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
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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
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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
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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
• Fibrous tunic
Eye Structure
– 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 chamber
Vitreous 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
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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
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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