Unit 8 - Vision Anatomy Flashcards

1
Q

Where does the pathway for vision travel

Lesion of what vessel affects vision

A

Length makes it susceptible to demyelination

NB - vascular lesions in posterior cerebral artery

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2
Q

4 cells involved in conduction of visual impulses to visual cortex

A

Photoreceptor cells - rods and cones

Bipolar neurons - connect rods and cones to ganglion cells

Ganglion cells - whose axons pass to thalamus

Neurons of LATERAL geniculate body in thalamus - axons pass to visual cortex

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3
Q

Layers in retina

A

Outermost layer = pigment epithelial layer

Single layer of cells containing melanin

Pigment cells absorb light that passes through retina

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4
Q

Difference between rods and cones

A

110-125 million rods

6-7 million cones

Cones - colour

Rods - low intensity light - contain melanin

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5
Q

What is the fovea

Name the area surrounding it

What is found in the floor of the fovea

A

the retina is structurally different at fovea

bipolar and ganglion cells lean away from a central pit

Area surrounding it = macula lutea (yellow)

Only cones found in fovea

Inner retinal layers are displaced to allow light rays to reach cones without having to cross other layers - point of most acute vision as it is the visual axis

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6
Q

Blind spot of the eye

A

Optic disc - papilla

area at which unmyelinated optic nerve fibres exit the retina

Fibres become myelinated as they emerge

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7
Q

What does the retina develop from during development

A

From CNS

Optic nerve is a CRANIAL nerve but is myelinated by oligodendrocytes - cannot regenerate when damaged

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8
Q

Pathway of visual impulses

A

Rods and cones → bipolar cells → retinal ganglion cells → optic nerve → optic chiasm → thalamus → visual cortex

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9
Q

What axons make up the optic nerve

A

Axons of retinal ganglion cells from the optic nerve which passes through the optic canal

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10
Q

Describe binocular vision

A

Right and left fields of vision are projected on portions of both retina

Visual fields overlap across 2/3rds of total visual fields

right visual cortex sees left visual field

only 1/2 cross in optic chiasm

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11
Q

Image of right field of vision projected onto

A

Nasal half of right retina

Temporal half of left retina

Right visual field → left visual cortex

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12
Q

How do fibres travel in optic tract

A

Fibres from nasal/medial retina cross midline and enter optic tract of opposite side

Fibres of temporal/lateral retina pass posteriorly in optic tract of same side

Most fibres terminate in lateral geniculate nucleus

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13
Q

Where is the primary visual cortex found

A

Walls of calcarine sulcus

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14
Q

What do lateral geniculate neurons give rise to

A

Optic radiation (loop of meyer)

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15
Q
A
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16
Q

Broadmans area of visual cortex

A

BA 17

17
Q

Visual field quadrants

A

Visual filed quadrants projected onto retina in reversed and inverted pattern through action of lens

Preserved all the way to visual cortex

Axons and cortex responsible for visual field of right eye - in the gaps

18
Q

Where is the optic chiasm in close relation to

A

Stalk of pituitary - pituitary tumour may damage median portion of chiasm

19
Q

Effect of aneurism in circle of willis

A

Impacts optic chiasm

20
Q

Pathway of light reflexes

A

Some fibres of optic tract pass from lateral geniculate nucleus to pretectal nucleus of midbrain (concerned with light relfexes)

21
Q

Proportion of fibres that travel to pretectal nucleus

A

As the optic tract approaches the thalamus it winds around the midbrain - medial and lateral route

Majority of fibres will terminate in lateral geniculate bodies (lateral route)

Medial route - 10% - enters side of midbrain - enter pre-tectal nucleus and serve as papillary light reflex

22
Q

Direct vs consensual light reflex

How does the impulse travel

A

Light shone on 1 eye - pupils of both eyes constrict

Constriction of pupil in eye in which light is shone - direct light reflex

Constriction of opposite pupil - consensual light reflex

Impulse travels through optic nerve → optic chiasma → optic tract → synapse on nerves in pretectal nucleus (close to superior colliculus)

23
Q

Where do light reflexes travel

A

Pass to PS nuclei of CN III (occulomotor)

Edinger-Westphal nuclei on both sides - posterior commissure

Impulses pass through CN III to ciliary ganglion in orbit - to short ciliary nerves at eyeball - constrictor pupillary muscle of iris

both pupils constrict

24
Q

Where does the sympathetic nucleus of vision lie

A

Within tegmentum of midbrain

25
Q

What nerves are responsible for controlling extraocular muscles

What opening do they pass through

A

CN IV - trochlear

CN VI - abducent

CN III - oculomotor (majority)

Superior orbital fissure

26
Q

Abducent

A

Lateral rectus muscle

Abduction

27
Q

Trochlear

A

Superior oblique

Intorsion & elevation

28
Q

Oculomotor nerve

A

Superior rectus - elevation & intorsion

Inferior rectus - depression & extorsion

Inferior oblique - extorsion & depression

29
Q

Superior oblique

A

Elevation & intorsion

CN III

30
Q

Inferior rectus

A

Depression & extorsion

CN III

31
Q

Medial rectus

A

Adduction

CN III

32
Q

Lateral rectus

A

Abduction

CN VI

33
Q

Superior oblique

A

Intorsion & elevation

CN IV

34
Q

Inferior oblique

A

Extorsion & depression

CN III

35
Q

Muscles of the eye

A
36
Q

Movements of eye

A