Chapter 8

Special Senses

Chemical Senses• Taste Reception• Taste Buds– Repair in 7-10 days have 10,000– gustatory cells• respond to chemical dissolved in saliva

– papillae• peglike projections

• Primary Taste Sensations– sweet- tip of tongue– sour- sides of tongue– salty- tip of tongue– bitter - base of tongue

Chemical Senses

– Gustatory pathways• facial nerve (VII)• glossopharyngeal (IX)• vagus nerve (X)

– saliva– taste adaptations - 1-5 minutes– tactile: texture, temperature and

irritation (pain)– olfaction plays a part in taste

perception 80%

Chemical Senses

• Olfaction - smell closely tied to emotion– olfactory cells - neurons– olfactory nerve– olfactory hairs– olfactory cells secrete mucus–mucus is constantly replaced– chemoreceptors which detect: 30 - 1000

chemicals

Chemical Senses• Primary Odors– seven• camphoraceous - alcohol ketones• musky• floral• peppermint like• etheral - ethers• pungent - stinging• putrid - rotten

• Smells associated w/ danger– sympathetic nervous

Changes

• Ansomias– loss of smell– age, cold, allergies, smoking, head

injuries– low levels of Zinc

• Sensitivity & Adaptation– adapt to unchanging stimulus

• Pain Receptors– irritants, harmful

The Eye & Vision• Accessory Structures– orbital cavities• location of the eyes• fat & bone

– eyebrows• protect the eyes• shade them• prevent infiltration of perspiration• prevent objects contacting them from above

The Eye & Vision• Accessory Structures– eyelids & eyelashes• protection• lubricate w/ glands (oily secretion)

– conjunctiva• membranes edge of cornea to eyelid• conjunctivitis is pink eye

– lacrimal apparatus - tears• dilute salt solution• antibodies• lysozyme - enzyme kills bacteria

– extrinsic muscles move eyeball

Eye Structure• Fibrous tunic

– anterior portion• cornea - transparent• nerves, no blood vessels

– posterior portion• sclera - outermost protects• thick, white connective tissue

• Vascular tunic (uvea)– choroid

• pigments that absorb light (middle layer) dark purple– ciliary body

• muscles move lens– iris

• pigmented smooth muscles change size of pupil– pupil - opening

Eye Structure• Retina– innermost layer– transparent layer• absorbs light & stores vitamin A

– nervous layer• photoreceptors

– rods - shades of gray– cones - color, red, blue, green– color blindness

– blind spot - optic disc where optic nerve enters

– fovea centralis - lateral to blind spot, only cones greatest visual cavity

Eye Structure• Internal Chambers– Anterior-aqueous humor• corneal shape & nutrition

– canal of Schlemm- drains aqueous humor– glaucoma• increased aqueous humor increase pressure

• Lens– flexible, biconvex, crystal like– held by ligaments– Cataract- clouding of lens

• posterior chamberVitreous humor - gel, eyeball shape

Physiology of Vision• Light Energy– electromagnetic spectrum- wavelengths

• color: cones• Dark and light : rods

• Focusing Processes– refraction

• bending of light

–myopia• nearsighted, eyeball too long, cornea curved

– hypertrophy• farsighted, flat lens, eyeball too short

– astigmatism• unequal curvatures in lens or cornea• blurry vision

Physiology of Vision

• Focusing of Processes– lens accommodation• focus close or far

– pupil constriction• for close vision• for bright light

– eye convergence• close objects

Physiology of Vision

• Photoreception– visual pigments• light absorption• choroid coat - deep purple

– excitation of rods• shades of gray

– excitation of cones• all cones ---> white color

Physiology of Vision• Light and Dark Reception– into light - faster– into dark - slower 20-30 minutes– night blindness• rods function decreased, Vitamin A

deficiency

• Visual Pathways– optic nerve– occipital lobe– cerebrum

• Binocular Vision – eyes anterior– depth perception 3 dimensional vision

The Ear

• Structure– outer ear• auricle• capture sounds shell shaped• external auditory canal• ceruminous glands - make ear wax• tympanic membrane - eardrum

The Ear

• Structure–middle ear• infections otitis media• air filled cavity• bones

– ossicles transmit vibrations– hammer ---> anvil ---> stirrup

• oval window• eustachian tube to throat “auditory”

The Ear• Structure– inner ear

• labyrinth– maze of bony chambers into temporal filled w/ fluid– vestibule– pull of gravity– sacs

• semicircular canal– equilibrium

• cochlea– spiral shaped– organ of corti - receptors– for hearing - hairs

Physiology of the Ear• Sound waves

– frequency– amplitude

• Outer and middle ear– reception– increase & decrease sound

• Cochlea– organ of hearing

• sound ---> cochlear nerve ---> temporal lobe

• Pitch transmission– frequency specific hairs

• Loudness transmission– amplitude– more hairs stimulated

Homeostasis Imbalances• Deafness– conduction deafness - hearing aid– sensorineural deafness• loud noise• damage organ of corti

• Tinnitus– ringing in ears, clicking

• Meniere’s Syndrome– arteriosclerosis– cranial nerve fluid pressure & “howling”

• Motion Sickness– sensory input