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Neuro > Visual System > Flashcards

Visual System Flashcards

1
Q

Why do we have 2 eyes

A

Stereopsis = able to see in 3D
Widens our visual field

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2
Q

Number of layers of the eye

A

3

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3
Q

3 layers of the eye

A

Outer layer = sclera and cornea
Middle layer = uvea
Inner layer = retina

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4
Q

Sclera

A

Tough fibrous outer coat
Made of collagen

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5
Q

Why must the outer layer of the eye be transparent - cornea

A

Light transmission

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6
Q

Why must the outer layer of the eye be tough

A

Barrier to trauma and infection
Maintains shape of eye

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7
Q

What is the cornea and sclera made out of

A

Collagen

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8
Q

Outer layer of eye and refraction

A

Responsible for 2/3 refractive power of eye

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9
Q

Number of layers in outer layer of eye

A

5

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10
Q

5 layers of outer layer of eye

A

Epithelium
Bowman’s layer
Stroma
Descemet’s layer
Endothelium

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11
Q

What makes up the middle layer of the eye

A

Iris
Ciliary body
Choroid

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12
Q

Iris

A

Coloured part at front of eye
Contains dilator and sphincter pupillae muscles (pupillary reflexes)

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13
Q

Ciliary body

A

Glandular epithelium produces aqueous humour
Ciliary (smooth) muscle controls accommodation

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14
Q

Choroid

A

Blood supply to outer third of retina
Heat sink
Darkly pigmented so that it can absorb stray photons

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15
Q

Retina

A

Specialised organ of phototransduction

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16
Q

What makes up the retina

A

Macula lutea
Fovea centralis
Cones
Rods

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17
Q

How are collagen fibres laid out in sclera

A

Cross-linked creating opacity

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18
Q

How are collagen fibres in cornea laid out

A

Parallel - transparent

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19
Q

What percentage of outer layer if cornea

A

1/6 (continuation of sclera)

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20
Q

Limbus

A

forms the border between the transparent cornea and opaque sclera, contains the pathways of aqueous humour outflow, and is the site of surgical incisions for cataract and glaucoma

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21
Q

Where are stem cells for the cornea found

A

Limbus

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22
Q

What causes the choroid to be coloured

A

Contains melanocytes-

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23
Q

Ora serrata

A

serrated junction between the retina and the ciliary body. This junction marks the transition from the simple non-photosensitive area of the retina to the complex, multi-layered photosensitive region.

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24
Q

Intraocular lens

A

Suspended from cornea
1/3 refractive power

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25
Q

Which part of the eye never stops growing

A

Lens

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26
Q

Presbyopia

A

gradual loss of your eyes’ ability to focus on nearby objects.
It’s a natural, often annoying part of aging.
Presbyopia usually becomes noticeable in your early to mid-40s and continues to worsen until around age 65

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27
Q

What percentage of the corneal depth is the stroma

A

90%

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28
Q

Which layers of the outer layer of the eye can regenerate

A

Epithelium (not endothelium)

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29
Q

Role of endothelium in cornea

A

Keeps it dehydrated - fluid removed to keep it clear
Water actively pumped out of stroma so transparent

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30
Q

Thickness of cornea

A

550 micrometers

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31
Q

Role of ciliary muscles

A

Holds lens in place by suspensory ligaments
Contract/relax to control accommodation of lens

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32
Q

Function of iris

A

Changes aperture of pupil

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33
Q

What fluid fills the anterior chamber of the eye (between cornea and iris)

A

Aqueous humour

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34
Q

What produces the aqueous humour

A

Ciliary bodies

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35
Q

Function of aqueous humour

A

Maintain pressure in eye

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36
Q

Anterior chamber of eye

A

Between cornea and iris

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37
Q

Posterior chamber of eye

A

Between iris and ciliary processes

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38
Q

Pigmented outer layer of retina

A

formed by a single layer of cells. It is attached to the choroid and supports the choroid in absorbing light (preventing scattering of light within the eyeball). It continues around the whole inner surface of the eye.

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39
Q

Neural inner layer of retina

A

consists of photoreceptors, the light detecting cells of the retina. It is located posteriorly and laterally in the eye.

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40
Q

Macula lutea

A

part of the retina that is responsible for sharp, detailed central vision (also called visual acuity)
Very high concentration of cones

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41
Q

Sphincter muscles

A

Make pupil smaller
Parasympathetic

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42
Q

Dilator muscles

A

Make pupil larger
Sympathetic

43
Q

Intraocular pressure

A

15 mmHg

44
Q

Pars plana

A

Located near iris-sclera junction

45
Q

Keratoconus

A

Abnormal shaped cornea
Results in a stigmatism and distorted light and visual focus

46
Q

Coloboma

A

Left without uvea
Results in field defect in the affected area

47
Q

Clinical links to retina

A

Central scotomas
Night blindness
Macular degeneration can lead to blindness
Humours - open angle glaucoma
Tunnel vision affects 2% of population

48
Q

Vitreous humour

A

Acts as a collagen scaffold and helps maintain Intraocular pressure

49
Q

What produces the vitreous humour

A

Retina

50
Q

Fovea centralis

A

When light passes through pupil it projects an image of what you’re focused on to the fovea centralis

51
Q

Retinal pigment epithelium

A

Contains photoreceptors (rods and cones)

52
Q

Rods

A

Dim lighting
Sensitive
Peripheral vision

53
Q

Cones

A

Colour vision

54
Q

Photoelectric transducer

A

Converts light into electric impulses

55
Q

Number of layers of tear film

A

3

56
Q

3 layers of tear film

A

Anterior lipid
Middle aqueous
Posterior mucous

57
Q

Anterior lipid layer

A

Secreted by meibomium glands
Provides hydrophobic barrier to prevent aqueous layer evaporating

58
Q

Which glands secrete anterior lipid layer

A

Meibomium gland

59
Q

Middle aqueous layer

A

Water, electrolytes and proteins
Secreted by lacrimal glands
Regulates transport through cornea and prevents infection

60
Q

Which glands secrete middle aqueous layer

A

Lacrimal glands

61
Q

Posterior mucous layer

A

Secreted by goblet cells
Provides hydrophilic layer
Allows for even distribution of tear film

62
Q

Which cells secrete posterior mucous layer

A

Goblet cells

63
Q

What does the vitreous humour contain

A

Hyaluronic acid and water

64
Q

Blood supply to eye

A

Internal carotid artery- ophthalmic artery, central retinal artery and ciliary arteries
External carotid artery - facial artery supplies medial lid and orbit

65
Q

Branches of internal carotid artery that supplies eye

A

Ophthalmic
Central retinal
Ciliary

66
Q

Photon pathway

A

Tear film (transmission)
Cornea
Aqueous humour
Lens
Vitreous humour
Ganglion cell
Amacrine cell
Bipolar cell
Horizontal cell
Cone
Rods
Pigmented epithelium (absorption of excess photons)

67
Q

Hypermetropia

A

Underpowered to focus near objects on retina
May be due to:- corneal curvature too shallow- lens not flexible enough- axial length of eyeball too short

68
Q

Myopia

A

Overpowered so can’t focus far objects on retina
May be due to:- corneal curvature too steep- axial length of eyeball too long

69
Q

Adenexae

A

Tear film
3 layers anterior lipidmiddle aqueousposterior mucous
Protective
Nutrition for cornea

70
Q

Which veins drain the choroid

A

Vortex veins

71
Q

Where do superior ophthalmic veins drain into

A

Cavernous sinus

72
Q

Where do inferior ophthalmic veins drain into

A

pterygoid venous plexus

73
Q

Lymphatics.

A

No lymphatic drainage of globe
Conjunctiva and lids drain into submandibular and pre-auricular nodes

74
Q

Extra cranial visual pathway

A

Optic nerve formed by convergence of axons from retinal ganglion cells
Receive impulses from rods and cones
Optic nerve leaves via the optic canal through sphenoid bone
Enters the cranial cavity and runs along the middle cranial fossa

75
Q

Intracranial visual pathway

A

In middle cranial fossa, optic nerves join = optic chiasm
At chiasm, fibres from the medial halves cross to the contralateral optic tract
Fibres from the lateral halves remain ipsilateral
Optic tracts then travel to lateral geniculate nucleus in the thalamus and fibres synapse

76
Q

Where do optic tracts synapse

A

Lateral geniculate nucleus in thalamus

77
Q

Optic radiation

A

Carry visual information to visual cortex from lateral geniculate nucleus

78
Q

Upper optic radiation

A

Carries fibres from superior retinal quadrants (Baumans loop)
Travels through parietal lobe to visual cortex

79
Q

Which optic radiation travels through the parietal lobe

A

Upper optic radiation

80
Q

Lower optic radiation

A

Carries fibres from the inferior retinal quadrants
Travels through temporal lobe (via Meyer’s loop) to visual cortex

81
Q

Which optic radiation travels through the temporal lobe

A

Lower optic radiation

82
Q

Superior retinal quadrants correspond to

A

Inferior visual field quadratns

83
Q

Inferior retinal quadrants correspond to

A

Superior visual field quadrants

84
Q

Intorsion

A

Internal rotation

85
Q

Extortion

A

External rotation

86
Q

6 ocular muscles

A

Medial rectus
Lateral rectus
Superior oblique
Inferior oblique
Superior rectus
Inferior rectus

87
Q

Damage to left optic nerve causes

A

No vision in left eye

88
Q

Damage to optic chiasm

A

Loss of vision of the temporal visual fields = hemianopia

89
Q

Damage to left optic tract

A

Loss of vision of temporal field of left eye and nasal field of right eye

90
Q

Damage to left Meyer’s loop

A

Loss of vision in superior nasal field of left eye and superior temporal field of right eye

91
Q

Damage to Baum’s loop

A

Loss of vision in inferior temporal field of right eye and inferior nasal field of left eye

92
Q

Meyer’s loop

A

Lower optic radiation through temporal lobe

93
Q

Baumans loop

A

Upper optic radiation through parietal lobe

94
Q

Outer segments of rods and cones

A

contains discs containing light sensitive photopigment

95
Q

Inner segments of rods and cones

A

made up of cell body, axon and synaptic terminals

96
Q

Photopigment in rods

A

Rhodopsin

97
Q

Photopigment in cones

A

Opsin

98
Q

Opsins

A

transmembrane proteins which contain the light sensitive molecule retinal
Different opsin structures mean retinal absorbs different wavelengths of light

99
Q

Effect of a photon on a rhodopsin molecule

A

Triggers conformation change to all-trans form
This change triggers changes in the opsin structure
This in turn triggers a cascade within the cell

100
Q

Signals in the retina

A

Photoreceptor → bipolar cell → retinal ganglion cell
Horizontal and apocrine cells modulate signal
Retinal ganglion cells not graded response – action potential

101
Q

Retinal blood supply outer 1/3

A

Choroid (posterior ciliary arteries)

102
Q

Retinal blood supply inner 2/3

A

Central retinal artery

103
Q

The visual pathway begins with the retina sending signals down the optic nerve towards the optic chiasm. After the optic chiasm, the optic tracts carry on the signal reaching the lateral geniculate nuclei. After this both the meyers loop and baums loop (optic radiations) carry the signal to the visual cortex. Lesions at any point in this pathway are known to cause various visual defects.
Which lobe does Baums loop pass through?

A

Parietal

104
Q

The visual pathway begins with the retina sending signals down the optic nerve towards the optic chiasm. After the optic chiasm, the optic tracts carry on the signal reaching the lateral geniculate nuclei. After this both the meyers loop and baums loop (optic radiations) carry the signal to the visual cortex. Lesions at any point in this pathway are known to cause various visual defects.
Which lobe does meyers loop pass through?

A

Temporal

Neuro (22 decks)

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