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xB12W5 > THE VISUAL SYSTEM > Flashcards

THE VISUAL SYSTEM Flashcards

1
Q

what is bitemporal hemianopia?

A

ocular defect that leads to impaired peripheral vision in the outer temporal halves of the visual field of each eye caused by damage to the optic chiasm

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2
Q

what is homonymous hemianopia?

A

a visual field defect involving either the two right or the two left halves of the visual fields of both eyes
usually caused by a brain injury

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3
Q

what is quadrantanopia?

A

A loss of vision in a quarter of the visual field. The defect is usually bilateral as it is typically caused by a lesion past the optic chiasma.

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4
Q

what is the conjunctiva?

A

a continuous, clear, thin membrane that covers the front surface of the eye and inner surface of eyelids

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5
Q

what are the 2 segments of the conjunctiva?

A

bulbar conjunctiva and palpebral conjunctiva

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6
Q

what does the bulbar conjunctiva cover?

A

sclera

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7
Q

what does the palpebral conjunctiva cover?

A

inner surface of eyelids

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8
Q

whats the function of the conjunctiva?

A

keeping eye surface moist and protected from dust, debris, infections

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9
Q

what is found within the fibrous layer of the eye?

A

cornea and sclear

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10
Q

what is the cornea and what is its function?

A

a transparent layer covering the iris and pupil, which allows light to enter the eye and refract it

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11
Q

where does the cornea get oxygen from?

A

directly from the air

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12
Q

what innervates the cornea?

A

opthamic division of trigeminal nerve

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13
Q

at what point does the cornea meet the sclera?

A

the corneal limbus

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14
Q

whats within the vascular layer of the eye?

A

iris
lens
ciliary body
choroid

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15
Q

what determines the colour of a person’s iris?

A

melanin amount

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16
Q

what are the muscles in the iris?

A

sphincter and dilator pupillae muscles - control size of pupil and therefore how much light enters the eye

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17
Q

what alters the shaoe of the lens?

A

ciliary bodies

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18
Q

what are ciliary bodies?

A

ciliary muscles and processes that connect to suspensory ligaments which are attached to the lens

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19
Q

what is the choroid?

A

the middle layer of tissue in the wall of the eye that is brown in colour so can absorb light and contains many blood vessles (between sclera and retina)

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20
Q

whats the function of the choroid?

A

supplies the outer retina with nutrients, and maintains the temperature, light regulation and volume of the eye

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21
Q

whats found in the neural layer of the eye

A

the retina

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22
Q

outline the structure of the retina?

A

has a macula which has a dense amount of photoreceptors and the fovea is in the centre of this and is where visual acuity is highest due to the most cones

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23
Q

whats within the retina?

A

ganglion cells, bipolar cells, photoreceptors

horizontal cells and amacrine cells

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24
Q

what are the 2 types of photoreceptors?

A

rods and cones

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25
Q

why is the outer layer of pigmented cells so important in the retina?

A

as it absorbs any light that doesnt hit photoreceptors to prevent scattering of light

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26
Q

whats more numerous rods or cones

A

rods

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27
Q

whats the function of rods?

A

convert visual stimuli in the form of photons (particles of light) into chemical and electrical stimuli - function best in low light

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28
Q

whats the function of cones?

A

They respond differently to light of different wavelengths, and are thus responsible for color vision, and function best in relatively bright light

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29
Q

what are the 3 chambers of the eye?

A

anterior - between cornea and iris
posterior - between iris and ciliary processes
vitreous 0 between lens and retina

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30
Q

outline the fluids in the eye?

A

anterior and posterior chambers are filled with aqueous humor
vitreous chamber is filled with vitreous humor

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31
Q

what are conjugate eye movements?

A

when eyes move in the same direction

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32
Q

what is disconjugate eye movement?

A

when eyes move in opposite direcions

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33
Q

whats an example of disconjugate eye movement?

A

vergence - adjusting the eyes for different viewing distance

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34
Q

what are examples of conjugate eye movements?

A

vestibulo-ocular
optokinetic
saccade
smooth pursuit

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35
Q

what is vestibulo-ocular eye movement?

A

a reflex acting to stabilize gaze during head movement, with eye movement due to activation of the vestibular system

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36
Q

what is optokinetic eye movement?

A

the eye to follow objects in motion when the head remains stationary

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37
Q

what is saccade eye movement?

A

rapid eye movements designed to shift the fovea to objects of visual interest.- shifting focus

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38
Q

what is smooth pursuit eye movement?

A

tracking moving objects

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39
Q

what are the 7 extraocular muscles?

A 
levator palpebrae superioris
superior oblique
inferor oblique
superior rectus
medial rectus
lateral rectus
inferior rectus
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40
Q

whats the function of levator palpebrae superioris?

A

raise the upper eyelid and to maintain the upper eyelid position

41
Q

whats the function of superior oblique muscle?

A

eye intorsion
depression
abduction

42
Q

whats the function of inferior oblique muscle?

A

elevation and abduction of the eyeball

43
Q

whats the function of superior rectus?

A

elevation
adduction
medial rotation

44
Q

whats the function of inferior rectus?

A

depression

adduction and lateral rotation

45
Q

whats the function of medial rectus?

A

adducts eyeball

46
Q

whats the function of lateral rectus?

A

abducts eyeball

47
Q

which of the extraocular muscles does the oculomotor nerve innervate?

A

superior rectus, inferior rectus, medial rectus, inferior oblique and levator palpabrae superioris

48
Q

what innervates the superior oblique muscle?

A

trochlear nerve (CN4)

49
Q

what innervates the lateral rectus muscle?

A

abducens nerve (CN6)

50
Q

whats the function of ciliary processes?

A

produce aqueous humor

51
Q

whats the function of ciliary zonules?

A

anchors the ciliary body with the lens of the eye to help maintain eye position

52
Q

whats the function of ciliary muscles?

A

accomodation - changes the shape of the lens when your eyes focus on a near object.

53
Q

what are ciliary bodies?

A

a circular structure that is an extension of the iris that contains ciliary processes and muscles

54
Q

what is miosis?

A

excessive pupil constriction

55
Q

what is mydriasis?

A

pupil dilation

56
Q

what is anisocoria?

A

when pupils are of unequal size

57
Q

how does pupil constriction occur?

A

parasympathetic control (oculomotor nerve) of iris sphincter muscles in reponse to increased light

58
Q

how does pupil dilation come about?

A

sympathetic contol of iris silator muscle in response to dim light

59
Q

where does the parasympathetic control of pupillary constriction originate?

A

in the Edinger-Westphal nucleus in the midbrain

60
Q

what nerve carries sympathetic control of pupillary dilation to the dilator pupillae muscles?

A

opthalmic nerve

61
Q

what are the 3 actions of accomodation?

A

pupil constriction
increased convexity of lens to increase refractive power
convergence
(brings near objects into focus)

62
Q

outline the accomodation reflex pathway?

A

nerve fibres travel from the occipital cortex to the front eye fields in the frontal lobe. Oculomotor nerve originates from Edinger Westphal nucleus in the midbrain and this goes on to innervate the medial rectus muscle causing convergence
it also acts on ciliary and iris sphincter muscles, causing constriction

63
Q

outline the movement of aqeous humor through the eye?

A

its produced by ciliary processes and circulates within the anterior chamber of the eye. it drains ibto the trabecular meshwork and then into schlemms canal so it can be drained into aqeous veins

64
Q

why is the fovea avascular?

A

maximizes the optical quality of the fovea pit by reducing light scattering

65
Q

where does the eyeball recieve blood from?

A

opthalmic artery and its branches

66
Q

whats the most important artery of the eye? why?

A

central retinal artery - its the onyl artery without collateral circulation
occlusion of this artery = blindness

67
Q

whats the venous drainage of the eye?

A

superior and inferior opthalmic veins which drain into the cavernous sinus

68
Q

what are the capillaries in the choroid called?

A

choriocapillaris

69
Q

whats the function of the horizontal and amacrine cells in the retina?

A

they allow information to be shared horizontally across the retina

70
Q

what are the types of cones?

A

red sensing 60%
green sensing 30%
blue sensing 10%

71
Q

which area of the eye doesnt have any photoreceptors?

A

optic dis ‘blind spot’

72
Q

what are the 3 cells in the lateral geniculate nucleus?

A

magnocellular, parvocellular and koniocellular

73
Q

outline how the primary visual cortex is topographic?

A

the central part of the visual field projects to the back of the brain and the more peripheral part of the visual field projects to a more anterior portion

74
Q

what is V1?

A

the primary visual cortex

75
Q

whats the fnction of V2?

A

to recieve information from V1 and pass it on to V3,4,5

76
Q

whats the function of V3?

A

dorsal V3 = processes motion

ventral V3 = colour sensitivity

77
Q

whats the function of V4?

A

receptive to colur, brightness and texture

78
Q

whats the function of V5?

A

receptive to motion

79
Q

what is achromatopsia?

A

partial or total absence of color vision

80
Q

what is akinetopsia?

A

motion blidness

81
Q

outline the normal apparaence of the funsu of the eye?

A

the centre is marked by the macula which will appear yellow
the macula contains a depresson called the fovea
you will be able to see arteries and veins and at the centre of these is the optic disc

82
Q

what is papilloedema?

A

swollen optic disc and vessels caused by increased ICP

83
Q

outline the visual pathway?

A

photoreceptor give impulses to retinal ganglion cells and their acons form the optic nerve
nerve enters the cranial cavity from each eye and unite at the optic chiasm. here, fibres from the medial half of each retina cross to the contralateral optic tract but lateral halves remain ipsilateral so the left optic tract contains fibres from left lateral retina and right medial retina and vice versa. each optic tract travels to its corresponding cerebral hemisphere to reach the lateral geniculate nucleus where fibres synapse and travel to the visual cortex

84
Q

what are some leadng causes of blindness?

A

age-related macular degeneration, cataract, diabetic retinopathy, and glaucoma

85
Q

what are cataracts?

A

opacification of the lens caused by protein deposition causing a painless decline in vision

86
Q

what is glaucoma?

A

increased intraocular pressure due to aqueous humor drainage pathway being blocked, causes peripheral vision loss

87
Q

what are the 3 types of glaucoma?

A

open angle - increased humor production or blocked outflow
closed Angel - narrowing of anterior chamber angle so inadequate drainage
normal tension

88
Q

what vision is lost in age-related macula degenerative?

A

loss of central vision but preservation of peripheral vision due to damage of photoreceptors in the macula

89
Q

whats the gentic basis of colour blindness?

A

recessive and x-linked so affects a lot more males!

90
Q

what is protanopia?

A

red colour blind

91
Q

what is tritanopia?

A

blue colour blind

92
Q

what is deuteranopia?

A

green colour blind

93
Q

what is protanomaly?

A

red weakness

94
Q

what is deutranomalu?

A

green weakness - have green cones so can see some shades

95
Q

what is monochromic?

A

seeing no colour

96
Q

what is tetrachromacy?

A

super colour vision

97
Q

what are dichromate?

A

a person who can only distinguish 2 colours

98
Q

what is a trachomat?

A

a person who can distinguish 3 colours

xB12W5 (7 decks)

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