• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/201

Click to flip

201 Cards in this Set

  • Front
  • Back
name the 3 types of blinking
spontaneous
reflex
forced
describe spontaneous blinking
most common blink
maintains optics and comfort
what causes spontaneous blinking
palpebral portion of orbicularis
average blink rate
15 per min
reflex blinking caused by what*
sensory stimuli:

auditory
touch/irritation
dazzle
menance
touch or irritation can cause reflex blinking how
CN 5 senses it and CN 7 causes the blink
dazzle reflex blink
caused by bright lights

CN 2 senses i
CN 7 causes the blink
menace reflex blink
CN 2 senses it and begins at FRONTAL lobe

CN 7 causes the blink
forced blinking
vol forced closure do BOTH palbebral AND orbital portions of orbicularis
blinking causes what portion of tear film to be secreted
lipid secretion via holocrine method
describe what a blink does
upper lid blinks LATERAL to MEDIAl thereby SPREADING tear film over cornea and bulbar conj

MUCUS layer spread over corneal epithelium with each blink
how are tears drained
when eyes are closed tears will do the following:

puncta --> canaliculi --> lacrimal sac --> NLD --> Hasner --> IM
what does Horner's muscle do
Horner's muscle is part of orbicularis that surrounds lacrimal sac

when eye closes it contracts pumping tears into the lacrimal sac
what does the preseptal orbicularis do
contracts and stretches lacrimal sac laterally widening

tears are sucked in via the negative partial pressure that is generated
tears and optics
provide smooth surface for vision

air and tear film have great difference in n
what main thing does tear film provide to corneal epithelium via difusion
oxygen
tear film collects what that is washed away with blinking
debris
what antibacterials are located in the aqueous layer of tear film
IgA
Lysozyme
Lactoferrin
how does the tear film help provide corneal transparency
pH
osmolarity
thinnest layer of tear film
lipid <1%
role of lipid layer
prevent evaporation of aquoeus layer
primary source of lipid secretion
blinking
thickest portion of tear film
aqueous (60-70%)
role of aqueous layer
protection via proteins (antibacterials)

nutrition via glucose, water, gas exchange
aqueous contains what
urea, inorganic salts, proteins, glucose, lactoferrin, lysozyme, IgA, inerleukins
innervation of lacrimal gland
parasympathetic
sympathetic
sensory
most lacrimal gland secretions are what innervation
parasympathetic
reflex and emotional tearing come from
lacrimal gland
maintanance tearing comes from
accessory (K/W) lacrimal glands
what is the 2nd thickest layer of tear film
mucin (30-40%)
role of mucin layer
provides medium for aqueous to cover corneal epithelium
mucus secretion can be enhanced via
parasympathetic mostly and sympathetic innervation which stimulate goblet cells
how does the epthelium accept mucin and therefore aqueous layer
corneal epithelim makes glycocalyx which absorbs mucus making it the epithelium HYDROPHILIC and thus able to accept the aqueous layer
glycocalyx of corneal epithelium is important because
it absorbs mucus making the epithelium hydrophilic and thereby allowing the aqueous layer to spread over cornea
TBUT looks at what layer of tear film
lipid layer
lipids break down in TBUT because
lipids migrate down to mucus layer and contaminates it
average TBUT
5-10sec
what % of tears are lost to evaporation
25%
75% of tears are eliminated via
NL system
osmotic pressure of tears
315 mOSm/kg
what do CL do to tear film and thus osmotic pressure
increases evaporation and thereby the osmotic pressure to 330
pH of tears
7.45
what is special about the pH of tears
excellent buffers (pH 3.5-10.5)
eyedrops are mostly what type of soln
weak bases
corneal epithelium and endothelium are what
hydrophobic, lipid soluble non-inonized thus that is why eye drops are non ionized weak bases
junction found in K epithelium
tight jxns - barrier
K epithelium LS or WS
lipid soluble/non ionized

doesnt like water/ionized
K stroma is LS or WS
water soluble/ionized

doesnt like lipids
K endothelium is LS or WS
lipid soluble/non ionized

doesnt like water
what is the main source of energy for K epithelium
glucose from aqueous humor
where does K epithelium get oxygen from
diffusion from tears
where does stroma get nutrients and oxygen from
from AH via diffusion through endothelium
where does K endothelium get glucose and oxygen from
AH
what happens to epithelium when there is hypoxia
lactic acid builds up and cant cross the epithelium therefore doesnt reach stroma or endo causing edema
what allows the cornea to have minimal light scattering
spacing of collagen fibirls less the 1/2 wavelength apart to cause deconstructive interference
what maintains stromal spacing
proteoglycans (ground substance)
what are the 2 pumps of the corneal epithelium
Na/K

Na K Cl cotransporter
the Na/K pumps moves what where
K into epithelium
Na into stroma
what does the contransporter do
move K and Cl into epithelium
the movement of what ion into AH stimulates the release of Cl into tears with water following causing dehydration of cornea
K
corneal thickness is altered by moving what ion into tears
Cl then water follows
K channel responds to what changes in cornea and does what
pH
hypoxia

moves more K into AH, moves Cl and water out to tears to restore natural thickness
what ion controls thickness
K by moving itself into AH and CL/water out to tears
what happens if the epithelial BM remains intact after trauma
regeneration is fast
what happens if BM is damaged
takes months because hemidesmosomes have to be made
what is the first thing to happen when the epithelium is injured
stop basal cell mitosis
describe the regeneration process in damaged BM
basal cell mitosis stops - defected cells detach from BM and enlarge - make new hemidesmosomes btw migrated cells and BM
changes in cornea with age
ATR
increase light scatter
Descemets thickens (D3)
thinning of endothelium/density
what is autoregulation
alter resistance of vessels in order to cause a change in blood flow

flow & R inv. related
R and diameter of vessel inv related
what is responsible for autoregulation in the eye
retinal vessels
metabolic autoregulation occurs in response to what
decrease in systemic arterial pressure

retina releases metabolites to dilate vessels
myogenic autoregulation occurs in response to
transmural pressure

smooth m of bv either constrict or dilate
what structure performs autoregulation
retina
purpose of autoregulation
means in which retinal vessels get oxygen despite high IOP
critical closing pressure
pressure at which vessels collapse and blood flow stops
if IOP is too high what can happen
CRA reaches critical closing pressure and shuts down
what happens in acute angle closure attack
arterial pressure decreases and IOP increases, critical closing pressure of CRA can be reached thereby causing a CRAO leading to hypoxia in the retina and vision loss
sympathetic innervation
vasoconstriction of uvea

does not innervate CRA past lamina cribosa
parasympathetic innervation
vasodilation of anterior uvea
IOP is what in relation to perfusion pressure of retinal and uveal arteries
lower
IOP is what in relation to extravascular pressure
lower
the majority of blood flow in eye is to what
choriocapillaris
where is PO2 highest
in retina despite high blood flow in choroid
is the choriocapillaris fenestrated or tight
fenestrated to nourisg RPE and outer retina
is MAC fenestrated or tight
fenestrated
is the CB capillaries fenestrated or tight
fenestrated
is the iris capillaries fenestrated or tight
tight
is the retinal capillaries fenestrated or tight
tight
what supplies inner retina
CRA
what supplies outer retina
choroid
where are the retinal capillaries must dense
around fovea
what regions of retina are avascular
extreme periphery
center of fovea - FAZ
where does the FAZ get its blood supply
choriocapillaris
does the retina like blood
No, TOXIC to retina
name the 2 blood retinal barriers in the eye
1. tight jxn btw endothelial cells linning the retinal bv

2. btw RPE cells keeping blood from choriocapillaris out
what type of secretion is meibomian gland
holocrine
what type of secretion is goblet cells
apocrine
what is bell's phenomenom
forced eye closure causes eye to go up and out
why do dry eye patients blink a lot
to stimulate holocrine secretion of lipid from MG
which part of cornea gets oxygen from the tear film
epithelium
where does the corneal epithelium get glucose from
AH
what layers of cornea get oxygen and glucose from AH
bowman's
stroma
descemet's
endothelium
when the eye is closed how does the cornea get oxygen
lid capillaries
what happens during sleep
lid capillaries provide cornea with oxygen; corneal becomes tad hypoxic resulting in mild edema upon awakening
what does Na/K pump of epthelium do
pump Na into stroma
pump K into epithelium
what does Na/K/Cl cotransporter do
pump K & Cl into epo
K stimulates what when pH is low (acid)
Cl into tears with water following
what is 1st thing to happen after epithelial injury
stop basal mitosis
Goldmann Tonometry
measures force needed to flatten cornea

assumes all corneas have same thickness

overestimates IOP in thick corneas
underestimates IOP in thin corneas
NCT
amount of time btw initiation of air and peak response of photocell
average IOP
15.5

most ppl have >22
when is IOP highest
in morning and supine (laying on back)
what do B blockers do
block AH production by NPCE
what do alpha agonists do
constrict CB bv limiting diffusion and ultrafiltration of plasma available for making AH
what do CAI do
inhibits formation of bicarbonate
what do PG do
increase US outflow
what does pilocarpine do
increase TM outflow
what is the only cardioselective B blocker for GLC
betaxolol
what can cause decreased IOP
-decrease bp limiting available plasma for active secretion
-acidosis
-hyperosmolality
-uveitis (sick CB)
inflow and outflow must be
equal
corneoscleral (TM) route of outflow
-80%
-pressure dependent
-the more IOP the more that is drained out
what happens when IOP is too high in corneoscleral route
SC collapses and outflow into veins stops
what drains SC
episcleral veins
uveoscleral route of outflow
-20%
-pressure independent
-constant amount leaves regardless of pressure
what causes a decrease in outflow
increased episcleral venous pressure
does blood pressure affect IOP
no unless its super high
role of AH
nutrition to cornea, lens, anterior vitreous, TM

shape and protection
what is AH compared to plasma/blood
hyperosmotic
hypertonic
AH made where
NPCE
how is AH made
diffusion
ultrafiltration
active secretion
difussion
small LS particles get thru via CB fenestrations
ultrafiltration
blood plasma gets into CB via increased hydrostatic pressure
active secretion
major mech accounts for 80-90%
large WS are actively transported using energy and 2 enzymes to move Na and bicarb into PC to make AH
2 enzymes of active secretion
Na/KATPase
Carbonic Anhydrase
Na/KATPase
uses ATP to pump Na into PC with water following
Carbonic anhydrase
makes bicarb
what blocks Na/KATPase and CA
Na/KATPase - cardiac glycosides

CA- CAIs
what has more protein, AH or plasma
plasma

AH has very little protein
what has more ascorbate
AH

lens>AH>plasma
what is ascorbate
antioxidant that protects against UV
what has more Cl/aa/lactate plasma or AH
AH

tears>plasma>AH
name 3 locations of blood AH barrier
tight jnxs at:

iris vessels
SC endothelium
NPCE
afferent pupil fibers travel where
pretectal nucleus
where do afferent pupil fibers project after synapsing and passing thru pretectal
to EW to go into tectotegmental tract
what controls pupillary constriction in near reflex
frontal eye fields -- EW

bypasses pretectal
when do sympathetic fibers become postganglionic
after synapsing in SCG
what does a pancoast tumor destroy
preganglionic symp fibers that were on way to synapsing and becoming postgang at SCG
miosis when sleeping
sympathetic inhibits EW which always wants to make the pupils small, but when sleep EW is uninhibited and makes pupils small
what is lens made up of
water 2/3
protein 1/3
where is n highest in lens
nucleus
why does lens have varying n's
protein content varies in each part of lens
crystallins
proteins found in cytoplasm of lens fiber cells
alpha crystallins
act as chaperones offering resistance of degradation to other crystallins
what type of proteins are crystallins
water soluble
what happens to crystallins with age
become water insoluble leading to cataracts
what protects lens from oxidative damage
glutathione
catalase
ascorbate
calcium in lens
< than aqueous

toxic to lens leads to cataracts
blood supply of lens
avascular
where does lens get nutrients from
AH
what does the lens epithelium contain
Na/K pump
what does Na/K pump in lens do
maintains lens dehydrated
where does energy needed for Na/K pump come from
anaerobic glycolysis
enzyme that changes glucose into glucose 6 phosphate
hexokinase
glucose is converted to sorbitol via what enzyme
aldose reductase
when does glucose become sorbitol
when hexiokinase is absent
what does excess sorbitol do to the lens
accumulates in lens fibers allowing water to move into lens fibers thus causing swelling and favoring cataract formation
where are crystallins found
lens cortex
crystallins that contribute to refractive index
gamma and betta
where are insoluble proteins in lens found
nucleus
primary protector against oxidative damage in lens; transports AH and is made in lens epithelial cells and fiber cells
glutathione
prevents lens from oxidative damage; has highest concentration in lens
ascorbic acid (vit C)
what helps keep lens transparent
lens fibers dont have organelles and ae packed close together
what nerves supply lens
NONE
what happens to soluble and insoluble lens proteins with age
soluble decrease
insoluble increases
what happens to glutathione with age
decreases
what happens to Na, Ca, H2O with age
increases
what happens to nuclear fibers with age
become yellow-brown in color
what does a small pupil provide
less spherical and chromatic abberations

increase depth of field
fxn of CB
CM
makes AH
ciliary stroma provides drainage space for AH via US router
fxn of choroid
supplies outer retina
vitreous fxn
transparent unhindered medium for light passage that cushions eye and is a shock absorber

stores nutrients for retina and lens
what is the most important fxn of vitreous
stores nutrients for retina and lens
what alters the bioavailability of drugs in PC
vitreous gel
vitreous composition
water
collagen
hyaluronic acid
what does hyaluronic acid do
provides spacing and support for collagen
floaters
aggregates of collagen with age
where is collagen least located in vitreous
center
semicircular canals detect what
angular head rotations causeing reflex eye movements -- VOR
2 otoliths of ear
utricle
sacculus
what do the otoliths detect
linear head rotations causing reflex eye movemnts that are equal and opp to head motion --- linear VOR
rapid eye movemenths that maintain foveation
saccades
what controls saccades
contralateral FEF of frontal lobe
smooth tracking for slowly moving objects
pursuits
what controls pursuits
ipsilateral parietal lobe
stimulus that drives accommodation
retinal blurs
stimulus that drives vergence
retinal disparity
muscle in same eye that has secondary action that contribute to eye movement like that of agonist
synergist
muscle in same eye counteractive to agonist
antagonists
increased innervation to agonist is accompanied by corresponding decrease of innervation to antagonist
sherrington's law
what happens in primary gaze
all EOMS are contracting equally resulting in balanced centration
what happens if a muscle becomes inactive during primary gaze
eye is unbalanced and will shift in direction of antagonist