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The Senses

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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