cornea
→ covers visible part of eye
→ lines inside of eyelids
→ nourished by tiny blood vessels (almost invisible)

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14
Q

What is the coating of the eye made up of?

A

→ sclera (hard + opaque)
→ choroid (pigmented + vascular)
→ retina (neurosensory tissue)

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15
Q

What is the sclera?

A

→ “white of the eye”
→ tough, opaque tissue
→ protective outer coat
→ high water content

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16
Q

What is the cornea?

A

→ transparent, dome-shaped window covering front of eye
→ low water content
→ powerful refracting surface, providing 2/3 of eye’s focusing power
→ like a crystal, gives clear window to look through

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17
Q

What are the 5 layers of the cornea? (EBSDE)

A

→ epithelium
→ bowman’s membrane
→ stroma - regularity contributes with transparency
→ descemet’s membrane
→ endothelium - pumps fluid out of corneal + prevents corneal oedema

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18
Q

What happens if you hydrate the cornea?

A

turns white

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19
Q

What is the uvea?

A

→ vascular coat of eyeball

→ lies between sclera + retina

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20
Q

How is the uvea arranged?

A 
composed of 3 parts:
→ iris
→ ciliary body
→ choroid
intimately connected (disease of one part affects the rest of the uvea too)
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21
Q

What is the choroid?

What are its functions?

A

→ lies between the retina + sclera

→ composed of layers of blood vessels that nourish back of eye

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22
Q

What is the iris?

What are its functions?

A

→ controls light levels inside the eye
→ round opening int he centre for pupil
→ embedded w tiny muscles that dilate + constrict pupil size

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23
Q

What is the structure of the lens?

A

→ Outer acellular capsule
→ Regular inner elongated cell fibres – transparency
→ May loose transparency with age – cataract

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24
Q

What is the function of the lens?

A 
→ Transparency
→ Regular structure
→ Refractive Power
→ 1/3 of the eye focusing power - higher refractive index than aqueous fluid and vitreous
→ Accommodation
→ Elasticity
25
Q

What is the retina?

A

very thin layer of tissue that lines the inner part of the eye

26
Q

What is the function of the retina?

A

→ responsible for capturing the light rays that enter the eye
→ light impulses are then sent to the brain for processing, via optic nerve

27
Q

What is the function of the optic nerve?

A

→ connects to the back of the eye near the macula

→ transmits electrical impulses from the retina to the brain

28
Q

What is the visible portion of the optic nerve called?

A

optic disc

29
Q

What is the blind spot?

A

part where optic nerve meets retina + there are no light sensitive cells

30
Q

What is the macula?

A

→ small + highly sensitive part of the retina responsible for detailed central vision
→ allows us to appreciate detail and perform tasks that require central vision such reading

31
Q

Where is the macula located?

A

roughly in the centre of the retina, temporal to the optic nerve

32
Q

What is fovea?

A

→ very centre of the macula
→ most sensitive part of retina
→ highest conc. of cones but lowest conc. of rods (to perceive things in detail)

33
Q

What are two parts of vision?

A

→ central vision

→ peripheral vision

34
Q

What is central vision?

A

→ Macular Vision
→ responsible for detailed central fine vision + daytime colour vision
→ reading + facial recognition

35
Q

How is central vision assessed?

A

visual acuity assessment

36
Q

What is peripheral vision?

A

→ shape
→ movement in the environment
→ night vision
→ navigation vision

37
Q

How is peripheral vision assessed?

A

visual field assessment

38
Q

What does loss of foveal vision result in?

A

poor visual acuity

39
Q

What does extensive loss of visual field result in?

A

→ unable to navigate in environment

→ patient may need white stick even with perfect visual acuity

40
Q

How many layers are in the retina?

A

3 layers:
→ outer layer
→ middle layer
→ inner layer

41
Q

What does the outer layer of the retina consist of?

A

→ photoreceptors (1st order neurones)

→ detection of light

42
Q

What does the middle layer of the retina consist of?

A

→ bipolar cells (2nd order neurones)

→ local signal processing to improve contrast sensitivity, regulate sensitivity

43
Q

What does the inner layer of the retina consist of?

A

→ retinal ganglion cells (3rd order neurones)

→ transmission of signal from the eye to the brain

44
Q

What are the two different types of photoreceptors?

A

→ rods

→ cones

45
Q

What are the main features of rod cells?

A

→ longer outer segment with photo-sensitive pigment
→ 100 times more sensitive to light than cones
→ slow response to light
→ responsible for night vision + spatial recognition
→ 120 million rods

46
Q

What are the main features of cone cells?

A

→ less sensitive to light but faster responses
→ responsible for daylight vision, fine vision, and colour
→ 6 million cones

47
Q

What is Scotopic Vision? What cells are responsible for this?

A

→ peripheral + night vision

→ rod cells

48
Q

What is Photopic Vision?What cells are responsible for this?

A

→ central vision, day light vision, colour vision, fine vision
→ cone cells

49
Q

Where are rods mostly concentrated?

A

→ widely distributed across the retina
→ highest density just outside the macula
→ density tails off towards the periphery
→ none in the macula

50
Q

Where are cones mostly concentrated?

A

only distributed within the macula

51
Q

What are the 3 different types of cone cells? What are their colours?

A

→ S-Cones : Blue (short wavelength)
→ M-Cones : Green (medium wavelength)
→ L-Cones : Red (large wavelength

52
Q

What is deuteranomaly?

A

→ most frequent form of colour blindness

→ don’t perceive the colour red

53
Q

What is achromatopsia?

A

→ full colour blindness

54
Q

How are colour vision deficits caused?

A

shift in the photo-pigment peak sensitivity

55
Q

What is the clinical name for colour vision deficits?

A

Anomalous Trichromatism

56
Q

What is anomalous trichromatism?

A

→ colour vision deficit caused by shift in photo-pigment peak sensitivity
→ results in not being able to see one or more primary RBG colours

57
Q

What is the most common form of anomalous trichromatism?

A

deuteranomaly - can’t see colour red

58
Q

What is dichromatism?

A

only two cone photo-pigment sub-types are present

59
Q

What is the condition where you experience a complete absence of colour?

A

monochromatism

achromatopsia

!!!!! BRS YR2 !!!!! (72 decks)

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