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NEURO > Visual System > Flashcards

Visual System Flashcards

1
Q

Three coats of eye

A

Outer
Middle (Uvea)
Inner

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2
Q

Function of cornea

A
  • Transmission of light
  • Refraction
  • Dehydrate endothelium (no repair) - the innermost layer of the cornea, maintain corneal clarity by pumping water out
    (since water molecules alter the regular spacing between collagen fibres & cause opacity)
  • Surface Epithelium (capable of repair)- outer layer of the eye, many layers that slough off and are constantly regenerated
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3
Q

Function of Sclera

A
  • Forms the white capsule around the eye, except at its anterior surface where its specialised into clear cornea
  • Offers protection; formed of a tough outer layer of collagen
  • Serves as an insertion point for the external muscles of the eye
  • Continuation of dura mater and cornea
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4
Q

Function of Iris

A
  • Specialsed section of choroid
  • Contains and controls the size of the pupil - which lets light in
  • Sphincter muscles (circular fibres) make the pupil smaller (parasympathetic)
  • Dilator muscles (radial fibres) make the pupil larger (sympathetic)
  • Gives eyes their colour
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5
Q

Function of Ciliary body

A
  • Glandular epithelium - produces: aqueous humour and nutrients for cornea and lens
  • Aqueous humour : mainly water and electrolytes, located in the interior chamber - important in maintaining intraocular pressure (15mmHg)
  • accommodation;
    the adjustment of the lens in the eye so that clear images of objects at different distances are formed on the retina
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6
Q

Where does ciliary body receive innervation from

A

parasympathetic system

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7
Q

What is the ciliary body made from and why

A

smooth muscle which controls accommodation;

the adjustment of the lens in the eye so that clear images of objects at different distances are formed on the retina

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8
Q

Function of Choroid

A
  • Important for the nutrition of the outer retina (photoreceptors)
  • Acts as a heat sink
  • Darkly pigmented so that it can absorb stray photons
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9
Q

Function of Retina

A
  • Produces vitreous humour: which acts as a collagen scaffold, helps maintain intraocular pressure and is important in the transmission of light
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10
Q

How is the retina involved in the transmission of light

A

Light passes though the pupil from the visual field to project an image on the retina.

An object that attention is focused on, projects an image that is centred near the posterior pole of the eye along the visual axis, this point is known as the FOVEA CENTRALIS and the surrounding 1cm is known the MACULA LUTEA at these points the retina is specially modified for maximal visual acuity (resolving power)

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11
Q

Why is there a ‘blind spot’

A

Medial to macula there is region where retinal axons accumulate to leave the eye - this is the optic disc (where optic nerve forms) - no photoreceptors here = blind spot

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12
Q

whats RPE

A

RETINAL PIGMENT EPITHELIUM

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13
Q

What does RPE do

A

contains photoreceptors (rods&cones) so it is able to convert light into electric impulses (PHOTOELECTRIC TRANSDUCER) which are transmitted to ganglion cells which go on to make optic fibres an eventually the optic nerve

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14
Q

Rods

A

Important to vision in dim lighting - v sensitive to light

also important for peripheral vision

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15
Q

cones

A

colour vision

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16
Q

Tear film 3 layers:

A

1 ANTERIOR LIPID (oils) - secreted by meibomium glands, provides a hydrophobic barrier to prevent the aqueous layer evaporating

2 MIDDLE AQUEOUS (water, electrolytes & proteins) - secreted by lacrimal glands, regulates transport though the cornea and prevent infection

3 POSTERIOR MUCUS - secreted by goblet cells, provides a hydrophilic layer that allows for the even distribution of the tear film

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17
Q

ANTERIOR LIPID (oils) - secreted by

A

meibomium glands

provides a hydrophobic barrier to prevent the aqueous layer evaporating

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18
Q

MIDDLE AQUEOUS (water, electrolytes & proteins) - secreted by and does what

A

lacrimal glands

regulates transport though the cornea and prevent infection

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19
Q

POSTERIOR MUCUS - secreted by an does what

A

goblet cells

provides a hydrophilic layer that allows for the even distribution of the tear film

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20
Q

Layers through which a photon must travel though the eye (12)

A

1) Tear film (transmission)
2) Cornea (transmission and refraction - contributes o 2/3 of refraction)
3) Aqueous humour - T
4) Lens - T&R
5) Vitreous humour - T
6) Ganglion Cell -T
7) Amacrine cell - T
8) Bipolar cell - T
9) Horizontal cell - T
10) Cone - Transduction
11) Rods - Tranduction
12) Pigmented epithelium - absorption of excess photons

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21
Q

What divisions of the internal carotid artery supply the eye

A 
Ophthalmic artery 
Central Retinal artery (which passes into optic nerve)
ciliary artery 
lacrimal 
ethmoid 
eyelid artery
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22
Q

What divisions of the external carotid artery supply the eye

A

Facial Artery - supplies medial lid and orbit

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23
Q

Where is info from the eyes transmitted to?

A

Primary Visual cortex of occipital lobe

24
Q

What fields does eye receive info from

A

Temporal and nasal

25
Q

Where is primary visual cortex located

A
  • occipital lobe

- Medial surface of the hemisphere in the region above and below the calcarine sulcus

26
Q

function of the visual association cortex

A

concerned with interpretation of visual images, recognition, depth perception and colour vision

27
Q

The optic nerve carries the axons of the cells in the what layer of the retina

where do they leave the orbit

A

Ganglionic layer

leave the orbit bilaterally via the optic canal to enter the cranial cavity

28
Q

Where is the optic chiasm located

A

just anterior to the PITUITARY INFUNDIBULUM

29
Q

What do the fibres from nasal portion of the retina carry what visual fields

A

temporal visual fields

30
Q

fibres from the temproral portion of the retina carry what \ visual fields

A

nasal visual fields

31
Q

where do the optic tracts carry the fibres to terminate

A

posterolaterally around the cerebral peduncles to terminate at the lateral geniculate bodies of the thalamus

32
Q

Where do optic radiations go after the lateral geniculate body

A

Split into two
1 the fibres carrying information from the inferior portions of he retina (n thus superior visual fields) travel by looping laterally though the temporal lobe to the visual cortex known as MEYERS LOOP

2 Fibres carrying info from Superior portions of the retina (=inferior visual field) travel by looping superiorly through the Parietal lobe into the visual cortex known at BAUMS LOOP

33
Q

To remember = I’MAuditory

A

Inferior colliculus n Medial geniculate body = AUDITORY

Therefore

SUPERIOR COLLICULUS n LATERAL GENICULATE BODY = VISUAL

34
Q

Hemianopia

A

blindness over half the field of vision.

35
Q

What happens if damage to left optic nerve

A

no vision through left eye

36
Q

What happens if damage to optic chiasma

A

= no vision of temporal visual fields

37
Q

What happens if damage to right optic tract

A

no left eye temporal vision

no right eye nasal vision

38
Q

What happens if damage to Left meyers loop (=damage to superior visual field)

A

no vision in superior nasal field of left eye

and superior temporal field of right eye

39
Q

What happens if damage to left Baun’s loop (inferior visual field)

A

no vision in right eye inferior temporal field

and left eye inferior nasal field

40
Q

INTORTION

A

internal rotation towards midline

41
Q

EXTORTION

A

External rotation away from midline

42
Q

6 ocular eye muscles

A

Medial rectus

Lateral Rectus

superior oblique

inferior oblique

superior rectus

inferior rectus

43
Q

What muscles are innervated by oculomotor nerve CNIII

A

Medial rectus

Inferior oblique

superior rectus

inferior rectus

44
Q

Where is nucleus of oculomotor nerve located (CNIII)

A

periaqueductal grey near cerebral aqueduct (same as CN 4)

45
Q

What is lateral rectus innervated by

A

Abducens CNVI

46
Q

what is Superior oblique innervated by

A

Trochlear nerve CN IV

47
Q

Where is nuclei of trochlear nerve CN IV Located

A

periaqueductal grey near cerebral aqueduct (same as CN4)

48
Q

draw eye ,movement diagram

A

SR n SO intort

49
Q

Where to move eye when testing Superior rectus

A

look laterally n upwards

50
Q

Where to move eye when testing inferior rectus

A

look laterally and downwards

51
Q

Where to move eye when testing lateral rectus

A

look laterally

52
Q

Where to move eye when testing medial rectus

A

look medially

53
Q

Where to move eye when testing inferior oblique

A

look medially and upwards

54
Q

Where to move eye when testing superior oblique

A

look medially and downwards

55
Q

LR6SO4

A

Lateral rectus = cn6
superior oblique = cn4

everything else = cn3

NEURO (9 decks)

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