Chapter 20 SENSORY SYSTEM

Receptors specializing perceiving change from internal & external environment  Environmental  Vision  Hearing  Touch  Taste  Smell  Position  balance  Organs  Eye  Ear  Tongue  Nose  skin FUNCTION

 Receive 90% environmental information  Blinking-reflex to protect  Conjunctiva-protects & lubricates  Lacrimal duct-tears  1/5 th of eye external EYES

 Sclera-supports & gives structure  Cornea-focuses light to retina  Choroid, iris, & ciliary muscles-provide blood supply  Iris & ciliary muscles-intrinsic muscle  Eyeball  Not solid  Anterior cavity  Clear watery fluid-aqueous humor  Posterior cavity  Semisoft gelatin-vitreous humor  Both cavities help maintain shape EYES

 Pupil  Black part  Iris  Round, colored muscle  Contracts/relaxes to allow for light  Lens  Convex, transparent tissue  Focuses & directs light to retina EYES

Refraction Refraction Lens bends light to focus on the retina. Lens bends light to focus on the retina. Accommodation Accommodation lens changes shape focusing near & far. lens changes shape focusing near & far. Converge Converge Creates one object to see Creates one object to see VISION IS SIMILAR TO A CAMERA.

EYES  Rods  Sensitive to dim light  100 million rods  Cones  Sensitive to bright light  Color distinction  Green  Red  blue  Impulses transmitted to brain by optic nerve 

 Functions  Hearing  Equilibrium  Men listen with left side of brain  Women use both sides. EAR

 Pinna  Collects & transmits sound waves  Tympanic Membrane  Separates outer & middle ear  AKA eardrum  Cerumen  AKA ear wax  Protects from FB EXTERNAL EAR

 Air filled chamber  Tympanic membrane  Changes sound waves to mechanical movements  Bones  Hammer (malleus)  Anvil (incus)  Stirrup (stapes)  Move to transmit sounds  Eustachian tube  Connect ear with pharynx  Maintains pressure of air of middle ear to environment  Drain fluid & mucus into throat  Swallowing & yawning open Eustachian tube MIDDLE EAR

 Main component for balance  Bony labyrinth-series of canals  Cochlea  Fluid & hair convert mechanical vibration to neural impulses  Semicircular canal  Endolymph-clear fluid maintains equilibrium in motion  Vestibule  maintain static or resting equilibrium  INNER EAR

 Taste buds  Specialized papillae cells  Chemoreceptors  Sweet  Salty  Sour  Bitter  Umami-meatiness Every person has a unique tongue print. Most people have lost 50% of their taste buds by the time they turn 50. GUSTATORY

 Scents send to brain through olfactory nerve  Septum  Divides into right & left  10,000 times more sensitive than taste  5,000 distinct smells can be detected  mix of 30 primary odors  Primary odors  Floral  Putrid  peppermint  Sense has ability to:  Reduce Stress  Affect Blood pressure  Recall memories  Aid in sense of taste OLFACTORY

Meissner's corpuscles light touch and motion Pacinian corpuscles deep pressure End-bulbs of Krause cold, low-frequency vibrations, two-point discrimination Corpuscles of Ruffini heat, deep pressure, and continuous touch Nociceptors Pain receptors Respond to more than one stimulus SKIN

Sight Ophthalmoscope visual acuity- snellen chart Tonometer - measures pressure of the inner eye Hearing Otoscope Audiometer Impedance testing measure s flexibility of TM Rinne’s test -tuning fork assesses transmission of sound through the ear Weber's test- tuning fork to test for unilateral hearing loss ASSESSMENT

Achromatism AKA color blindness Amblyopia AKA lazy eye poor vision in one eye Results from better vision in the other eye Anacusis Hearing loss from damage to neural tissues DISORDERS

Astigmatism Congenital defect imperfect curvature of the cornea Results in blurred vision Cataract Clouding of the lens Conjunctivitis AKA pink eye bacterial or viral inflammation of the eyelid. DISORDERS

CATARACTS

Deafness Complete hearing loss in one or both ears Inherited complications at birth disease excessive noise ototoxic drugs Diabetic retinopathy damaged blood vessels in the retina caused by uncontrolled DM DISORDERS

COCHLEAR IMPLANT

Diplopia AKA double vision muscle imbalance or paralysis of an extraocular muscle. Epistaxis AKA Nosebleed Disease Trauma Hypertension Leukemia rheumatic fever Glaucoma Increased pressure inside the eye trauma hereditary factors

Hyperopia Farsightedness congenital deformity Macular degeneration Slow or sudden, painless loss of central vision

MACULAR DEGENERATION

Ménière's disease Collection of fluid in the labyrinth leads to: dizziness, ringing in the ear (tinnitus), Pressure Deafness Myopia Nearsightedness congenital deformity in the eye Night blindness Poor vision in dim light

Otitis media Middle ear infection bacterial or viral common in young children Presbyopia Type of farsightedness related to aging Retinal detachment Result of injury uncontrolled diabetes mellitus DISORDERS

OTITIS MEDIA

Rhinitis Inflammation of the lining of the nose causes allergic reaction viral infection Sinusitis chemical irritants Ruptured eardrum infection, an explosion a blow to the head a sharp object inserted into the ear Sinusitis Chronic or acute inflammation of a sinus

Strabismus both eyes do not focus on the same point or direction Stye Bacterial infection of the sebaceous glands of the eyelid