Visual & Auditory Systems. Introduction Five main senses of body system: sight, hearing, touch,...

Visual & Auditory Visual & Auditory SystemsSystems

IntroductionIntroduction• Five main senses of body system:

sight, hearing, touch, smell, taste,

• Two senses that can change life dramatically: seeing and hearing

The EyesThe 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 EyeAnatomy 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 Anatomy of the Eye (Continued)(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 Anatomy of the Eye (Continued)(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 Anatomy of the Eye (Continued)(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 Anatomy of the Eye (Continued)(Continued)

Eye Muscles and Direction of MovementEye Muscles and Direction of Movement

• Six muscles responsible for eye movements

Anatomy of the Eye Anatomy of the Eye (Continued)(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 Anatomy of the Eye (Continued)(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 ConesRods and Cones

Conditions That Affect the EyeConditions 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

GlaucomaGlaucoma

• 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

GlaucomaGlaucoma

ConjunctivitisConjunctivitis

• “Pink eye”

• Common in daycare centers; contagious

• Acute inflammation of the conjunctiva

• Causes: viral, bacterial, fungal, allergies

• Symptoms: inflammation, itching, burning, white mucus

ConjuctivitisConjuctivitis

Color BlindnessColor 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 TestsColor Blindness Tests

BlindnessBlindness

• Causes:• Accidents• Cataracts• Macular Degeneration• Diabetic Retinopathy• Glaucoma

• Corneal transplant—may correct blindness

Ophthalmic AgentsOphthalmic Agents• Ophthalmic agents aimed at

controlling glaucoma, infection, inflammation, or manipulating dilation

• Dosage forms: drops, suspensions, ointments, medicated disks, corrective lenses

General InformationGeneral 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 EarThe Ear• Human ear responsible for

hearing, balance, equilibrium, communication skills

• Composed of three sections: external, middle, inner

The EarThe Ear

External EarExternal 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 EarExternal Ear• Sounds transmitted by vibrations

• Cerumen: wax substance produced by glands

Middle EarMiddle Ear• Vibration carried to

middle ear

• Cavity contains bony structures (ossicles): malleus, incus, stapes

• Ossicles connected to each other

Middle EarMiddle Ear

• Eustachian tube:

• Leads to nasopharynx

• Equalizes pressure between outside and inside atmosphere

Eustachian TubeEustachian Tube

Inner EarInner 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 Inner Ear (Continued)(Continued)

• Three main areas of the inner ear include:• Cochlea• Vestibule• Semicircular canal

How the Ear works Video

Conditions Affecting the EarConditions 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 MediaOtitis 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 OtotoxicityCerumen 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 PreparationsOtic Preparations

• Bacterial infections treated with bactericidal or bacteriostatic preparations

• All ear agents—combinations—antibiotics, steroids, ear wax removers