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AP 2
Sight & Hearing
29
Anatomy
Undergraduate 2
02/26/2017

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Term
Sight
Definition
Visual Accessory Organs: Eyelid, Lacrimal Apparatus(Tears), Extrinsic Eye Muscle, Eyelashes, Eyebrows
Term
Structure of the Eye
Definition
Hollow and Spherical Shape, 3 Layers: Outer Fibrous Tunic, Middle Vascular Tunic, Inner Nervous Tunic
Term
Iris
Definition
Composed of Connective Tissue & Smooth. Pupil is the hole inside the Iris. Dim light stimulates radial muscles and pupil dilates. Bright light stimulates circular muscles & pupil constricts
Term
Outer Tunic
Definition
Cornea(front of the eye): anterior portion, transparent, light transmission, light refraction.

Sclera(White of the Eye): posterior portion, opaque with no light, protection.

Light=waves, goes through the air in straight path. Waves will eventually bend(refraction), refraction happens through the cornea, it must refract for the fovea centralis(back of the eye)
Term
Extrinsic Eye Muscle
Definition
Superior Rectus(contracts up & medially), Inferior Rectus(rotates eye down & medially), Medial Rectus (Rotates Medially), Lateral Rectus (rotates laterally), Superior Oblique (diagonal down & lateral), Inferior Oblique (rotates up & laterally)
Term
Middle Tunic
Definition
Iris: Anterior Portion, Pigmented, Controls light intensity

Ciliary Body: no blood vessels, pigmented, holds lends, moves lens for focusing

Choroid Coat: has blood vessels, provides blood supply, melanocytes absorbs extra light, prevents glare
Term
Lens
Definition
Transparent, biconvex, lies behind the iris, largely composed of lens fibers, elastic, held in place by suspensory ligaments of ciliary body, changes shape in order to refract
Term
Ciliary Body
Definition
Forms internal ring around the front of the eye, ciliary process(radiating folds), ciliary muscles(contract & relax to move lens)
Term
Inner Tunic
Definition
Retina, contains visual receptors, continuous with optic nerve, ends just behind margin of ciliary body, composed of several layers, macula lutea- yellowish spot in retina, fovea centralis- center of macula lutea(produces sharper vision), optic disc-blind spot; contains no visual receptors, vitreous body thick gel that holds retina flat against choroid coat
Term
Visual Receptors (Rods)
Definition
Long & thin projections, contain light sensitive pigment(rhodopsin), hundred times more sensitive to light than cone, provide vision in dim light, produce colorless vision, produce outlines of objects, rhodopsin doesn't work with light & slow adjustment, decomposes with light.
Term
Anterior Cavity
Definition
Filled with Aqueous Humor.(maintains the shape), Secreted by epithelium inner surface of ciliary body, provides nutrition, leaves cavity through canal of schlemm(hole in cornea for fluid to leave and come out in tears), salt in tears can block the canal, fluid builds up causing pressure which is gloccoma.
Term
Posterior Cavity
Definition
Contains vitreous humor: thick gel that holds retina against choroid coat

Hold shape- stigmitizim(none round eye)
Term
Focusing on Retina
Definition
as light enters eye, it is refracted by:(convex surface of cornea & convex surface of lens) image focused on retina is upside down and reversed from left to right, we sense with our brains not our body.
Term
Stereoscopic Vision
Definition
Provides perception of distance & depth , results from formation of two slightly different retinal images,
Term
Visual Receptors (Cones)
Definition
short (blunt) projections, contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe(3 major clear images with light), provide vision in bright light, produce sharp images, produce color vision, focus in center
Term
Senses
Definition
General(touch & temperature): receptors that are widely distributed throughout the body

Special( hearing, taste, sight, smell): specialized receptors confined to structures in head (localized)
Term
Hearing
Definition
Ear- Organ of Hearing
3 Sections: Outer Ear, Middle Ear, Inner Ear.
Term
External Ear
Definition
Auricle(Pinnae)= collects sound waves
External Acoustic(Auditory) Meatus: lined with ceruminous glands & hairs, terminates @ tympanic membrane
Tympanic Membrane: vibrates in response to sound wave, nothing gets pass membrane
Term
Middle Ear
Definition
Tympanic Cavity: Air- Filled space in temporal bone (no water)

Auditory Ossicles: vibrate in response to tympanic membrane, parts include Malleus, Incus, Stapes

Oval Window: opening in wall of Tympanic Cavity, stapes vibrates against it to move fluids in inner ear
Term
"Eustachian Tube"- Auditory Tube
Definition
Connects the Mid Ear to the Pharynx, Helps maintain equal pressure on both sides of tympanic membrane, usually closed by valve- like flaps in the pharynx, otitis media occurs here(mid ear infection)
Term
Air Pressure(Mid Ear)
Definition
Air pressure must be equal on both sides of tympanic to properly heal, going from high to low altitude causes air pressure to be greater outside & may push tympanic membrane in, "popping" of ears occurs when pressure equalizes, opening valves may quicken process
Term
Inner Ear
Definition
3 Parts of the Labryinth(Maze):
Cochlea(snail shell): filled with fluid, functions in hearing(receptors)
Semicircular Canals: functions in equilibrium
Vestibule: functions in equilbrium
Term
Organ of Corti(Hearing Receptors)
Definition
Group of hearing receptor cells(hair), located on the upper surface of the basilar membrane, different frequencies of vibrations move different prats of basilar membrane, particular sound frequencies causes hairs of receptors to bend, nerve impulses generated, membranes between fluid when oval window vibrates to the perilymph across membranes to the endolymph, when vibration comes hair(organ of corti) bends
Term
Equilibrium
Definition
Static- stayimg same, with no body movements. This happens in the vestibule, sense of position of head when the body is not moving.

Dynamic: the balance the body uses when moving. The semicircular canals are responsible for sensing rotation & movement of the head and body
Term
Vestibule
Definition
Utricle-static equilibrium: communicates with saccule & membranous portion of semicircular canal

Saccule: communicates with the cochlear duct

Maculae: hair cells of utricle & saccule
Term
Maculae
Definition
Responds to changes in head position, bending of hairs result in generation of nerve impulse, otoliths add weight making gelatinous sheet more responsive. When moving during static equilibrium, otoliths moves to the gravity hair cells bend, and sends signals to the brain
Term
Semicircular Canals
Definition
3 Canals @ right angles

Ampulla: swelling of membranous labrynith that communicates with vestibule

Crista Ampullaris: sensory organ of ampulla, hair cells & supporting cell, rapid turns of head or body stimulates hair cells

Cerebellum receives information about bod movements and signals appriopriately to the muscle
Term
Hearing Loss
Definition
Conductive Deafness: usually temporary, interference with transmission of vibrations to inner ear, accumulated wax, changes in tympanic membrane,

Sensorineural Deafness: nerves & conduction, damage to cochlea or vestibulocochlear nerve, prolonged loud sounds, older age but to bad to repair
Term
Generations of Sensory Impulses from the Ear
Definition
1.) Sound waves enter the external acoustic meatus
2.)Causes tympanic membrane to vibrate
3.) Auditory Ossicles amplify & transmit vibration
4.) Movement of the Stapes @ oval window transmits vibrations to perilymph is scala vesti
5.) Vibrations pass through vestibular membrane & enter endolymph of cochlear duct
6.) Different frequencies of vibration in endolymph move specific regions of basilar membrane, thus stimulating certain receptors
7.) a receptor cell becomes depolarized; its membrane becomes more permeable to calcium
8.) in the prescence of calcium, vesticles at the base of receptor cells release a neurotransmitter
9.)Neurotransmitter stimulates ends of nerby sensory neurons
10.) Sensory impulses are triggered on fibers of cochlear branch of vestibulocochlear nerve
11.) auditory cortex of temporal lobe interprets the sensory impulses
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