Module 15 Flashcards by EnDea Wilkins

Name the 3parts of the eye

Outer- sclera

Middle- choroid

Inner- retina

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What are the four events of visual processing?

Refraction of light rays by lens/cornea
Conversion( turning electromagnetic into neural impulses
Transmission- AP from retina of eye to visual cortex
Perception- of visual images by primary/association areas (occipital cortex)

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What does the outer portion of the eye turn into anteriorly? (Type of lens)

He sclera turns into the CORNEA (middle layer) anteriorly

It is a non-adjustable lens

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Why is the choroid layer so important?

Lines surface or sclera and supplies blood to retina

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Name the 3 layers of the choroid part of the eye?

Choroid
Ciliary body
Iris diaphragm

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What does the ciliary body of the choroid layer do?

Adjust near/far focus (changed shape)

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What does the iris of the choroid layer do?

Work like a camera diaphragm

REGULATES light intake

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Unlike the sclera of the eye, the lens is…

And where is it located?

Adjustable!!

Behind the iris

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Which part of the eye contains the rods and cones?

The retina

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What is in the inner portion of the retina? What is in the outer portion?

Inner: cones/rods

Outer: ganglion cells

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Five neurons of the retina layer (outer to inner)

Rods/cones
Horizontal layer
Bipolar cells
Amacrine cells
Ganglion cells

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Which of the 5 neurons of the retina are the 1st order neurons? What do they form?

Ganglion

Form the optic nerve & tract

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Does cones have a high or low threshold for excitability? Why?

High Excitability because they respond to bright light.

Use: color vision, rapid vision sequencing and interpreting items

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What do rods do?

Low threshold for excitability.

Fun in dim light (night vision)

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What is the macula? Where is it located?

Important for acute detailed vision

It’s in the center of the retina

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What is the central part of the macula? What is it comprises of?

Fovea

Comprised of cones ONLY but color is optimal. HIGHEST acuity here

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Where do the optic nerves exit?

Optic disc (considered blind spot) because it has NO rods or cones

Name the six extraocular muscles

Superior rectus
Medial rectus
Lateral rectus
Inferior rectus

Superior oblique
Inferior oblique

What cranial nerve does the superior oblique muscle innervate with?

Trochlear nerve

What cranial muscle does the lateral rectus muscle innervate with?

Abducens nerve

What cranial nerve do the other four extraocular muscles innervate with?

Oculomotor nerve

Where are the nuclei of the CN that serve the eye located?

III & IV- midbrain

VI- pons

Which ganglion is the sensory ganglion for the visual system?

The ciliary ganglion

Lesions to the brainstem can cause?

Visual, hearing, balance and speech impairments AT THE SAME TIME

Name the 3 visual fields and what they see?

Binocular (what's seen by both eyes) Monocular (seen by one eye) Macular (central vision from both eyes) **remember this is in the center of the retina**

What are the names of the visual half fields?

Temporal (lateral half) Nasal (medial half)

What are the two hemi-retinas and where do they get info from?

Temporal projects to nasal hemi retina Nasal projects to temporal hemi retina

Where is the optic chaism located? What happens here?

Just rostral (top) to hypothalamus Fibers from nasal retinas CROSS HERE Temporal retinas DO NOT cross (ipsilateral)

How do the visual cortex receive data?

Left eye: Nasal visual field from left eye Temporal visual field from right eye Right eye: Nasal visual field from right eye Temporal visual field from left eye

What is the optic tract?

Pathway from chaism to lateral geniculate body of thalamus

What is the lateral geniculate body?

2nd order neurons! Travel in optic radiation bundles to primary visual cortex (area 17)

What part of the internal capsule so the pathways for vision pass through?

Posterior limb

Where does the data from the upper visual field go?

Lingual gyrus (below the calcarine sulcus)

Where does the data from the lower visual field go?

To the cuneus gyrus (above the calcarine fissure)

Is the upper visual field considered the upper retina?

NO! It is the lower retina because the lens inverts the data before sending it to the retina

The lower retina is the upper visual field (T/F)

True

How do you asses visual fields?

Use visual perimetry- assess areas of blindness in visual space

How is loss of vision described?

In reference to visual fields

What is monocular blindness?

Blindness in one eye

What is Hemianopsia?

Loss of a visual half-field

What is quandrantanopsia?

Loss of a visual quandrant