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General sense of touch

Temperature, Pressure, Pain

Special senses

Smell, sight, taste, hearing and equilibrium

70%

percentage of sensory receptors in the eye

over one million

amount of nerve fibers in the eye

Eye Protection

The eye is enclosed in a bony orbit
a fat cushion surrounds the eye

Tarsal glands

modified sebaceous glands produce an oily secretion to lubricate the eye

Ciliary glands

modified sweat glands between eyelashes

Conjunctiva

membrane that lines the eyelid and attaches to the eye; secretes mucus to lubricate the eye

Conjunctivitis

Inflammation of the conjunctiva results in redden irritated eyes; Pinkeye - viruses and bacteria

Lacrimal glands

produce fluid (diluted salt solution aka tears)

Lacrimal canals

drain tear from the eye

Lacrimal sac

provides passage for lacrimal fluid to the nasal cavity

Lacrimal apparatus

produces lacrimal fluid (tears) that contain antibodies and lysozyme; protects, moistens, and lubricates the eye, cold causes the lacrimal mucosa to swell causing watery eyes

muscles attach

to the outer surface of the eye

Fibrous Tunic

Sclera, outside layer, white connective tissue, white of the eye, contains the Cornea

Cornea

Transparent, central anterior portion; allows light to pass through; repairs easily; transplanted without rejection; no blood vessles

Choroid

Middle layer; blood rich, pigment prevents scattering light; modified internally into two structures - Ciliary Body and Iris

Ciliary Body

Smooth Muscle

Iris

Regulates light into the eye and gives the eye pigment and contains the pupil

Pupil

rounded opening of the iris through light enters

Retina

inside layer containing photoreceptors

Rods

most are on the edges; night vision; peripheral vision; all gray tones; detect motion

Cones

Detailed vision with color; most are in the middle; three types; cones are sensitive to different wavelengths

Fovea Centralis

The area of the retina with only cones ( greatest visual activity)

Color Blindness

results in the lack of one cone

Photoreceptors are not located in the?

Blind spot/ optic disc

Signals pass from photoreceptors via

the Bipolar Neurons and the Ganglion cells

Photoreceptor's signals leave through the

optic nerve

Lens

Biconvex crystal-like structure; focuses light and images onto the retina; held in place by a sespensory ligament attached to the cillary body

Aqueous Humor

Watery fluid between the lens and cornea; similar to blood plasma; maintains pressure; provides nutrients for the lens and cornea; absorbed into the venous blood through the canal of schlemm

Vitreous Humor

Gel-like substance behind the lens; keeps the eye from collapsing; is not replaced and lasts a lifetime

Accommodation

light must be focused on a point on the retina; the eye is set for distance vision (20+feet); lens must change shape to focus close objects

Eye Reflexes

the autonomic nervous system controls the internal muscles of the eye; bright light constricts pupils (radical and ciliary muscles); external muscles control eye movements (convergence)

Emmertopia

eyes focus correctly

Myopia

Nearsightedness; light rays focus in front of the retina; eyeball is too long; lens is too strong; lens is too curved; concave corrective lenses

Hyperopia

Farsightedness; light focuses behind the retina; eyeball is too short or a lazy lens; eyestrain; convex corrective lenses

Astigmatism

unequal curvatures of the cornea or lens; blurry images because light is in lines not points; require special lenses

ear houses what two senses

equilibrium and hearing

Pinna

directs sound

External auditory canal

narrow chamber, lined with skin and ceruminous glands ,in the temporal bone; ends at the tympanic membrane; conducts sound vibrations towards the ear drum

Middle ear (tympanic cavity)

air filled cavity in the temporal bone; opening to the auditory canal is covered by the typanic membrane

auditory tube

connects the middle ear to the throat; allows equalizing pressure (yawning/ swallowing/ collapsed)

Bones of the Tympanic Cavity

Malleous, Incus, Stapes; vibrations from the tympanic membrane move the malleus moving the other bones transferring sound to the inner ear

Inner Ear

filled with perilymph (plasma like fluid); bony chambers in the temporal bone - Cochlea, Vestibule, Semicircular canals

Organ of Corti

Inside the cochlea; hair cells (hearing receptors); gel like membrane lies over the hair to bend them with vibrations activate; hair stimulation sends impulses to temporal lobe through the cochlear nerve

Equilibrium

responds to movements of our head

Static Equilibrium

Maculae - receptors in the vestibule; report on the position fo the head with respect to gravity; keep our heads up; hair cells are in the otolithic membrane (jellylike membrane); otoliths (tiny stones float in gel around the hair); movement causes the otoliths to move the hair cells and send impulses to the brain

Dynamic Equilibrium

Crista ampullaris - receptor region in the semicircular canals that respond to angular or rotary movements of the head; contain tuffs of hair covered in cupula(gelatinous cap); action of angular head movements stimulates the cupula and the hair cells sending impulses through the vestibular nerve to the cerebellum

Sensorineural deafness

when there is a degeneration or damage to the receptor cells in the Organ of Corti to the auditory cortex

Conduction deafness

can still hear with bone conduction; hearing aids; build up of wax or fusion of ossioles

Chemoreceptors

Respond to chemicals in a solution

Five taste receptors

salty (metal ions), sweet (sugars, Saccharine, amino acids), bitter (alkaloids) ,sour (acids), umami (meat)

Olfactory receptors

receptors for smell - roof of the nasal cavity; neurons with olfactory hairs (cilia in the nasal epithelium); Chemical are dissolved in mucus; impulses are transmitted through the olfactory nerve to the brain where smell interpretations are made

Olfactory neurons

adapt quickly to unchanging stimuli

Taste Buds

receptor organs, tongue, soft palate, cheeks

Tongue

covered with papillae

Filiform Papillae

Sharp with no taste buds

Fungifiorm Papillae

Rounded with taste buds

Circumvallate Papillae

:Large papillae with taste buds

Taste Buds

Sides of papillae; specific receptor cells that respond to chemicals in saliva are called gustatory cells; Gustatory hairs protrude through taste pores; hairs are stimulated by chemicals in saliva

Developmental aspects of the Special Senses

Formed early as an embryo; vision is not fully functioning at birth; eye grow till age 8/9; lenses never stop growing; lacrimal glands don't fully develop till 2 weeks after birth

Presbyopia

Condition that results from decreasing elasticity of the lens as you age resulting in farsightedness

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