NS 13: Vision

Physician Assistant Pa 2013 Session 1 with Tsai at Touro University (NV)

About this deck

By: John Yaw-Jong Tsai
Created: 2011-10-09
Size: 16 flashcards
Views: 0

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What is the loss of accommodation reflex called?

prebyopia

accommodation reflex diminishes with age

reading glasses

What is hyperopia and myopia?

hyperopia = far sighted

myopia = short sighted

How many rods per eye approx.?

130 million per eye approx.

rods contain rhodopsin (vit A)

see in dark (no vit A = night blindness)

Rods and cones - which one sees color?

cones see color

have iodopsin

Why are red/green color blindness more common in males?

because red and green on X-chromosome

L-cone = red
M-cone = green
S-cone = blue

What makes up rhodopsin?

rhodopsin = opsin + retinal

in dark, retinal binds to opsin

What happens to rods in the dark?

in dark, retinal binds to opsin
cGMP is high - keeps cGMP gated channel open for Na+ and Ca2+
photoreceptors do not fire action potentials (kept at -40mV)
keep releasing Nt to bipolar cells

What happens when photon strikes rods?

photon strikes rod - retinal unbind from opsin
activates transducin - closes cGMP gated channel
cell now hyperpolarizes and Nt release is decreased

What is a fovea?

small depression in retina, surrounded by macula lutea

consists entirely of cones

What is the macula lutea?

area surrounding fovea (yellowish appearance)

ganglion cells and retinal surface vessels are absent from this area

avoids blocking light entry

Differentiate between glaucoma and papilledema

glaucoma
increased pressure in fluid chamber of eyes

papilledema
blockage of flow from retinal veins

What is the nucleus for visual pathway?

lateral geniculate nucleus

project to visual cortex in a retinotopic organization

Pupillary light reflex involves which nuclei/nerves?

brainstem - pretectum
↓
oculomotor nerve nucleus
↓
CN III - oculomotor
↓
ciliary ganglion

If optic nerve of one eye has been disrupted, what would happen to if light was shone in damaged eye?

light in damaged eye would not produce constriction in any eye

light in good eye will cause constriction in both eyes
due to ciliary ganglion reflex not going through optic nerves

As long as optic pathway for reflex is still intact, uninjured eye will still respond. T/F?

true

if lesion is in reflex pathway of one eye, shining into the damaged reflex eye will produce a constriction in good eye, but shining in good eye will not produce a reflex in bad eye

indicative of location of brain damage

How are eye movements associated with vestibular system?

vestibular eye movements

keeps eye focused as head turns or changes orientation in space

About this deck

By: John Yaw-Jong Tsai
Created: 2011-10-09
Size: 16 flashcards
Views: 0

About StudyBlue

“I have been getting MUCH better grades on all my tests for school. Flash cards, notes, and quizzes are great on here. Thanks!”
Kathy