Transcript File
Visual & Auditory Systems Introduction • Five main senses of body system: sight, hearing, touch, smell, taste, • Two senses that can change life dramatically: seeing and hearing The Eyes • Images translate into impulses that create lasting memories in the mind • Three different levels of eye specialists: • Opticians make lenses • Optometrists perform eye exams • Ophthalmologists are medical doctors Anatomy of the Eye • Eyebrows shade eyes from light, particles and sweat • Eyelashes catch debris, keep eyes moist, shade the eyes • Orbit: bony socket that holds the eye • Eye position: 100 degrees peripheral vision • Eyelids: • Four layers (outer skin, muscles, connective tissue, conjunctiva) • Layers allow the eyes to open and close Anatomy of the Eye (Continued) • Conjunctiva: thin transparent layer, mucous membrane, covers eyelids and sclera • Lacrimal gland: in orbit, secretes tear into eye; has ducts to nasal cavity Anatomy of the Eye (Continued) • Cornea: transparent cover allows light into the eye • Connective tissue covered with thin epithelial layer • No blood vessels—nourished by aqueous humor (tissue fluid) and oxygen • Nerve fibers sensitive to pain Anatomy of the Eye (Continued) • Sclera: • Attached to cornea; wraps around back of eyeball • White portion of eye: many fibers and muscles with opening for optic nerve • Optic nerve sends images to brain for interpretation • Iris: colored part of eye to filter light • Vitreous humor: nourishes and cleanses eye Anatomy of the Eye (Continued) Eye Muscles and Direction of Movement • Six muscles responsible for eye movements Anatomy of the Eye (Continued) • Pupil: • Dilates (mydriasis) when focusing on distant figure or darkness • Constricts (miosis) in extreme light • Aqueous humor • provides the nutrients and oxygen to maintain lens and cornea • Accumulates; must be released to maintain pressure • Canal of Schlemm: ducts used to release aqueous humor Anatomy of the Eye (Continued) • Retina contains rods and cones responsible for vision • Rods: sight in dim light; produce black and white images • Cones: detect color • Rods and cones signals sent through optic nerve to brain • Occipital lobe—visual interpretation How the Eye Works - Video clip Rods and Cones Conditions That Affect the Eye • New developments/treatments: • Laser surgery-correct vision • Lens implantation—for blindness • Conditions: • • • • Glaucoma Conjunctivitis Congestion of eye Viral and bacterial infections Glaucoma • Pressure within the eyes is higher than normal (increased ocular pressure [IOP]) • Two causes: overproduction of aqueous humor; blocked ducts that drain excess aqueous humor • Left untreated, causes blindness • Types of glaucoma include primary, acute congestive, and chronic simple Glaucoma Conjunctivitis • • • • • “Pink eye” Common in daycare centers; contagious Acute inflammation of the conjunctiva Causes: viral, bacterial, fungal, allergies Symptoms: inflammation, itching, burning, white mucus Conjuctivitis Color Blindness • Cones: responsible for color perception • Three photopigments—identifies three colors—green, blue, red • Missing/abnormal pigment: difficult or impossible to detect colors • No treatment available Color Blindness Tests Blindness • Causes: • • • • • Accidents Cataracts Macular Degeneration Diabetic Retinopathy Glaucoma • Corneal transplant—may correct blindness Ophthalmic Agents • Ophthalmic agents aimed at controlling glaucoma, infection, inflammation, or manipulating dilation • Dosage forms: drops, suspensions, ointments, medicated disks, corrective lenses General Information • Eye solutions—keep sterile—foreign objects instilled into eyes can cause damage or infection • Patients avoid touching medication; will cause contamination • Do not instill while wearing contact lenses The Ear • Human ear responsible for hearing, balance, equilibrium, communication skills • Composed of three sections: external, middle, inner The Ear External Ear • External ear—auricle; composed of cartilage and skin; entrance for sound waves • Auditory canal: about 1 inch long; leads to tympanic membrane (eardrum) • Two major functions of tympanic membrane: protection of middle ear from foreign objects; transmission of sounds to middle ear External Ear • Sounds transmitted by vibrations • Cerumen: wax substance produced by glands Middle Ear • Vibration carried to middle ear • Cavity contains bony structures (ossicles): malleus, incus, stapes • Ossicles connected to each other Middle Ear • Eustachian tube: • Leads to nasopharynx • Equalizes pressure between outside and inside atmosphere Eustachian Tube Inner Ear • Stapes continues transfer of sound to inner ear • Fluid-filled cavity—labyrinth; comprise many components that process and transmit audible sounds via nerve impulses to brain Inner Ear (Continued) • Three main areas of the inner ear include: • Cochlea • Vestibule • Semicircular canal How the Ear works Video Conditions Affecting the Ear • Various conditions affect quality of hearing: infections, ear wax accumulation, damage to eardrum, genetic defects • Deafness—factors other than genetic abnormalities—age, inflicted damage • Loud noises break hairlike structures in middle ear; do not regenerate • No medication available—hearing aids Otitis Media • Infection of the middle ear associated with inflammation of eustachian tube • Sore throat—can lead to middle ear infection—often seen in children • Treatment: antiinfectives • Reoccurring infections—insertion of small tubes by physicians to drain middle ear Cerumen Buildup and Ototoxicity • Excessive wax builds up or dries—impedes hearing quality • Doctor removes wax buildup • Ototoxicity caused by some drugs • Tinnitus—buzzing or ringing in ears—if untreated leads to permanent ear damage • Balance may also be affected Otic Preparations • Bacterial infections treated with bactericidal or bacteriostatic preparations • All ear agents—combinations—antibiotics, steroids, ear wax removers