Exam 2: Senses - Vision Flashcards
how often do you make vitreous humor
once in your entire life - diff from aqueous humor
where do you see remnants of vitreous humor development
hyaloid canal - now t no longer has any blood vessels going through it
- used to have a purpose of nourishing the lens
conjunctiva
protects and lubricates the eye by producing mucous and tears
palpebrae
muscle that raises upper eyelid and maintains that position
lacrimal glands
secrete water and electrolytes
have enzymes and antibodies (IgA) - protect from foreign things like contacts
keeps eye moist, clears dust and debris
drains into the nasal pharynz
path of light coming into the eye
- first comes in and hits cornea - transparent part of sclera - iit starts to focus and refract light
- through the anterior chamber to the lens - majority of focusing
- thrugh posterior chamber rays are converging on fovea centralis
from corner of eye - catch more movement than detailed pictures
if up close object - what does the lens do
balls up
if far away object what does the lens do
more curved - tighten ciliary suspensory ligaments and flatten it
fovea centralis
100% cones
gives most precise clear colorful vision
away from fovea centralis you inc % of rods till the edge of your vision
100% rods
only place where retina does not cover
optic disc - blind spot
blood vessels enter and leave
optic nerve forms here
problems with the eyes and high pressure
- you are constantly making aqueous humor
- it comes from the base near where sclera and iris meet and it puts nutrient fluid over the lens goes through and comes out the scleral venous sinus - canals of schlem)
drains out through trabeculae network which can get blocked
not draining of fluid —–inc P —–glaucoma
Pressure in anterior chamber pushes posterior chamber and viitreous humor spreads P to back of eye
- if too high it can crush the receptos
cataracts
cells of lens are living
- as you feed them with aqueous humor (has sugar level since from blood)
- if diabetic and sugar level already out of control
- make excess of sorbitol in sides of lens dehydrating it causing inc P
- high sugar level on outside working to dehydrate it
- damage cells
- get opaque lens, not clear , vision looks yellowed will not see things clearly
- use laser to destroy this, suck it out and put artificial lens in
astigmatism
lens and cornea
ex: looking at spokes to see if all same shade - if not ther may be astigmatisms
pupil diameter control - what inc and dec opening
inc opening: sphincter (circular muscle fibers)
dec opening: dilator (radial fibers)
unaccommodated position
ciliary muscle relaxed
increases tension on suspensory fibers
stretch/flatten lens
distance focus
accomodation
ciliary muscle contracts
decreases tension
allows lens to become rounder
near focus
presbyopia
lose elasticity
even releasing tension does not allow rounding - lens cannot do the curvature it needs
have to move what you are looking at farther away in order to focus
parasympathetic response what fibers contract
circular fibers
sympathetic response what fibers contract
radial fibers
emmetropic
normal sized eye
myopic
near sighted eyes
length of pathway in eye is too long so yyou have rays converging on imaginary point in front of the retina - disperse before get to retina - have to correct and push the focal point back
hypermetropic
far sighted
pathway is too short, converge past the fovea centralis
pigmented epithelium
helps absorb excess light - so you do not get a glare - has no role in vision
rods
more sensitive than cones
need low level stimulation of light
in dim light - lose some of our color vision
cones
color
red: long, low energy wavelength
green: middle
blue: short high energy wavelength
what are bipolar cells influenced by
horizontal cells
horizontal cells
monitor communication between the visual receptors and the bipolar cells
can inc or dec what is happening: adjust contrast by comparing what you are looking at to the background
bipolar cells hand off info to _____ which form the –___
ganglionic cells
optic nerve
amacrine cells
monitor from bipolar cells to gangloin
involved in helping notice more differences between fields
Muller cells
like an astrocyte: keep nutrition to cells, support them, monitor ECF composition
during development help with placement migration of these cells so the are placed correctly - specific to retina
what can you blame for optical illusions
horizontal cells
2 functions of pigmented epithelium
- absorb light
- break down old discs with photosynthetic pigment
pigmented molecule
rhodopsin
opsonin molecule
embedded in it is retinol - a vitamin A derivative
retina pigmentosa - severe VA deficinecy
how does rhodopsin detect light
opsin - retinol
in dark: retinol is in cis form: bent -
when light hits: switches to trans form and it can no longer stay as part of rhodopsin so the retinol detaches from opsin and cannot go back until cis again
- the disconnection is the signal to trigger cells they have detected light
where is the difference in light sensitivity detected
opsin
difference in sensitivity between rods and cones
NOT retinol
dark current
in total darkness: receptors release glutamate so constantly seeing dark
when hit with light: dark current changes - muller cells maintain ECF and are neuroprotective against glutamate neurotoxicity
in dark making cGMP keeping Na channels open - Na comes in - glutamate release
what happens when light hits rhodopsin
it is connected to transducin and splits itactivating phosphodiesterase breaking cGMP to GMP
- since no longer cGMP it cannot keep Na channel open, no release of glutamate - no more dark current
the conversion of cis-retinol to trans-retinol releases
opsin
he centered bipolar cell is _____. off centered is _____
centered - depoolarized
off centered - hyperpolarized
on/off pattern is what establishes an image
intensity of on/off pattern is influenced by what cells
horizontal cells
macula degeneration
leading cause of blindness
mot common is “wet” as opposed to “dry”
get depth perception because of
binocular vision
optic chiasm
point of crossing for the medial portiono f optic nerve
hypothalamus
SCN branch for circadian rhythm
midbrain
superior colliculi for visual reflexes
lateral geniculate nucleus
processing point in thalamus
primary visual cortex
interprets image
