Special Senses

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Special Senses
Ch 17
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The Special Senses

• Taste
• Smell
• Vision
• Hearing
• Balance

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Taste
Taste and smell are involved with specific
receptor cells called chemoreceptors  
  
respond to chemicals in an aqueous solution
food dissolved in saliva
airborne chemicals dissolved in mucous membrane
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The Tongue
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Taste Buds
Filiform papilla
Fungiform papilla
Circumvallate Papilla
Tongue epithelium
Connective tissue
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Taste Buds
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Taste Buds
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Five Basic Tastes
Why are they important?
Umami- savory/meaty
Bitter- alkaloid
Sour- H

• Salty- metallic ions

Sweet- sugar
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Experiment
Dry tongue with a paper towel and place a little
sugar on surface. What do you taste?
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Gustatory pathway
Facial nerve? (afferent) 2/3 anterior portion of
tongue Glossophyngeal posterior 1/3 of
tongue Vagus nerve- few taste buds on epiglottis
an pharynx These afferent fibers synapse in
medulla?thalamus? gustatory cortex in parietal
lobes and fibers to hypothalamus in limbic system
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Taste triggers reflex involved in digestion
causes an increase of saliva in mouth (amylase)
and gastric juice in stomach
acids cause strong salivary reflex
bad tasting food causes gagging or reflexive
vomiting
taste can change over time
taste is 80 smell
Mouth also contains
Thermoreceptors Mechanoreceptors Nociceptors-
sensitive nerve fibers that are aware of painful
stimuli
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Olfaction
Smell not as good as animals however, some
people are wine tasters, perfumers If you smell
a particular odor all day, you wont 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
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Olfaction
Olfactory epithelium
Olfactory tract
Olfactory bulb
Nasal conchae
Route of inhaled air
(a)
Figure 15.21a
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Olfaction
Mitral cell (output cell)
Olfactory tract
Glomeruli
Olfactory bulb
Cribriform plate of ethmoid bone
Filaments of olfactory nerve
Lamina propria connective tissue
Olfactory gland
Axon
Basal cell
Olfactory receptor cell
Olfactory epithelium
Supporting cell
Dendrite
Olfactory cilia
Mucus
Route of inhaled air containing odor molecules
(b)
Figure 15.21a
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Cortical Regions Associated with Olfactory
Information
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Anosmias
loss of sense of smell
Lose sense of smell?lose taste
May be genetic or a cold (mucus), allergy, zinc
deficiency
Uncinate- olfactory hallucinations may be
psychological ex. rotting meat smell
Olfactory auras- prior to epileptic attack
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The Eye
palpabre
cornea
Lacrimal caruncle
lateral commisure
Medial commisure
palpabre
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Pupil
bright light
normal light
dim light
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Lacrimal Apparatus
FLOW OF TEARS Lacrimal gland Lacrimal
ducts Sup. or inf. lacrimal canal Lacrimal
sac Nasolacrimal duct Nasal cavity
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Extrinsic Eye Muscles
Superior oblique
Superior rectus
optic nerve
Medial rectus
Inferior oblique
Lateral rectus
Inferior rectus
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Fibrous Tunic
Fibrous tunic- sclera and cornea (outer most
layer) Composed of dense avascular connective
tissue
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Vascular Tunic

• Vascular tunic- uvea choroid, cilliary body,
  iris, pupil (middle layer)
• Choroid- rich vascular nutritive layer contains
  a dark pigment
• that prevents light scattering within the eye
• Cilliary body- lens is attached contains muscles
  that change the
• lenses shape
• Iris- pigmented ring of muscular tissue composed
  of circular
• and radial muscles
• reflex contraction of circular muscle in bright
  light (small dia of pupil)
• reflex contraction of radial muscle in dim light
  (large dia of pupil)
• Pupil- central hole in iris 

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Sensory Tunic

• Sensory tunic- retina (inner most layer)
• Photoreceptors
• rods (dim light, contains pigment rhodopsin) and
• Cones (color vision, not evenly distributed,
  concentrated in fovea)
• Optic disc- blind spot because its where optic
  nerve leaves the eyeball (no rods or cones)
• Macula lutea- yellow spot, area of high cone
• Fovea centralis- in center of macula lutea,
  contains only cones, area of greatest visual
  acuity

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Eye Interior
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Vitreous Humor

• Vitreous humor- behind lens, gel-like substance
  with fine collagenic fibrils imbedded in as
  viscous ground substance- binds with water
• transmits light
• supports the posterior surface of the lens and
  holds the neural retina firmly against pigmented
  layer
• contributes to intraoccular pressure, helping to
  counter act the pulling force of the extrinsic
  eye muscles

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Aqueous Humor

• Aqueous humor- in front of lens, anterior
  segment, watery fluid
• Supplies cornea and lens with nutrients
• Helps to maintain the shape of the eye
• Produced and renewed every 4 hrs by the cilliary
  body      

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Aqueous Humor
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Lens

• Lens- transparent biconvex structure, flexible
• Attached by suspensory ligaments to ciliary body
• focuses image onto retina
• changes lens thickness to allow light to be
  properly focused onto retina

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Focusing the Image

• Coarse Fixed Focusing
• Cornea Shape
• Accommodation- adjust configuration of
• Lens Shape
• Pupil Size

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Properties of Light
refraction
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Focusing on a Near Object
Accomodation
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Accomodation
Focusing on a Far Object
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Refraction Abnormalities

• Emmetropia- normal 2020
• Hyperopia- farsighted
• Myopia-near sighted
• Presbyopia- mature eyes
• Astigmatism

20 ft20 ft
You see
Normal vision
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Snellan Eye Chart
What condition does this person have?
What condition does this person have?
20/10
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Vision Corrective Lenses
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Vision Corrective Lenses
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Astigmatism
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Astigmatism
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Cataract

Clouding of lens (hardening or thickening
causes diabetes mellitus, smoking, UV damage
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Glaucoma
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Red-Green Color Blind Test
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The Retina
blind spot
macula
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Optic Nerve
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light
Retina
Ganglion Amacrine Bipolar neuron Horizontal
cells
Choroid Schlera
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Retina
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Retina
Rod cell membrane
photoreceptors
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Formation breakdown of rhodopsin
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Operation of Rod Photoreceptors
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Primary Visual Pathway
Binocular vision
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Primary Visual Pathway
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Illusions
Geometrical illusions
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Illusions
Successive contrast afterimages ...
fixate the black dot in the center for 60 seconds
... and then look at a the black dot in the
right panel !
                                            what
do you see?
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(No Transcript)
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Auditory System
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Outer Ear
Outer ear- pinna (auricle), lobule, external
auditory canal elastic cartilage External
auditory canal has ceruminous glands- wax
secreting glands- protects delicate lining of
meatus and helps prevent microorganisms from
entering the ear Tympanic membrane- membrane
that vibrates in response to sound waves
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Outer Middle Ear
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Middle Ear
Middle ear- Includes 3 small bones (ossicles)-
hammer (mallus), anvil (incus), stirup (stapes)
Pharyngeotympanic auditory tube (Eustachian
tube)- equalizes pressure connects middle ear to
pharynx. Oval window- found on cochlea stirrup
presses against cochlea Round window- pressure
window on cochlea Otis media- inflammation of the
middle ear due to bacteria or allergies, common
in children whose auditory tubes are short and
horizontal
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Middle Ear
malleus
stapes
incus
oval window
round window
external auditory canal
tympanic membrane
Auditory tube
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(No Transcript)
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Inner Ear
Inner ear- bony labyrinth filled with perilymph
fluid (similar to CFS) and membranous labyrinth
filled with endolymph fluid (similar to K rich
intracellular fluid) these fluids conduct sound
vibrations   Bony labyrinth (includes vestibule,
semicircular canal, and cochlea) Vestibule-
posterior to cochlea and anterior to the
semicircular canals Perilymph fluid suspends 2
membranous sacs utricle and sacule-- they house
equilibrium receptors called maculae that respond
to the pull of gravity
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Inner Ear
Semicircular canal- contains endolymph fluid
anterior, posterior, and lateral canal contains
equilibrium receptors (ampulla) Cochlea- filled
with perilymph fluid Organ of Corti- rests a top
basilar membrane has long row of hair cells
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Inner Ear
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Inner Ear
Biology 100 Human Biology
vestibulochoclear nerve
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The Cochlea
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The Cochlea
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The Organ of Corti
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Properties of Sound

• Properties of sound
• Sound travels at 331 m/sec
• It's a pressure disturbance originating from the
  vibration
• Frequency- cycles/sec (hertz) Reflects sound
  intensity
• Human hearing- 20 to 20,000 htz
• Pitch- different frequency's high vs low pure
  tone is a single frequency
•   Quality- sound mixture with several
  frequencies
•   Intensity- corresponds to amplitude of height
  loudness measured in decibels

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Transmission of Sound
Transmission of sound Airborne sound?external
auditory canal?tympanic membrane?hammer, anvil,
stirrup?oval window?vestubularcochlear
nerve?cochlear nuclei in medulla? superior
olive?up the lateral leminiscus?inferior
colliculus?primary auditory cortex in the
temporal lobe
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Auditory Pathway
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Transmission of sound waves
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Transmission of sound waves
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Transmission of sound waves
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Transmission of sound waves
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Transmission of sound waves
Basilar membrane
High-frequency sounds displace the basilar
membrane near the base.
Fibers of basilar membrane
Medium-frequency sounds displace the basilar
membrane near the middle.
Base (short, stiff fibers)
Apex (long, floppy fibers)

Low-frequency sounds displace the basilar
membrane near the apex.
Frequency (Hz)
(b) Different sound frequencies cross the
basilar membrane at different locations.
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Static Balance utricle and sacule
Static vs Dynamic Equilibrium
Dynamic Balance- semicircular canals
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Semicircular Canal
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Crista of Ampulla
(semicircular canal)
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(semicircular canal)
Crista of Ampulla
Endolymph fluid
Vestibular nerve fibers
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Structure of Macula
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Static Equilibrium
The effect of gravitational pull on the macula
receptor cell in the utricle
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Static Equilibrium
The effect of gravitational pull on the macula
receptor cell in the utricle
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Deafness

• Hearing loss- due to disease (ex. meningitus),
  damage, or age related
• Conduction deafness- prevention or blocking
  sounds from entering inner ear.
• Ex. ear wax, ruptured ear drum, middle ear
  inflammation (otis media), and otosclerosis
  (hardening of the ossicles of the ear)
• Sensoneural deafness- damage to the neural
  structures from any point from the cochlear hair
  cells to and including the auditory cortical
  cells
• Partial or complete deafness, or gradual loss
  over time

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Deafness

• Tinnitus- ringing or clicking sound in the
  absence of auditory stimuli 1st symptom of
  cochlear nerve degeneration
• may result from inflammation of the inner or
  middle ear
• side effect from medicine such as aspirin
• Symptoms- vertigo, nausea, hearing loss
• Meniere's Syndrome- labyrinth disorder effects
  both semicircular canals and cochlea

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IDENTIFY
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INQUIRY

1. What type of stimulus triggers a response in
   nociceptors?
2. Two senses that detect chemical concentrations
   are____.
3. A person with defective otolith sensory receptors
   may have difficulty ______.
4. Which eye muscle moves the eye to look medially?
5. Name the three bones in the middle ear.
6. What is the blind spot in the eye called?
7. Where are the highest concentration of cones
   located?

Hearing Animation http//health.howstuffworks.com
/adam-200010.htm http//www.youtube.com/watch?vdy
enMluFaUw