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Delta gamma VISION
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43
Anatomy
Undergraduate 2
03/15/2011

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Term
EYELID
Definition
Palpebrae.
Upper and lower.
Shades eyes during sleep.
Protects from light and foreign objects.
Spreads lubricating sections over eyes.
Term
PALPEBRAEL CONJUNCTIVA
Definition
Secretes material that lubricates the eye.
Is on the underside of the eyelid.
Term
LACRIMAL CARUNCLE
Definition
Oil and sweat glands.
Term
EYELASHES AND EYEBROWS
Definition
Protect eyes
Move and prevent substances from entering the eye.
Protect against foreign objects, perspiration.
Term
Sty
Definition
Infection of gland of follicle of eyelash.
Term
LACRIMAL APPARATUS
Definition
System containing the structures for tear production and drainage.
Term
LACRIMAL GLAND
Definition
Located in the superior lateral region of the orbital
Secretes tears.
Tears carried to conjunctiva and passed to eyeball.
Term
LACRIMAL SAC
Definition
Located in the maxilla bone.
Collects tears.
Drains into the nasal cavity.
Tears drained via duct system to nasal cavity.
Term
CRYING
Definition
Parasympathetic stimulation.
Over secretion of tears.
Term
TEARS
Definition
Protect
clean
Lubricate/moisten
surface of the eye
Term
EXTRINSIC EYE MUSCLES
Definition
6 muscles.
Move the eyeball.
Motor units are small.
Term
WALL OF THE EYEBALL
Definition
Three layers:
Fibrous tunic
Vascular tunic
Retina
Term
FIBROUS TUNIC
Definition
Outermost/superficial layer.
Two regions:
Sclera: white portion, majority, thick, gives shape/structure to eyeball.
Cornea: Clear layer, involved in focusing light, covers iris.
Term
VASCULAR TUNIC
Definition
Presence of a lot of blood vessels.
Three components:
Choroid: lines the sclera, helps with structure, contains blood vessels.
Ciliary body: secretes aqueous humor, contains smooth muscle tissue, changes lens shape, consists of ciliary processes.
Iris: Smooth muscle tissue,pigmented, consists of circular and radial smooth muscle that regulate the amount of light entering through the pupil.
Term
RETINA
Definition
Called the neural tunic.
Location of photoreceptors.
Inner lining.
Beginning of visual pathway.
Consists of pigment epithelium and neural portion.
Has optic disk and fovea centralis.
Term
OPTIC DISC
Definition
Landmark where optic nerves exit the eyeball.
Where optic nerves and bloodvessels are in contact with the eyeball.
Blind spot.
Term
FOVEA CENTRALIS
Definition
Area of highest visual activity.
Has a lot of photoreceptors.
Contains only cones.
Light is perceived best when projected on this region.
Term
PIGMENT EPITHELIUM
Definition
In the retina.
Absorbs stray light and maintains sharp image.
Term
NEURAL PORTION
Definition
In the retina.
Consists of three layers:
Photoreceptor cells.
Bipolar Neurons.
Ganglion neurons.
These three form the optic nerve.
Light passes through all three layers of the neural portion to reach the photoreceptors.
Term
TYPES OF PHOTORECEPTORS
Definition
Rods
Cones
Term
MACULA LUTEA
Definition
Exact center of the poterior of the retina.
Term
LENS
Definition
Flexible protein structure.
Avascular.
Transparent normally.
Composed of protein called crystallin.
Enclosed in a capsule.
Held in place by suspensory ligaments.
Function: fine tune focusing of light rays onto retina.
Term
HOW WE FOCUS LENS:
Definition
We change the shape of the lens.
Gets fatter or thinner depending on the distance away from the object.
Visual activity depends on flexibility of the lens.

Closer the light the longer the focal distance.
The rounder the lens the shorter the focal distance.
Term
ANTERIOR CAVITY
Definition
Area in front of the lens.
Contains aqueous humor:
watery fluid which contributes to intraocular pressure, nourishes the lens and cornea, constantly replaced.
Term
POSTERIOR CAVITY
Definition
Area behind the lens.
Contains vitreous humor:
contributes to intraorbital pressure, holds retina against choroid, formed during embryonic development, phagocytes remove debris.
Term
PHOTORECEPTORS
Definition
Sensitive to wavelengths of light.
Stimulated when light waves hit the cell.
Visual pigments inside the cell determine sensitivity.
Inner segment: nucleus and organelles.
Outer segment: in contact with pigment epithelium, named for shape of the cell, contain visual pigment.
Term
RODS:
Definition
Contain rhodospin.
Sensitive to wide rage of wavelengths.
Most active in dim light.
When stimulated we see light.
Term
CONES
Definition
Contain various pigments.
Color vision
Require more intense light to be stimulated.
When stimulated we see color.
Color blind people do not have functional cones.
Term
LIGHT
Definition
Travels as a wave.
Term
VISUAL SPECTRUM
Definition
Region of electromagnetic spectrum to which our eyes are sensitive.
Term
PHOTON
Definition
Particle measurement of light energy.
Term
VISUAL PIGMENTS
Definition
Light sensitive pigments.
Breakdown when exposed to light.
Term
RHODOPSIN
Definition
Visual pigment of rods.
Breaks down to opsin and retinal when exposed to light.
Cones have modified versions of rhodopsin.
Term
PHOTORECEPTORS IN THE DARK
Definition
Na+ channels are open.
Allows for a constant flow of calcium into the cell.
Neurotransmitter is released to inhibit bipolar cells.
No AP through the pathway.
Term
PHOTORECEPTORS IN THE LIGHT
Definition
Breakdown of rhodopsin causes Na+ channels to close.
Closing of Na+ channels stops release of neurotransmitter.
Bipolar cells not inhibited so AP is propogated to the ganglion cells and along visual pathway.
Term
ACCOMODATION
Definition
Changing the shape of the lens to focus.
As we age degree of acommodation decreases.
Term
LENS SHAPE
Definition
Ciliary muscles contracted lens rounded for close vision.
Ciliary muscles relaxed lens is flattened for distant vision.
Term
MYOPIA
Definition
Near sightedness.
Can focus close up but cant see things far away.
Can be due to flexibility of the lens or shape of the eyeball.
Term
HYPEROPIA
Definition
Less common.
Far sightedness.
Can't see up close
Due to concave nature of lens.
Eye must change shape to view things at close proximity or increase curvature of lens.
Term
PRESBYOPIA
Definition
Farsightedness due to aging.
Term
CONVERGENCE
Definition
Medial movement of the two eyeballs so that they are both directed at the same object.
Binocular vision.
Term
VISUAL PATHWAY
Definition
Optic nerve carries AP from the retina.
At optic chiasma some neurons decussate.
Each hemisphere receives AP from the medial half of view from same side and later half of field of view from opposite side
Term
VISUAL AP CONDUCTED TO BRAIN
Definition
Neurons conducted to thalamus's later geniculate nucleus.
Some to superior colliculate of midbrain (reflex activity)
Some synapse with neurons that extend to cerebrum (perceive light)
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