Questions to discuss:
Describe the sensation when you initially
put your fingers in the water.
After two minutes describe how the
sensation has changed.
Once you submerse your fingers in the third
cup of water, discuss any and all sensations.
Determine the neurological pathway for the
detection and perception of temperature.
10 - 1
CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hole’s Essentials of Human
Anatomy & Physiology
David Shier
Jackie Butler
Ricki Lewis
Created by Lu Anne Clark
Professor of Science, Lansing Community College
Chapter 10
Lecture Outlines*
*See PowerPoint image slides for all figures and tables
pre-inserted into PowerPoint without notes”.
10 - 2
Breakdown Video: How does the
video demonstrate the following?
Levels of Organization
Interconnection of Systems
Reasons for disruption of homeostasis
10 - 3

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Chapter 10
Somatic and
Special Senses
10 - 4

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Introduction
A. Sensory receptors detect changes in the
environment and stimulate neurons to
send nerve impulses to the brain.
B. A sensation is formed based on the
sensory input.
10 - 5
10 - 6

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Receptors and Sensations
A. Each receptor is more sensitive to a
specific kind of environmental change
but is less sensitive to others.
10 - 7
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B. Types of Receptors
Five general types of receptors are
recognized.
1.
Receptors sensitive to changes
in chemical concentration are
called chemoreceptors.
2.
Pain receptors detect tissue
damage.
10 - 8
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3.
4.
5.
10 - 9
Thermoreceptors respond
to temperature differences.
Mechanoreceptors respond
to changes in pressure or
movement.
Photoreceptors in the eyes
respond to light energy.
10 - 10
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C. Sensations
1.
Sensations are feelings that occur
when the brain interprets sensory
impulses.
2.
At the same time the sensation is
being formed, the brain uses
projection to send the sensation
back to its point of origin so the
person can pinpoint the area of
stimulation.
10 - 11
10 - 12
10 - 13
10 - 14
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CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
D. Sensory Adaptation
1.
During sensory adaptation,
sensory impulses are sent at
decreasing rates until receptors fail
to send impulses unless there is a
change in strength of the stimulus.
This is one of the focus areas of
the lab
10 - 15
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CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Somatic Senses
A. Receptors associated with the skin,
muscles, joints, and viscera make up the
somatic senses.
Touch, temperature, pain and position (TTPP)
(Q: What is viscera?)
10 - 16
Viscera = internal organs of thoracic
and abdominal cavities
10 - 17
Somatic Receptors
10 - 18
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CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
B. Touch and Pressure Senses
1.
Three types of receptors detect
touch and pressure.
2.
Free ends of sensory nerve fibers in
the epithelial tissues are associated
with touch and pressure.
10 - 19

10 - 20
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
3.
4.
10 - 21
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Meissner's corpuscles are
flattened connective tissue sheaths
surrounding two or more nerve
fibers and are abundant in hairless
areas that are very sensitive to
touch, like the lips.
Pacinian corpuscles are large
structures of connective tissue and
cells that resemble an onion. They
function to detect deep pressure.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
C. Temperature Senses
1.
Temperature receptors include two
groups of free nerve endings: heat
receptors and cold receptors which
both work best within a range of
temperatures.
10 - 22
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a.
b.
10 - 23
Both heat and cold receptors
adapt quickly.
Temperatures near 45o C
stimulate pain receptors;
temperatures below 10o C also
stimulate pain receptors and
produce a freezing sensation.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
D. Sense of Pain
1.
Pain receptors consist of free nerve
endings that are stimulated when
tissues are damaged, and adapt
little, if at all.
2.
Many stimuli affect pain receptors
such as chemicals and oxygen
deprivation.
10 - 24

3.
10 - 25
CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Visceral pain receptors are the only
receptors in the viscera that
produce sensations.
a.
Referred pain occurs because
of the common nerve
pathways leading from skin
and internal organs.
Pain felt in one area of the body does not always represent where the
problem is, because the pain may be referred there from another
area. For example, pain produced by a heart attack may feel as if
it is coming from the arm because sensory information from the
heart and the arm converge on the same nerve cells in the spinal
cord.
10 - 26

4.
10 - 27
CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pain Nerve Fibers
a.
Fibers conducting pain
impulses away from their
source are either acute pain
fibers or chronic pain fibers.
b.
Acute pain fibers are thin,
myelinated fibers that carry
impulses rapidly and cease
when the stimulus stops.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
c.
10 - 28
Chronic pain fibers are thin,
unmyelinated fibers that
conduct impulses slowly and
continue sending impulses
after the stimulus stops.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
d.
e.
10 - 29
Pain impulses are processed in
the gray matter of the dorsal
horn of the spinal cord.
Pain impulses are conducted
to the thalamus,
hypothalamus, and cerebral
cortex.

5.
10 - 30
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Regulation of Pain Impulses
a.
A person becomes aware of
pain when impulses reach the
thalamus, but the cerebral
cortex judges the intensity
and location of the pain.
Pathway
of Pain
10 - 31
Special Senses
32
I. Types of Receptors
A.
Chemoreceptors - are stimulated by changes
in the chemical concentration of substances.
B. Pain receptors - are stimulated by tissue
damage.
C. Thermoreceptors - stimulated by changes in
temperature.
D. Mechanoreceptors- are stimulated by changes
in movement or pressure.
E. Photoreceptors- are stimulated by light
energy.
10 - 33
Olfactory
System
34
I. General Information
A. Both taste and smell are chemoreceptors,
which means that chemicals must dissolve in
liquids to stimulate the receptors.
B. Olfaction (smell) and gustation (taste) senses
are tied into one another.
C. Sensory adaptation means that as a receptor
adapts, the impulses leave them at a
decreasing rate, until it stops sending signals.
D. Olfactory adaptation is rapid (doesn’t require
many molecules of odorants), but memory is
long term.
10 - 35
II. Olfactory Anatomy
A. Epithelium
1. One square inch of
membrane holds 10100 million receptors
2. Covers superior nasal
cavity and cribriform
plate.
10 - 36
B. Olfactory Membrane
1. Olfactory receptors
 bipolar neurons w/cilia
2. Supporting cells
3. Basal cells = stem cells
 replace receptors
monthly
4. Olfactory glands
 produces mucus
10 - 37
III. Olfaction: Sense of Smell
A. Odorants dissolve in
mucus to bind to
receptors.
B. Nerve impulses are sent
through the bony
cribiform plate to the
olfactory bulb of the
brain.
C. If each odor stimulates a
distinct set of receptor
subtypes, it will create a
variety of odors.
10 - 38
Odor Thresholds
1. Strong odors also stimulates the
trigeminal nerve which results in
stimulation of nasal mucus cells as
well as tear cells.
2. Partial or complete loss of smell is
called anosmia.
10 - 39
Gustatory Sensation: Taste
1. Taste requires dissolving of
substances
2. Four classes of stimuli--sour,
bitter, sweet, and salty
3. 10,000 taste buds found on
tongue, soft palate & larynx
4. Found on sides of
circumvallate & fungiform
papillae
5. 3 cell types: supporting,
receptor & basal cells
10 - 40
Anatomy of Taste Buds
1. An oval body
consisting of 50
receptor cells
surrounded by
supporting cells
2. A single gustatory hair
projects upward
through the taste pore
3. Basal cells develop
into new receptor cells
every 10 days.
10 - 41
Physiology of Taste
1. Complete adaptation in 1 to 5 minutes
2. Thresholds for tastes vary among the 4
primary tastes
a) most sensitive to bitter (poisons)
b) least sensitive to salty and sweet
3. Mechanism
a) dissolved substance contacts gustatory hairs
b) receptor potential results in neurotransmitter
release
10 - 42 c) nerve impulse formed in 1st-order neuron
Taste Nerve Pathway: add to notes
Taste receptor in tongue
Sensory neuron to:
Facial, glossopharyngeal and vagus cranial
nerves
To medulla oblongata
To thalamus
To parietal lobe of cerebrum (gustatory
cortex)
10 - 43
Special Sense: VISION
Accessory Structures of Eye
Fibrous Tunic of Eyeball
Vascular Tunic of Eyeball
Nervous Tunic of Eyeball
Physiology of Vision – images
Physiology of Vision - color
10 - 44
Accessory Structures of Eye
1. Eyelids
a) protect & lubricate
2. Tarsal glands
a) oily secretions
keep lids from
sticking together
3. Conjunctiva
a) stops at corneal
edge
b) dilated BV-bloodshot
10 - 45
Eyelashes & Eyebrows
Eyeball = 1
inch diameter
5/6 of Eyeball
inside orbit &
protected
1. Eyelashes & eyebrows help protect from foreign objects,
perspiration & sunlight
2. Sebaceous glands are found at base of eyelashes (sty)
3. 10Palpebral
fissure is gap between the eyelids
- 46
Lacrimal Apparatus (pg 278;
fig. 10-16)
1. About 1 ml of tears produced per day. Spread over eye by
blinking.
Contains bactericidal enzyme called lysozyme.
10 - 47
Tunics (Layers) of Eyeball
1. Fibrous Tunic
(outer layer)
2. Vascular Tunic
(middle layer)
3. Nervous Tunic
(inner layer)
10 - 48
Fibrous Tunic -Cornea
1. Transparent
2. Helps focus light(refraction)
a) astigmatism
3. Transplants
a) common & successful
b) no blood vessels so no antibodies
to cause rejection
4. Nourished by tears & aqueous
humor
10 - 49
Fibrous Tunic - Sclera
1. Dense irregular
connective tissue
layer
2. Provides shape &
support
3. Pierced by Optic
Nerve (posterior)
10 - 50
Vascular Tunic -Choroid & Ciliary Body
1.
Choroid
a) melanocytes & blood vessels
b) provides nutrients to retina
c) black pigment in melanocytes
absorb scattered light
2. Ciliary body
a) ciliary processes
1. folds on ciliary body
secrete aqueous humor
b) ciliary muscle
1. smooth muscle that alters
shape of lens
10 - 51
Vascular Tunic- Iris & Pupil
1. Colored portion of eye
2. Shape of flat donut
suspended between
cornea & lens
3. Hole in center is pupil
4. Function is to regulate
amount of light entering
eye
5. Autonomic reflexes
a) circular muscle fibers contract in bright light to shrink pupil
b) radial muscle fibers contract in dim light to enlarge pupil
10 - 52
Muscles of the Iris
1. Constrictor pupillae (circular) are innervated by
parasympathetic fibers while Dilator pupillae
(radial) are innervated by sympathetic fibers.
2. Response varies with different levels of light
10 - 53
Vascular Tunic -Lens
1. Avascular
2. Crystallin proteins
arranged like layers in
onion
3. Clear capsule &
perfectly transparent
4. Lens held in place by
suspensory ligaments
5. Focuses light on fovea
10 - 54
Suspensory ligament
1. Suspensory ligaments attach lens to ciliary process
10 -2.
55 Ciliary muscle controls tension on ligaments & lens
Nervous Tunic - Retina
1. Optic disc
a) optic nerve exiting
back of eyeball
2. Central retina BV
a) fan out to supply
nourishment to retina
b) visible for inspection
• hypertension &
diabetes
3. Detached retina
a) trauma (boxing)
View with Ophthalmoscope
10 - 56
•
•
fluid between layers
distortion or blindness
Layers of Retina
1. Pigmented epithelium
a) nonvisual portion
b) absorbs stray light & helps
keep image clear
2. Three layers of neurons
a) photoreceptor layer
b) bipolar neuron layer
c) ganglion neuron layer
10 - 57
Photoreceptors
1. Rods
a) shades of gray in dim light
b) 120 million rod cells
c) discriminates shapes &
movements
d) distributed along periphery
2. Cones
a) sharp, color vision
b) 6 million
c) Centrally located e.g. fovea
10 - 58
Major Processes of Image
Formation
1. Refraction of light
a) by cornea & lens
b) light rays must fall upon the retina
2. Accommodation of the lens
a) changing shape of lens so that light is focused
3. Constriction of the pupil
a) less light enters the eye
10 - 59
Definition of Refraction
1. Bending of light as it passes from one substance (air)
into a 2nd substance with a different density(cornea)
2. In the eye, light is refracted by the anterior & posterior
surfaces of the cornea and the lens
10 - 60
Refraction by the
Cornea & Lens
1.
2.
3.
4.
5.
Image focused on retina is inverted & reversed from left
to right
Brain learns to work with that information
75% of Refraction is done by
cornea -- rest is done by the lens
Light rays from > 20’ are nearly parallel and only need
to be bent enough to focus on retina
Light rays from < 6’ are more divergent & need more
refraction

10 - 61
extra process needed to get additional bending of light is
called accommodation
Accommodation & the Lens
1.
2.
3.
Convex lens refract light rays
towards each other
Lens of eye is convex on both
surfaces
View a distant object
a)
4.
lens is nearly flat by pulling of
suspensory ligaments
View a close object
a)
b)
c)
10 - 62
ciliary muscle is contracted &
decreases the pull of the
suspensory ligaments on the lens
elastic lens thickens as the
tension is removed from it
increase in curvature of lens is
called accommodation
Correction for Refraction Problems
1. Emmetropic eye (normal)
a) can refract light from 20 ft away
2. Myopia (nearsighted)
a) eyeball is too long from front to
back
b) glasses concave
3. Hypermetropic (farsighted)
a) eyeball is too short
b) glasses convex (coke-bottle)
4. Astigmatism
a) corneal surface wavy
b) parts of image out of focus
10 - 63
nvergence of the Eyes
1. Binocular vision in humans has both eyes
looking at the same object
2. As you look at an object close to your face,
both eyeballs must turn inward.
a) convergence
b) required so that light rays from the object will
strike both retinas at the same relative point
c) extrinsic eye muscles must coordinate this action
10 - 64
10 - 65
Photoreceptors
1. Named for shape of outer segment
2. Transduction of light energy into a
receptor potential in outer segment
3. Photopigment is integral membrane
protein of outer segment membrane
4. Photopigments = opsin (protein) +
retinal (derivative of vitamin A)
a) rods contain rhodopsin
b) cone photopigments contain 3 different
opsin proteins permitting the absorption of 3
different wavelengths (colors) of light
10 - 66
Photopigment Physiology
1. Isomerization
a) light causes cis-retinal to
straighten & become
trans-retinal shape
2. Bleaching
a) enzymes separate the
trans-retinal from the
opsin
b) colorless final products
3. Regeneration
10 - 67
a) in darkness, an enzyme
converts trans-retinal
back to cis-retinal
Regeneration of
Photopigments
1. Pigment epithelium near the photoreceptors
contains large amounts of vitamin A and helps
the regeneration process
2. After complete bleaching, it takes 5 minutes
to regenerate 1/2 of the rhodopsin but only
90 seconds to regenerate the cone
photopigments
3. Full regeneration of bleached rhodopsin takes
30 to 40 minutes
4. Rods contribute little to daylight vision, since
10 - 68
they are bleached as fast as they regenerate.
Photopigments for cones
3 Types of opsin protein (different form than
opsin in rods)
Retinal + opsin = photopigment
Blue photopigment
Red photopigment
Green photopigment
The length of the wavelength stimulates certain
cones (and various combos = various colors)
10 - 69
10 - 70
Color Blindness & Night Blindness
1. Color blindness
a) inability to distinguish between certain colors
b) absence of certain cone photopigments
c) red-green color blind person can not tell red
from green
2. Night blindness (nyctalopia)
a) difficulty seeing in low light
b) inability to make normal amount of rhodopsin
c) possibly due to deficiency of vitamin A
10 - 71
Brain Pathways of Vision
synapse in thalamus
& visual cortex
10 - 72
10 - 73
10 - 74
Anatomy of the Ear Region
10 - 75
10 - 76
External Ear
1. Function = collect sounds
2. Structures
a) auricle or pinna

elastic cartilage covered with skin
b) external auditory canal


curved 1” tube of cartilage & bone leading into temporal bone
ceruminous glands produce cerumen = ear wax
c) tympanic membrane or eardrum

epidermis, collagen & elastic fibers, simple cuboidal epith.
3. Perforated eardrum (hole is present)
1. at time of injury (pain, ringing, hearing loss, dizziness)
2. caused by explosion, scuba diving, or ear infection
10 - 77
Middle Ear Cavity
10 - 78
Middle Ear Cavity
1. Air filled cavity in the temporal
bone
2. Separated from external ear by
eardrum and from internal ear by
oval & round window
3. Three ear ossicles connected by synovial joints
a) malleus attached to eardrum, incus & stapes attached
by foot plate to membrane of oval window
b) stapedius and tensor tympani muscles attach to ossicles
4. Auditory tube leads to nasopharynx
a) helps to equalize pressure on both sides of eardrum
10 - 79
Inner Ear-Bony Labyrinth
Vestibule
canals
ampulla
1. Bony labyrinth = set of tube-like cavities in temporal bone
a) semicircular canals, vestibule & cochlea lined with periosteum & filled
with perilymph
b) surrounds & protects Membranous Labyrinth
10 - 80
Cochlear Anatomy
1. 3 fluid filled channels found within the cochlea
a) scala vestibuli, scala tympani and cochlear duct
2.
Vibration of the stapes upon the oval window sends
10 - 81
vibrations into the fluid of the scala vestibuli
Anatomy of the Organ of Corti
1. Microvilli make contact with tectorial
membrane (gelatinous membrane that
overlaps the spiral organ of Corti)
10 - 82
Physiology of Hearing
1. Auricle collects sound waves
2. Eardrum vibrates
a) slow vibration in response to low-pitched sounds
b) rapid vibration in response to high-pitched sounds
3. Ossicles vibrate since malleus attached to eardrum
4. Stapes pushes on oval window producing fluid
pressure waves in scala vestibuli & tympani
5. Pressure fluctuations inside cochlear duct move the
hair cells against the tectorial membrane
6. Microvilli are bent producing receptor potentials
7. Depolarization of vestibulocochlear cranial nerve
to auditory cortex in temporal lobe
10 - 83
10 - 84
Overview of Physiology of Hearing
10 - 85
Deafness
1. Nerve deafness
a) damage to hair cells from antibiotics, high
pitched sounds, anticancer drugs
 the louder the sound the quicker the hearing
loss
b) fail to notice until difficulty with speech
2. Conduction deafness
a) perforated eardrum
b) otosclerosis
10 - 86
Cochlear Implants
1. If deafness is due to destruction of
hair cells
2. Microphone, microprocessor &
electrodes translate sounds into
electric stimulation of the
vestibulocochlear nerve
3. Provides only a crude representation
of sounds
10 - 87
Physiology of Equilibrium (Balance)
1. Static equilibrium
a) maintain the position of the body (head)
relative to the force of gravity
b) macula receptors within saccule & utricle
2. Dynamic equilibrium
a) maintain body position (head) during
sudden movement of any type--rotation,
deceleration or acceleration
b) crista receptors within ampulla of
semicircular ducts
10 - 88
Vestibular Apparatus
Notice: semicircular ducts with ampulla, utricle & saccule
10 - 89
Otolithic Organs: Saccule & Utricle
macula
1. Thickened regions called macula within the saccule &
utricle of the vestibular apparatus
2. Cell types in the macula region
a) hair cells with stereocilia (microvilli) & one cilia (kinocilium)
b) supporting cells that secrete gelatinous layer
3. Gelatinous otolithic membrane contains calcium carbonate
crystals called otoliths that move when you tip your head
10 - 90
Detection of Position of Head
Movement of stereocilia or kinocilium results in
the release of neurotransmitter onto the
10 - 91
vestibular branches of the vestibulocochler nerve
Crista: Ampulla of Semicircular Ducts
1. Small elevation within each of three semicircular ducts
a) anterior, posterior & horizontal ducts detect different movements
2. Hair cells covered with cupula of gelatinous material
3. When you move, fluid in canal bends cupula stimulating hair
cells that release neurotransmitter
10 - 92
Detection of Rotational Movement
1. When head moves, the attached semicircular ducts and hair
cells move with it
a) endolymph fluid moves and bends the cupula and enclosed hair cells
2. Nerve signals to the brain are generated indicating which
10 - 93
direction the head has been rotated

10 - 94
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
10 - 95
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Auditory Nerve Pathways
1.
Nerve fibers carry impulses to
the auditory cortices of the
temporal lobes where they are
interpreted.
10 - 96
Dynamic balance
Cerebellum plays huge role in maintaining
balance
What other senses would send information
to the cerebellum regarding information for
balance?
10 - 97
THE END
10 - 98
Design Your Test (partially)
Somatic anatomy and physiology
Hearing anatomy and physiology
Sight anatomy and physiology
Smell and taste anatomy and physiology
10 - 99
Structure and Process
Goal: as a group design an interactive
learning center for students to understand
the structures (anatomy) involved in one
of the senses studied
Goal: as a group design an interactive
learning center for students to understand
the process (physiology) involved in one of
the senses studied
10 - 100
Use on exam
If sufficient details are provided by the
center, the exact content will be used on the
test.
If not, then teacher generated content will
be used for the test.
10 - 101
Details for the center
Group will be assigned one of the senses
Materials such as lab book, textbook and
notes should be used.
10 - 102
Details for the center: Anatomy
Use large paper provided to draw structures
involved in the sense. UNLABELED
Provide cards with the names of the
structures that go with the unlabeled
drawing.
Your group decides the necessary content
10 - 103
10 - 104
Details for the center: Physiology
Design a learning activity to help students
to understand the processes involved in the
sense.
Examples:
• pathway flashcards that students can arrange in a
specific order
• Pathway diagram to be arranged
• Flashcards for match game – need to provide key for
student use
10 - 105
10 - 106
Additional information
Provide page numbers for text and lab
manual or state refer to notes to help guide
the students
Provide a key to students – ONLY after
they attempt the learning themselves
10 - 107

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Sense of Hearing
A. The ear has external, middle, and inner
sections and provides the senses of
hearing and equilibrium.
B. Outer (External) Ear
1.
The external ear consists of the
auricle, which collects the sound,
which then travels down the
external auditory meatus.
10 - 108

10 - 109
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
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C. Middle Ear
1. The middle ear begins with the
tympanic membrane, and is an airfilled space (tympanic cavity)
housing the auditory ossicles.
10 - 110

10 - 111
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
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a.
Three auditory ossicles are the
malleus, incus, and stapes.
b.
The tympanic membrane
vibrates the malleus, which
vibrates
the incus, then the stapes.
c.
The stapes vibrates the fluid
inside the oval window of the
inner ear.
2. Auditory ossicles both transmit and
amplify sound waves.
10 - 112
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D. Auditory Tube
1. The auditory, or eustachian,
tube connects the middle ear to the
throat to help maintain equal air
pressure on both sides of the
eardrum.
10 - 113
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E. Inner (Internal) Ear
1.
The inner ear is made up of a
membranous labyrinth inside an
osseous labyrinth.
a.
Between the two labyrinths is
a fluid called perilymph.
b.
Endolymph is inside the
membranous labyrinth.
10 - 114

10 - 115
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
CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2. The cochlea houses the organ of
hearing; while the semicircular canals
function in equilibrium.
3. Within the cochlea, the oval window
leads to the upper compartment, called
the scala vestibuli.
10 - 116
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4. A lower compartment, the scala
tympani, leads to the round window.
5. The cochlear duct lies between these
two compartments and is separated from
the scala vestibuli by the vestibular
membrane, and from the scala tympani
by the basilar membrane.
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6. The organ of Corti, with its receptors
called hair cells, lies on the basilar
membrane.
a.
Hair cells possess hairs that extend
into the endolymph of the cochlear
duct.
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
7.
8.
9.
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Above the hair cells lies the tectorial
membrane, which touches the tips
of the stereocilia.
Vibrations in the fluid of the inner
ear cause the hair cells to bend
resulting in an influx of calcium ions.
This causes the release of a
neurotransmitter from vesicles
which stimulate the ends of nearby
sensory neurons.

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
F.
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Auditory Nerve Pathways
1.
Nerve fibers carry impulses to
the auditory cortices of the
temporal lobes where they are
interpreted.
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Sense of Equilibrium
A.
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The sense of equilibrium consists of
two parts: static and dynamic
equilibrium.
1.
The organs of static
equilibrium help to maintain
the position of the head when
the head and body are still.
2.
The organs of dynamic
equilibrium help to maintain
balance when the head and
body suddenly move and
rotate.

B.
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Static Equilibrium
1.
The organs of static
equilibrium are located within
the bony vestibule of the inner
ear, inside the utricle and
saccule (expansions of the
membranous labyrinth).
2.
A macula, consisting of hair
cells and supporting cells, lies
inside the utricle and
saccule.
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3.
4.
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The hair cells contact
gelatinous material holding
otoliths.
Gravity causes the gelatin and
otoliths to shift, bending hair
cells and generating a nervous
impulse.
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5.
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Impulses travel to the brain
via the vestibular branch of
the vestibulocochlear nerve,
indicating the position of the
head.

C.
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Dynamic Equilibrium
1.
The three semicircular canals
detect motion of the head,
and they aid in balancing the
head and body during sudden
movement.
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2.
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The organs of dynamic
equilibrium are called cristae
ampullaris, and are located in
the ampulla of each
semicircular canal of the inner
ear. They are at right angles
to each other.
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3.
4.
5.
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Hair cells extend into a domeshaped gelatinous cupula.
Rapid turning of the head or
body generates impulses as
the cupula and hair cells bend.
Mechanoreceptors (called
propriopceptors) associated
with the joints, and the
changes detected by the eyes
also help maintain equilibrium.
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Sense of Smell
A. Olfactory Receptors
1.
Olfactory receptors are
chemoreceptors.
2.
The senses of smell and taste
operate together to aid in food
selection.
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B. Olfactory Organs
1.
The olfactory organs contain the
olfactory receptors plus epithelial
supporting cells and are located in
the upper nasal cavity.
2.
The receptor cells are bipolar
neurons with hairlike cilia covering
the dendrites. The cilia project into
the nasal cavity.
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
3.
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To be detected, chemicals that
enter the nasal cavity must first be
dissolved in the watery fluid
surrounding the cilia.
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C. Olfactory Nerve Pathways
1.
When olfactory receptors are
stimulated, their fibers synapse with
neurons in the olfactory lobes lying
on either side of the crista galli.
2.
Sensory impulses are first analyzed
in the olfactory lobes, then travel
along olfactory tracts to the limbic
system, and lastly to the olfactory
cortex within the temporal lobes.
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D. Olfactory Stimulation
1.
Scientists are uncertain of how
olfactory reception operates but
believe that each odor stimulates a
set of specific protein receptors in
cell membranes.
2.
The brain interprets different
receptor combinations as an
olfactory code.
3.
Olfactory receptors adapt quickly
but selectively.
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Sense of Taste
A. Taste buds are the organs of taste and
are located within papillae of the tongue
and are scattered throughout the mouth
and pharynx.
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
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B. Taste Receptors
1.
Taste cells (gustatory cells) are
modified epithelial cells that function
as receptors.
2.
Taste cells contain the taste hairs
that are the portions sensitive to
taste. These hairs protrude from
openings called taste pores.
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
3.
4.
5.
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Chemicals must be dissolved in
water (saliva) in order to be tasted.
The sense of taste is not well
understood but probably involves
specific membrane protein receptors
that bind with specific chemicals in
food.
There are four types of taste cells.

C.
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Taste Sensations
1.
Specific taste receptors are
concentrated in different areas
of the tongue.
a.
Sweet receptors are
plentiful near the tip of
the tongue.
b.
Sour receptors occur
along the lateral edges
of the tongue.
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c.
d.
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Salt receptors are
abundant in the tip and
upper portion of the
tongue.
Bitter receptors are at
the back of the tongue.

2.
3.
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Taste buds may be responsive to at
least 2 taste sensations but one is
likely to dominate.
Taste receptors rapidly undergo
adaptation.

D.
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Taste Nerve Pathways
1.
Taste impulses travel on the
facial, glossopharyngeal, and
vagus nerves to the medulla
oblongata and then to the
gustatory cortex of the
cerebrum.
Click here to play
Effect of Sound Waves
on the Cochlear
Flash Animation
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Sense of Sight
A.
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Accessory organs, namely the
lacrimal apparatus, eyelids, and
extrinsic muscles, aid the eye in its
function.

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
B.
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Visual Accessory Organs
1.
The eyelid protects the eye
from foreign objects and is
made up of the thinnest skin
of the body lined with
conjunctiva.

2.
3.
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The lacrimal apparatus produces
tears that lubricate and cleanse the
eye.
a.
Two small ducts drain tears
into the nasal cavity.
b.
Tears also contain an
antibacterial enzyme.
The extrinsic muscles of the eye
attach to the sclera and move the
eye in all directions.

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
C.
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Structure of the Eye
1.
The eye is a fluid-filled hollow
sphere with three distinct
layers, or tunics.

2.
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Outer Layer
a.
The outer (fibrous) tunic is the
transparent cornea at the
front of the eye, and the white
sclera of the anterior eye.
b.
The optic nerve and blood
vessels pierce the sclera at the
posterior of the eye.

3.
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Middle Layer
a.
The middle, vascular tunic
includes the choroid coat,
ciliary body, and iris.
b.
The choroid coat is vascular
and darkly pigmented and
performs two functions: to
nourish other tissues of the
eye and to keep the inside of
the eye dark.
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c. The ciliary body forms a ring
around the front of the eye and
contains ciliary muscles and
suspensory ligaments that hold the
lens in position and change its
shape (focus).
d. The ability of the lens to adjust
shape to facilitate focusing is called
accommodation.
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e. The iris is a thin, smooth muscle
that adjusts the amount of light
entering the pupil, a hole in its
center.
i.
The iris has a circular set of
and a radial set of muscle
fibers.
f. The anterior chamber (between the
cornea and iris) and the posterior
chamber (between the iris and
vitreous body and housing the lens)
make up the anterior cavity, which
is filled with aqueous humor.
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
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g. The aqueous humor circulates from
one chamber to the other through
the pupil.
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4. Inner Layer
a.
The inner tunic consists of the
retina, which contains
photoreceptors; the inner tunic
covers the back side of the eye
to the ciliary body.
b.
In the center of the retina is the
macula lutea with the fovea
centralis in its center, the point
of sharpest vision in the retina.
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c.
d.
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Medial to the fovea centralis is
the optic disk, where nerve
fibers leave the eye and
where there is a blind spot.
The large cavity of the eye is
filled with vitreous humor.
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D. Light Refraction
1.
Light waves must bend to be
focused, a phenomenon
called
refraction.
2.
Both the cornea and lens bend
light waves that are focused
on
the retina, as do the
two humors
to a lesser
degree.
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E. Visual Receptors
1.
Two kinds of modified neurons
comprise the visual receptors;
elongated rods and blunt-shaped
cones.
2.
Rods are more sensitive to light and
function in dim light; they produce
colorless vision.
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3. Cones provide sharp images in bright
light and enable us to see in color.
a.
To see something in detail, a
person moves the eyes so the
image falls on the fovea centralis,
which contains the highest
concentration of cones.
b.
The proportion of cones decreases
with distance from the fovea
centralis.
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F. Visual Pigments
1.
The light-sensitive pigment in rods
is rhodopsin, which breaks down
into a protein, opsin, and retinal
(from vitamin A) in the presence of
light.
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a.
b.
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Decomposition of rhodopsin
activates an enzyme that
initiates changes in the rod
cell membrane, generating a
nerve impulse.
Nerve impulses travel away
from the retina and are
interpreted as vision.
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2. The light-sensitive pigments in cones are
also proteins; there are three sets of
cones, each containing a different visual
pigment.
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
a.
b.
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The wavelength of light determines
the color perceived from it; each of
the three pigments is sensitive to
different wavelengths of light.
The color perceived depends upon
which sets of cones the light
stimulates: if all three sets are
stimulated, the color is white; if
none are stimulated, the color is
black.
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G. Visual Nerve Pathways
1.
The axons of ganglion cells leave
the eyes to form the optic nerves.
2.
Fibers from the medial half of the
retina cross over in the optic
chiasma.
3.
Impulses are transmitted to the
thalamus and then to the visual
cortex of the occipital lobe.
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