Module 15 Flashcards
Name the 3parts of the eye
Outer- sclera
Middle- choroid
Inner- retina
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)
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
Why is the choroid layer so important?
Lines surface or sclera and supplies blood to retina
Name the 3 layers of the choroid part of the eye?
Choroid
Ciliary body
Iris diaphragm
What does the ciliary body of the choroid layer do?
Adjust near/far focus (changed shape)
What does the iris of the choroid layer do?
Work like a camera diaphragm
REGULATES light intake
Unlike the sclera of the eye, the lens is…
And where is it located?
Adjustable!!
Behind the iris
Which part of the eye contains the rods and cones?
The retina
What is in the inner portion of the retina? What is in the outer portion?
Inner: cones/rods
Outer: ganglion cells
Five neurons of the retina layer (outer to inner)
Rods/cones Horizontal layer Bipolar cells Amacrine cells Ganglion cells
Which of the 5 neurons of the retina are the 1st order neurons? What do they form?
Ganglion
Form the optic nerve & tract
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
What do rods do?
Low threshold for excitability.
Fun in dim light (night vision)
What is the macula? Where is it located?
Important for acute detailed vision
It’s in the center of the retina
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
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
