Chapter 15 Eyes Flashcards
What are functions of eye
shading and prevent perspiration from getting into eye
What depresses/raises the eyebrows
orbicularis muscle
What separates the eyelid/palpebrae
palpebral fissure
what protects the eye anteriorly
palpebrae (eyelids)
What are tarsal plates
CT that support eyelids internally
What is Levator palpebrae superioris
upper eyelid mobility ; raise + open eyelid
What percent of sensory receptors are in the eye
70%
What muscle moves eyebrows medially
Corrugator muscles
what are eyelashes
project from free margin of each eyelid and initiate reflex blinking
What lubricating glands are associated with eyelids
meibomian, sebaceous, and ciliary glands
conjunctivitis
inflammation of conjunctiva
what is conjunctivitis caused by
anything that can cause infection e.g daycare
WHat do lacrimal glands secrete
tears
What do tears contain
mucus, antibodies, lysozymes
where do tears enter and exit and drain
enter superolateral excretory ducts, exit medially via lacrimal punctum and drain into the nasolacrimal duct
function of tear production
keeps eyes sterile
How many extrinsic eye muscles do we have
6
which nerves innervate the eye muscles
oculomotor, trochlea, and abducens
physical look of eyeball
irregular hollow sphere
What are the 3 tunics that the wall is composed of
fibrous, vascular and sensory
What are the internal fluids between cavities
humours
What separates the internal cavity into anterior and posterior
the lens
What is colored part of eye
iris
What is center of iris where light enters
pupil
What 2 parts are part of fibrous tunic
opaque sclera and the clear cornea
WHat is the opaque sclera
white part of eye
What is the clear cornea
first place where light enters the eye and where light is refracted
What 3 origins does the vascular tunic have
choroid, ciliary, body, and iris
Describe choroid region of vascular tunic
highly vascularized, dark and brown membrane that keeps light from all scattering and supplies blood to other parts of eye
Describe ciliary body region of vascular tunic and what is it made of
thickened ring of tissue surrounding lens composed of smooth muscle/ciliary muscles
what happens to ligaments when you look close up
ligaments contract
what happens to ligaments when you look far away
ligaments relax
what happens when you get presbyopia
as you age, lens becomes less elastic; everyone gets it; very predictable
Describe the iris region of the vascular tunic
colored part of eye that includes the pupil
What is the pupil
central opening of iris
Function of pupil
regulates light entering eye during close/distant vision
T/F: Changes in emotion state can cause pupil dilation
True
Under what conditions will pupils dilate
when subject matter needs problem solving skills
Describe the retina part of the sensory tunic
2 layered membrane ; beginning of visual pathway
What is the pigmented layer of the retina
It’s called the RPE and is the outer layer in back of eye that absorbs light and prevents scattering
What does neural layer of retina contain
contains photoreceptors, ganglion cells, and amacrine and horizontal cells, bipolar cells
Function of Cones
for color vision
Function of rods
for dim light
What is order that pathway of light takes
cornea, aqueous humor, lens, vitreous humor, and the neural layer of the retina to the photoreceptors
What are the structures of the retina
ganglion cells, amacrine cell, bipolar cells, horizontal cell, rods/cones,
axons of ganglion cells go on to become what kind of nerve
optic nerves
where do ganglion cell axons run along and then leave
along inner surface of retina and leave eye as an optic nerve
What is the site where optic nerve leaves
optic disc
What is another name for optic disc
blind spot
Give an example of photoreceptors
rods and cones
Function of rods
respond to dim light and used for peripheral vision
Function of cones
respond to bright light and sharp color
where are cones located
macula lutea
Where are cones most concentrated
fovea centralis
What are the 2 blood sources of the neural retina
central artery/vein and choroid
what separates the internal eye into anterior and posterior segments
lens
What humor fills the posterior segment
vitreous (clear gel)
Functions of vitreous humor in posterior segment of internal eye
transmits light, supports surface of lens, holds neural retina against the pigmented layer, contributes to intraocular pressure
What is the anterior part of eye separated by
iris
What humor fills anterior segment
aqueous humor (waterylike)
From where does aqueous humor drain
via the canal of schlemm
Describe the attachment of the ciliary muscle (smooth muscle)
attached to ciliary process → ciliary ligaments → to lens that can change shape
if you wear contacts, where do you put it
directly over cornea
Describe the lens
biconvex, transparent, flexible, avascular structure that allows light to focus on the retina
What is the lens epithelium
anterior cells that differentiate into lens fibers
What are the Lens fibers and what are they filled with
cells filled with the transparent protein crystallin
What is the Electromagnetic radiation
all energy waves from short gamma rays to long radio waves
What is the visible spectrum
small portion of electromagnetic radiation that our eyes respond to
When does light refract/bend
when light passes from one transparent medium to another
What happens to light when it passes through a convex lens/eyes
rays converge to a focal point
How do convex lens/eyes form images (which directions) and how is it corrected
upside down and reversed right to left (but brain corrects this!)
What is the distance beyond which the lens does not need to adjust for proper focusing
20ft
How does eye accommodate for close vision
BY TIGHTENING THE CILIARY MUSCLES, ALLOWING THE P LIABLE CRYSTALLINE LENSE TO BE MORE ROUNDED
How does lens shape change when looking far away?Close?
more flattened ;close up it rounds
What are the 3 close vision requirements
accommodation, constriction, and convergence
What is accommodation and what muscle does it
The lens shape contracirng by ciliary muscles
Describe constriction and the reason it occurs
pupillary reflex constricts the pupils(prevent divergent light rays from entering the eye)
Describe convergence
medial rotation of the eyeballs toward the object being viewed
what type of lens is a concave lens
a minus lens /prescription
What type of lens is convex lens
+ lens/prescription
What is the emmetropic eye
normal eye
What is a myopic eye
nearsighted where focal point is in front of retina
How is myopic eye fixed
corrected with concave lens
What is a hyperopic eye
farsighted where focal point is behind retina
How is hyperopic eye corrected (convex or concave)
with convex lens
Define
Photoreception
process by which the eye detects light energy
Define photopigments
visual pigments
Rods v cones:which are clearer images
cones
Rods v cones:which is best suited for night vision
rods
Rods v cones:which is perceived in gray tones only
rods
Rods v cones:EACH synapses with a single ganglion cell
cones
Rods v cones:which result in fuzzy and indistinct images
rods
Rods v cones:many feeds into a single ganglion cell
rod
Rods v cones:needs bright light for activation
cones
What 2 things combine to form visual pigments
retinal molecule and opsins
What vitamin is important for vision
vitamin A
What is “bleaching”
rhodopsin breaks down into all-trans retinal + opsin
What is retinal?
light-absorbing molecule in the eye;Made from Vitamin A
What are the two forms (isomers) of retinal?
11 cis retinal (Inactive, found in the dark) and all-trans-retinal (activated by light)
What happens when light hits the rod?
11-cis retinal → all-trans retinal (shape change), Rhodopsin breaks apart (bleaching), triggers an electrical signal to the brain
What happens in darkness?
All trans retinal → back to 11-cis retinal, 11-cis retinal recombines with opsin to reform rhodopsin, Rod is ready to detect light again
What is adaption to bright light
going from dark to light
What does adaptation to light involve
switch from rod to cone function (visual sharpness is gained)
What does adaptation to dark involve
reverse operation of light adaptation; switch from cone to rod, rhodopsin accumulates and retinal sensitivity is restored
What brain structure does all sensory info go through except olfactory
thalamus
Is medial vision contralateral (with brain)/cross over and does it have lateral vision?
medial vision crosses over but not lateral vision
