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Special Senses: Special Senses: Hearing, Taste, Hearing, Taste,
SmellSmellPeripheral Nervous SystemPeripheral Nervous System
Chapter 8Chapter 8
The SensesThe 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 The Ear: Hearing and BalanceBalance
Two functions: Hearing and Two functions: Hearing and BalanceBalance Hearing: Sound vibrationsHearing: Sound vibrations Equilibrium: Gross movementsEquilibrium: Gross movements
MechanoreceptorsMechanoreceptors: respond to : respond to physical forcesphysical forces
Both respond to different stimuli and Both respond to different stimuli and activated separatelyactivated separately
Anatomy of EarAnatomy of Ear
HEARING ONLY
HEARING &
BALANCE
Anatomy of EarAnatomy of Ear
Divided into 3 regions: Divided into 3 regions: External, Middle, InternalExternal, Middle, Internal
External EarExternal Ear Auricle (pinna) and Auditory Auricle (pinna) and Auditory
CanalCanal Ceruminous Glands in canal Ceruminous Glands in canal
secrete earwaxsecrete earwax Tympanic membrane - eardrumTympanic membrane - eardrum
Why do we need earwax???
Earwax protects delicate lining of meatus (auditory canal) and helps prevent microorganisms from entering the ear
Anatomy of EarAnatomy of Ear
Middle EarMiddle Ear Tympanic Cavity – air filled, Tympanic Cavity – air filled,
mucosa-linedmucosa-lined Eustachian Tube – connects to Eustachian Tube – connects to
throatthroat Auditory Auditory ossiclesossicles (tiny bones) (tiny bones)
– hammer, anvil, stirrup– hammer, anvil, stirrup Eustacian tubePressure build upSwallowingyawning“VALSALVA”
THROAT
Otitis mediaOtitis media
Middle ear Middle ear inflammationinflammation
Common with sore Common with sore throat in childrenthroat in children
Enlarge, inflamed Enlarge, inflamed eardrumeardrum
Pus, fluid build up Pus, fluid build up requires incision requires incision and tubes to relieve and tubes to relieve pressure and drainpressure and drain
http://www.petearclinic.com/images_video.htm
http://apps.uwhealth.org/health/hie/2/19596.htm
Anatomy of EarAnatomy of Ear INNER EARINNER EAR
This is a cavityThis is a cavity Bony labyrinth – Bony labyrinth –
bony chamber bony chamber divided into 3 divided into 3 regionsregions CochleaCochlea VestibuleVestibule Semicircular CanalsSemicircular Canals
Two fluids:Two fluids: EndolymphEndolymph PerilymphPerilymph
Labyrinth: an intricate, sometimes confusing, arrangement or pattern
Figure 8.15
HearingHearing
Within Cochlear duct, membranous labyrinth is Spiral Organ of Corti – hearing receptors or “hair cells”
Sound waves > eardrum > ossicles > oval window > set fluid in motion > vibrations stimulate “hair
cells” > cochlear nerve transmits impulse to midbrain > auditory cortex
of temporal lobe
How the ear works…How the ear works…
http://www.youtube.com/watch?http://www.youtube.com/watch?v=dCyz8-eAs1Iv=dCyz8-eAs1I
What is a cochlear implant?What is a cochlear implant?
https://www.youtube.com/watch?https://www.youtube.com/watch?v=6FhgYcfZZY8v=6FhgYcfZZY8
Cochlear implantsCochlear implants
https://www.youtube.com/watch?https://www.youtube.com/watch?v=6FhgYcfZZY8v=6FhgYcfZZY8
Hearing LossHearing LossThe following factors contribute to age-The following factors contribute to age-related hearing loss:related hearing loss:
Family history (tends to run in families)Family history (tends to run in families) Repeated exposure to loud noisesRepeated exposure to loud noises Smoking (smokers are more likely to have such Smoking (smokers are more likely to have such hearing hearing loss than nonsmokers)loss than nonsmokers)
Certain medical conditions and medications Certain medical conditions and medications also contribute to age-related hearing loss. also contribute to age-related hearing loss. About half of all people over age 75 have About half of all people over age 75 have some amount of age-related hearing loss.some amount of age-related hearing loss.
Chemical Senses: Taste and Chemical Senses: Taste and SmellSmell
ChemoreceptorChemoreceptor – respond to – respond to chemicals in solutionchemicals in solution OLFACTORY OLFACTORY = smell= smell GUSTATORYGUSTATORY = taste = taste
Five types of receptors for tasteFive types of receptors for taste Olfactory receptors much more Olfactory receptors much more
sensitivesensitive Complement each other, respond to Complement each other, respond to
same stimulisame 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
During old age, 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
How the nose works…How the nose works…
http://www.youtube.com/watch?http://www.youtube.com/watch?v=dIDBG-UPRUIv=dIDBG-UPRUI
Figure 15.21a
Olfactory tract
Olfactory bulb
(a)
Nasalconchae
Route ofinhaled air
Olfactoryepithelium
Olfactory Receptors: Olfactory Receptors: SmellSmell
1000’s of olfactory receptors roof of 1000’s of olfactory receptors roof of nasal cavitynasal cavity
Sniffing intensifies sense of smellSniffing intensifies sense of smell
Olfactory receptor cells have olfactory Olfactory receptor cells have olfactory hairs – long cilia – in mucus layerhairs – long cilia – in mucus layer
Chemicals in mucus layer stimulate hairs Chemicals in mucus layer stimulate hairs -> filaments -> nerve-> filaments -> nerve
Olfactory impressions long lasting – Olfactory impressions long lasting – memories, adaptivememories, adaptive
Figure 8.17
Figure 15.21a
Mitral cell (output cell)
Olfactorygland
Olfactorytract
Olfactoryepithelium
Filaments of olfactory nerve
Cribriform plate of ethmoid bone
Lamina propria connective tissue
Basal cell
Supporting cell
Dendrite
Olfactory cilia
Olfactory bulbGlomeruli
Axon
Olfactory receptor cell
Mucus
Route of inhaled aircontaining odor molecules(b)
Pathway of smellPathway of smellNostril > nasal cavity > olfactory receptors (sensory neurons) in membrane (top of nasal cavity) > through ethmoid (bone) > olfactory neurons in olfactory bulb > brain
Taste Buds and TasteTaste Buds and Taste Most pleasurable Most pleasurable
sensesense Approx. 10,000 taste Approx. 10,000 taste
buds, most on tonguebuds, most on tongue Papillae – Papillae –
projections, taste projections, taste buds found on sidesbuds found on sides Circumvallate papillae Circumvallate papillae
– sides of tongue– sides of tongue Fungiform papillae – Fungiform papillae –
top, more numeroustop, more numerous
Figure 8.18
How the tongue works…How the tongue works…
https://www.youtube.com/watch?https://www.youtube.com/watch?v=KuP-Kj7MHesv=KuP-Kj7MHes
Taste BudsTaste BudsTaste BudsTaste Buds
Circumvallate Papilla
Filiformpapilla
Fungiformpapilla
Connective tissue Tongue epithelium
Taste BudsTaste Buds
Figure 8.18
Gustatory cells – Gustatory cells – respond to respond to chemicalschemicals
Gustatory hairs – Gustatory hairs – microvilli, protrude microvilli, protrude through taste porethrough taste pore
Chewed food mixes with saliva solution slides down to sides of papillae enters taste pore stimulate gustatory hairs stimulate gustatory receptor cells impulse travels by nerves to brain
Five Taste SensationsFive Taste Sensations SWEETSWEET – sugars, – sugars,
saccharine, some a.a., saccharine, some a.a., lead saltslead salts
SOURSOUR -- acids -- acids BITTERBITTER – alkaloids – alkaloids SALTYSALTY – metal ions in – metal ions in
solutionsolution UMAMIUMAMI– a.a. glutamate, – a.a. glutamate,
“beef taste” and MSG“beef taste” and MSG Only slight differences in Only slight differences in
receptor location. receptor location. Most buds respond to 2+ Most buds respond to 2+
stimulistimuli
http://pactlab-dev.spcomm.uiuc.edu/classes/08SP/280blogs/first_weblog3/2008/02/digitizing-your-taste-buds.html
TasteTaste
Homeostatic roleHomeostatic role Tastes for salt or sugar – minerals or Tastes for salt or sugar – minerals or
carbscarbs Sour – Oranges, lemons – Vitamin CSour – Oranges, lemons – Vitamin C Umami – protein intakeUmami – protein intake Bitter – most poisons and spoiled food Bitter – most poisons and spoiled food
bitter, protectivebitter, protective
Factors of TasteFactors of Taste
Temperature, textureTemperature, texture Spicy food excites pain receptors in Spicy food excites pain receptors in
mouthmouth Taste and Smell ComplementaryTaste and Smell Complementary
Eating when you have coldEating when you have cold
Ghost chile pepper from IndiaHeat Exceptionally hot
Scoville rating 330,000–1,000,000
liquid Oleoresin Capsicum
Loss of Taste & SmellLoss of Taste & Smell
Beginning in 60’s ability to taste and Beginning in 60’s ability to taste and smell diminishessmell diminishes Decrease in # of receptorsDecrease in # of receptors
About 50% over 80 cannot smellAbout 50% over 80 cannot smell
Sense of taste is poorSense of taste is poor
Loss of Taste & SmellLoss of Taste & Smell
Various other factors also can contribute to Various other factors also can contribute to loss of taste and smell, however, including: loss of taste and smell, however, including:
Nasal and sinus problems, such as allergies, Nasal and sinus problems, such as allergies, sinusitis or nasal polyps sinusitis or nasal polyps
Certain medications, including beta blockers and Certain medications, including beta blockers and angiotensin-converting enzyme (ACE) inhibitors angiotensin-converting enzyme (ACE) inhibitors
Tooth decay or poor dental hygiene Tooth decay or poor dental hygiene Cigarette smoking Cigarette smoking Head or facial injury Head or facial injury Alzheimer's disease Alzheimer's disease Parkinson's disease Parkinson's disease
Impact of LOSSImpact of LOSS
Quality of life, often leading to Quality of life, often leading to decreased appetite and poor nutritiondecreased appetite and poor nutrition
Contributes to depressionContributes to depression
Might tempt you to use excess salt or Might tempt you to use excess salt or sugar on your food to enhance the sugar on your food to enhance the taste — which could be a problem if taste — which could be a problem if you have you have high blood pressure high blood pressure or or diabetesdiabetes
Homeostatic ImbalancesHomeostatic Imbalancesof the EAR & NOSEof the EAR & NOSE
Disorder Cause Effect
Otitis media (292)
Skip 3-4 lines
Conduction deafness (297)
Sensorineural deafness (297)
Anosmias (300)