Anatomy of Ear
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Transcript Anatomy of Ear
Special Senses:
Hearing, Taste, Smell
Peripheral Nervous System
Chapter 15
The Senses
General senses of touch (tactile)
Temperature - thermoreceptors (heat)
Pressure - mechanoreceptors (movement)
Pain - mechanoreceptors
Special senses
Smell - chemoreceptors (chemicals)
Taste - chemoreceptors
Sight - photoreceptors (light)
Hearing - mechanoreceptors
Equilibrium - (balance) mechanoreceptors
The Ear: Hearing and Balance
Two functions: Hearing and Balance
Hearing:
Sound vibrations
Equilibrium: Gross movements
Mechanoreceptors:
respond to physical forces
Both respond to different stimuli and
activated separately
Anatomy of Ear
HEARING
ONLY
HEARING
&
BALANCE
Anatomy of Ear
Why do we need earwax???
Divided into 3 regions:
External,
Middle,
Internal
Earwax
protects
delicate
lining of meatus
(auditory canal) and helps prevent
External Ear
microorganisms from entering the ear
Auricle
(pinna) and Auditory Canal
Ceruminous Glands in canal secrete earwax
Tympanic membrane - eardrum
Anatomy of Ear
Middle Ear
Tympanic
Cavity – air filled, mucosa-
lined
Eustachian Tube – connects to throat
Auditory ossicles (tiny bones) –
hammer, anvil, stirrup
Pressure build up
Swallowing
yawning
“VALSALVA”
Eustacian tube
THROAT
Otitis media
http://www.petearclinic.com/images_video.htm
http://apps.uwhealth.org/health/hie/2/19596.htm
Middle ear inflammation
Common with sore
throat in children
Enlarge, inflamed
eardrum
Pus, fluid build up
requires incision and
tubes to relieve pressure
and drain
Anatomy of Ear
INNER EAR
This is a cavity
Bony labyrinth – bony
chamber divided into
3 regions
Cochlea
Vestibule
Semicircular Canals
Two fluids:
Endolymph
Perilymph
Labyrinth:
an intricate, sometimes
confusing, arrangement or
pattern
Hearing
Sound waves > eardrum > ossicles >
oval window > set fluid in motion >
vibrations stimulate “hair
cells”
> cochlear
Within
Cochlear
duct,
membranous
labyrinth
nerve transmits impulse
to midbrain
> is
Spiral
Organ of
Corti –
auditory cortex of
temporal
lobe
hearing receptors or “hair
cells”
Figure 8.15
How the ear works…
http://www.youtube.com/watch?v=dCyz8eAs1I
Chemical Senses: Taste and Smell
Chemoreceptor – respond to chemicals in
solution
OLFACTORY = smell
GUSTATORY = taste
Five types of receptors for taste
Olfactory receptors much more sensitive
Complement each other, respond to same
stimuli
Smell not as good as animals; however, some people
are wine tasters, perfumers
If you smell a particular odor all day, you won’t
recognize its presence, you become accustomed, ex.
garbage men
Old people lose sense of smell- lots of perfume
Humans can distinguish 10,000 or so chemicals
What we really smell is pain: ex. chili, ammonia,
menthol (cold)
Specific chemicals cause specific patterns of neurons
to fire
Olfactory
epithelium
Olfactory tract
Olfactory bulb
Nasal
conchae
(a)
Route of
inhaled air
Figure 15.21a
Olfactory Receptors: Smell
1000’s of olfactory receptors roof of nasal cavity
Sniffing intensifies sense of smell
Olfactory receptor cells have olfactory hairs –
long cilia – in mucus layer
Chemicals in mucus layer stimulate hairs ->
filaments -> nerve
Olfactory impressions long lasting – memories,
adaptive
Figure
8.17
Olfactory
tract
Mitral cell (output cell)
Glomeruli
Olfactory bulb
Cribriform plate of ethmoid bone
Filaments of olfactory nerve
Olfactory
gland
Lamina propria connective tissue
Axon
Basal cell
Olfactory receptor cell
Olfactory
epithelium
Supporting cell
Mucus
(b)
Dendrite
Olfactory cilia
Route of inhaled air
containing odor molecules
Figure 15.21a
Pathway of smell
Nostril > nasal cavity > olfactory
receptors (sensory neurons) in membrane
(top of nasal cavity) > through ethmoid
(bone) > olfactory neurons in
olfactory bulb > brain
http://www.youtube.com/watch?v=dIDBGUPRUI
Taste Buds and Taste
Most pleasurable sense
Approx. 10,000 taste
buds, most on tongue
Papillae – projections,
taste buds found on
sides
Circumvallate papillae –
sides of tongue
Fungiform papillae –
top, more numerous
Figure 8.18
Taste Buds
Filiform
papilla
Fungiform
papilla
Circumvallate Papilla
Connective tissue
Tongue epithelium
Taste Buds
Gustatory cells – respond
to chemicals
Gustatory
Chewed food mixes with
saliva hairs
> –
microvilli,
protrude >
solution slides down to sides
of papillae
through taste
pore
enters taste pore > stimulate
gustatory
hairs > stimulate gustatory receptor cells >
impulse travels by nerves to brain
Figure 8.18
Five Taste Sensations
SWEET – sugars, saccharine,
some a.a., lead salts
SOUR -- acids
BITTER – alkaloids
SALTY – metal ions in
solution
UMAMI– a.a. glutamate,
“beef taste” and MSG
Only slight differences in
receptor location.
Most buds respond to 2+
stimuli
http://pactlab-dev.spcomm.uiuc.edu/classes/08SP/280blogs/first_weblog3/2008/02/digitizing-your-taste-buds.html
Taste
Homeostatic role
Tastes for salt or sugar – minerals or carbs
Sour – Oranges, lemons – Vitamin C
Umami – protein intake
Bitter – most poisons and spoiled food bitter,
protective
Factors of Taste
Temperature, texture
Spicy food excites pain receptors in mouth
Taste and Smell Complementary
Eating when you have cold
Loss of Chemical Senses
Beginning in 40’s ability to taste and smell
diminishes
Decrease in # of receptors
About 50% over 80 cannot smell
Sense of taste is poor
The End