Transcript Senses - Heartland Community College

Hole’s Human Anatomy
and Physiology
Twelfth Edition
Shier w Butler w Lewis
Chapter
12
Nervous System III: Senses
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1
12.1: Introduction
• General senses
• Receptors that are widely distributed throughout the
body
• Skin, various organs and joints
• Special senses
• Specialized receptors confined to structures in the head
• Eyes, ears, nose and mouth
2
12.2: Receptors, Sensation,
and Perception
• Sensory receptors
• Specialized cells or multicellular structures that collect
information from the environment
• Stimulate neurons to send impulses along sensory fibers
to the brain
• Sensation
• A feeling that occurs when brain becomes aware of a
sensory impulse
• Perception
• A person’s view of the stimulus; the way the brain
interprets the information
3
Pathways From Sensation to Perception
(Example of an Apple)
4
Receptor Types
• Chemoreceptors
• Respond to changes in chemical concentrations
• Pain receptors (nociceptors)
• Respond to tissue damage
• Thermoreceptors
• Respond to changes in temperature
• Mechanoreceptors
• Respond to mechanical forces
• Photoreceptors
• Respond to light
5
Sensory Impulses
• Stimulation of receptor causes local change in its receptor potential
• A graded electrical current is generated that reflects intensity of stimulation
• If receptor is part of a neuron, the membrane potential may generate an
action potential
• If receptor is not part of a neuron, the receptor potential must be transferred
to a neuron to trigger an action potential
• Peripheral nerves transmit impulses to CNS where they are analyzed and
interpreted in the brain
6
Sensations and Perception
• Projection
• Process in which the brain projects the sensation back
to the apparent source
• It allows a person to pinpoint the region of
stimulation
7
Sensory Adaptation
• Ability to ignore unimportant stimuli
• Involves a decreased response to a particular stimulus
from the receptors (peripheral adaptation) or along the
CNS pathways leading to the cerebral cortex (central
adaptation)
• Sensory impulses become less frequent and may cease
• Stronger stimulus is required to trigger impulses
8
12.3: General Senses
• Senses associated with skin, muscles, joints and viscera
• Three (3) groups:
• Exteroceptive senses (exteroceptors)
• Senses associated with body surface such as touch, pressure,
temperature, and pain
• Visceroceptive senses (interoceptors)
• Senses associated with changes in the viscera such as blood
pressure stretching blood vessels and ingestion of a meal
• Proprioceptive senses
• Senses associated with changes in muscles and tendons such
as at joints
9
Touch and Pressure Senses
Free nerve endings
• Common in epithelial
tissues (most common
receptor in the body)
• Simplest receptors
• Sense itching
Tactile (Meissner’s) corpuscles
• Abundant in hairless portions of
skin and lips
• Detect fine touch; distinguish
between two points on the skin
Lamellated (Pacinian) corpuscles
• Common in deeper subcutaneous
tissues, tendons and ligaments
• Detect heavy pressure and vibrations
10
Touch and Pressure Receptors
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Free nerve
endings
Section of
skin
Epithelial
cells
Epidermis
(a)
Sensory
nerve fiber
Epithelial
cells
Dermis
Tactile (Meissner’s)
corpuscle
(touch receptor)
(b)
Sensory nerve
fiber
Lamellated
(Pacinian) corpuscle
(pressure receptor)
Connective tissue
cells
Sensory nerve
fiber
(c)
b, c: © Ed Reschke
11
Temperature Senses
• Warm receptors
• Sensitive to temperatures above 25oC (77o F)
• Unresponsive to temperature above 45oC (113oF)
• Cold receptors
• Sensitive to temperatures between 10oC (50oF) and 20oC
(68oF)
• Pain receptors
• Respond to temperatures below 10oC
• Respond to temperatures above 45oC
12
Sense of Pain
• Free nerve endings
• Widely distributed
• Nervous tissue of brain lacks pain receptors – brain surgery
does not hurt!
• Stimulated by tissue damage, chemical, mechanical forces, or
extremes in temperature
• Adapt very little, if at all
13
Visceral Pain
• Pain receptors are the only receptors in viscera whose
stimulation produces sensations
• Pain receptors respond differently to stimulation
• Pain receptors are not well localized
• Phantom limb pain
• Pain receptors may feel as if coming from some other part of
the body -- known as referred pain…
14
Referred Pain
• May occur due to sensory impulses from two regions
following a common nerve pathway to brain
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Liver and
gallbladder
Lung and diaphragm
Liver and
gallbladder
Heart
Stomach
Pancreas
Small
intestine
Appendix
Ovary
(female)
Colon
Kidney
Ureter
Urinary bladder
15
Pain Nerve Pathways
• Acute pain fibers
• Chronic pain fibers
• A-delta fibers
• C fibers
• Thin, myelinated
• Thin, unmyelinated
• Conduct impulses rapidly
• Conduct impulses more
• Associated with sharp pain
slowly
• Well localized
• Associated with dull,
aching pain
• Difficult to pinpoint
16
Regulation of Pain Impulses
• Thalamus
• Allows person to be aware of pain
• Cerebral cortex
• Judges intensity of pain
• Locates source of pain
• Produces emotional and motor responses to pain
• Pain inhibiting substances:
• Enkephalins
• Serotonin
• Endorphins
17
Proprioception
• Mechanoreceptors
• Send information to spinal cord and CNS about body
position and length, and tension of muscles
• Main kinds of proprioceptors:
• Pacinian corpuscles – in joints
• Muscle spindles – in skeletal muscles*
• Golgi tendon organs – in tendons*
*considered to be stretch receptors
18
Stretch Receptors
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Sensory
nerve fiber
Sensory
nerve endings
Golgi tendon organ
Sensory
nerve fiber
Tendon
Intrafusal
fiber
Skeletal muscle
fiber
Muscle spindle
Skeletal muscle fiber
Connective
tissue sheath
(a)
(b)
19
19
Visceral Senses
• Receptors in internal organs
• Convey information that includes the sense of fullness
after eating a meal as well as the discomfort of intestinal
gas and the pain that signals a heart attack
20
Summary of Receptors of the
General Senses
21
12.4: Special Senses
• Sensory receptors are within large, complex sensory
organs in the head
• Smell in olfactory organs
• Taste in taste buds
• Hearing and equilibrium in ears
• Sight in eyes
22
Sense of Smell
• Olfactory receptors
• Chemoreceptors
• Respond to chemicals dissolved in liquids
• Olfactory organs
• Contain olfactory receptors and supporting epithelial
cells
• Cover parts of nasal cavity, superior nasal conchae, and a
portion of the nasal septum
23
Olfactory Receptors
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Nerve fibers within
the olfactory bulb
Olfactory Olfactory
tract
bulb
Cribriform
plate
Olfactory area of
nasal cavity
Superior nasal
concha
Nasal cavity
Cilia
(a)
Olfactory
Columnar
Cribriform
receptor cells epithelial cells plate
(b)
24
Olfactory Nerve Pathways
• Once olfactory receptors are stimulated, nerve impulses
travel through:
• Olfactory nerves
olfactory bulbs
olfactory
tracts
limbic system (for emotions) and olfactory
cortex (for interpretation)
25
Olfactory Stimulation
• Olfactory organs located high in the nasal cavity above the
usual pathway of inhaled air
• Olfactory receptors undergo sensory adaptation rapidly
• Sense of smell drops by 50% within a second after
stimulation
26
Sense of Taste
• Taste buds
• Organs of taste
• Located on papillae of tongue, roof of mouth, linings of
cheeks and walls of pharynx
• Taste receptors
• Chemoreceptors
• Taste cells – modified epithelial cells that function as
receptors
• Taste hairs –microvilli that protrude from taste cells;
sensitive parts of taste cells
27
Taste Receptors
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Papillae
Taste buds
Epithelium
of tongue
Taste cell
(a)
Taste hair
Supporting
cell
Taste
pore
(b)
Connective
tissue
Sensory
nerve fibers
28
Taste Sensations
• Four primary taste sensations
• Sweet – stimulated by carbohydrates
• Sour – stimulated by acids
• Salty – stimulated by salts
• Bitter – stimulated by many organic compounds
• Spicy foods activate pain receptors
29
Taste Nerve Pathways
• Sensory impulses from taste receptors travel along:
• Cranial nerves to
Thalamus to
Medulla oblongata to
Gustatory cortex (for interpretation)
30
Sense of Hearing
• Ear
• Organ of hearing
• Three (3) sections:
• External ear
• Middle ear
• Inner ear
31
External Ear
• Auricle
• Collects sounds waves
• External auditory meatus
• Lined with ceruminous
glands
• Carries sound to
tympanic membrane
• Terminates with
tympanic membrane
• Tympanic membrane
• Vibrates in response to
sound waves
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Auricle
Semicircular
canals
Incus
Stapes
Malleus
Cochlea
Vestibulocochlear
nerve
Oval window (under stapes)
Round window
Tympanic cavity
Tympanic
membrane
External acoustic
meatus
Auditory tube
Pharynx
32
Middle Ear
• Tympanic cavity
• Air-filled space in
temporal bone
• Auditory ossicles
• Vibrate in response to
tympanic membrane
• Malleus, incus and stapes
• Hammer, anvil and stirrup
• Oval window
• Opening in wall of
tympanic cavity
• Stapes vibrates against it to
move fluids in inner ear
Auricle
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Semicircular
canals
Incus
Stapes
Malleus
Cochlea
Vestibulocochlear
nerve
Oval window (under stapes)
Round window
Tympanic cavity
Tympanic
membrane
External acoustic
meatus
Auditory tube
Pharynx
33
Auditory Tube
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• Also known as the
Eustachian tube
• Connects middle ear to
throat
• Helps maintain equal
pressure on both sides of
tympanic membrane
• Usually closed by valvelike flaps in throat
Auricle
Semicircular
canals
Incus
Stapes
Malleus
Cochlea
Vestibulocochlear
nerve
Oval window (under stapes)
Round window
Tympanic cavity
Tympanic
membrane
External acoustic
meatus
Auditory tube
Pharynx
34
Inner Ear
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Bony labyrinth
• Complex system of labyrinths
• Osseous labyrinth
• Bony canal in
temporal bone
• Filled with perilymph
• Membranous labyrinth
• Tube within osseous
labyrinth
• Filled with endolymph
Perilymph
Membranous
labyrinth
Endolymph
Bony labyrinth
(contains perilymph)
Membranous labyrinth
(contains endolymph)
Semicircular
canals
Utricle
Saccule
Vestibular nerve
Cochlear nerve
Scala
vestibuli (cut)
Scala
tympani (cut)
Cochlear
duct (cut)
containing
endolymph
Ampullae Oval Vestibule Round Maculae
window
window
(a)
Cochlea
35
Inner Ear
• Three (3) parts of labyrinths:
• Cochlea
• Functions in hearing
• Semicircular canals
• Functions in dynamic
equilibrium
• Vestibule
• Functions in static
equilibrium
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Bony labyrinth
Perilymph
Membranous
labyrinth
Endolymph
Bony labyrinth
(contains perilymph)
Membranous labyrinth
(contains endolymph)
Semicircular
canals
Utricle
Saccule
Vestibular nerve
Cochlear nerve
Scala
vestibuli (cut)
Scala
tympani (cut)
Cochlear
duct (cut)
containing
endolymph
Ampullae Oval Vestibule Round Maculae
window
window
(a)
Cochlea
36
Cochlea
• Scala vestibuli
• Upper compartment
• Leads from oval
window to apex of
spiral
• Part of bony labyrinth
• Scala tympani
• Lower compartment
• Extends from apex of
the cochlea to round
window
• Part of bony labyrinth
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Stapes vibrating in
oval window
Helicotrema
Scala vestibuli
filled with perilymph
Vestibular
membrane
Basilar
membrane
Scala tympani
filled with
perilymph
Round window
Membranous
labyrinth
Cochlear duct
filled with endolymph
37
Cochlea
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• Cochlear duct
• Portion of
membranous labyrinth
in cochlea
• Vestibular membrane
• Separates cochlear
duct from scala
vestibuli
• Basilar membrane
• Separates cochlear
duct from scala
tympani
Scala vestibuli
(contains perilymph)
Vestibular membrane
Branch of
cochlear
nerve
Cochlear duct
(contains endolymph)
Spiral organ (organ of Corti)
Basilar membrane
Scala tympani
(contains perilymph)
(a)
38
Animation:
Effect of Sound Waves
on Cochlear Structures
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39
Organ of Corti
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• Group of hearing receptor
cells (hair cells)
• On upper surface of basilar
membrane
• Different frequencies of
vibration move different parts
of basilar membrane
• Particular sound frequencies
cause hairs of receptor cells to
bend
• Nerve impulse generated
Scala vestibuli
(contains perilymph)
Vestibular membrane
Cochlear duct
(contains endolymph)
Spiral organ (organ of Corti)
Branch of
cochlear
nerve
Basilar membrane
Scala tympani
(contains perilymph)
(a)
Tectorial
membrane
Hair cells
40
(b)
Branch of
cochlear nerve
Nerve
fibers
Supporting
cells
Basilar
membrane
Organ of Corti
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Cochlear duct
Tectorial membrane
Scala tympani
Hair cells
Basilar
membrane
(a)
(b)
a: © John D. Cunningham/Visuals Unlimited; b: © Fred Hossler/Visuals Unlimited
41
Auditory Nerve Pathways
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Auditory cortex
(temporal lobe)
Thalamus
Medial geniculate
body of thalamus
Midbrain
Pons
Cochlear
nuclei
Superior
olivary
nucleus
Medulla
oblongata
Vestibulocochlear
nerve
42
Summary of the Generation of
Sensory Impulses from the Ear
43
Sense of Equilibrium
• Static equilibrium
• Vestibule
• Senses position of
head when body is not
moving
• Dynamic Equilibrium
• Semicircular canals
• Senses rotation and
movement of head and
body
44
Vestibule
• Utricle
• Communicates with
saccule and membranous
portion of semicircular
canals
• Saccule
• Communicates with
cochlear duct
• Macula
• Hair cells of utricle and
saccule
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Ampullae of
semicircular
canals
Vestibulocochlear
nerve
Cochlea
Utricle
Cochlear
duct
Maculae Saccule Vestibule
45
Macula
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• Responds to changes
in head position
• Bending of hairs
results in generation of
nerve impulse
Hairs of
hair cells bend
Gelatinous
material sags
Otoliths
Macula
of utricle
Hair cells
Sensory nerve fiber
Gravitational
force
Supporting cells
46
(a) Head upright
(b) Head bent forward
Semicircular Canals
• Three (3) canals at right angles
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• Ampulla
• Swelling of membranous
Vestibulocochlear
labyrinth that communicates
nerve
Ampullae of
Cochlea
semicircular
Utricle
with the vestibule
canals
Cochlear
duct
• Crista ampullaris
• Sensory organ of ampulla
• Hair cells and supporting cells
• Rapid turns of head or body
stimulate hair cells
Maculae Saccule Vestibule
47
Crista Ampullaris
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Endolymph
Semicircular canal
Cupula
Crista
ampullaris
(a) Head in still position
Ampulla
Crista ampullaris
Hairs
Hair cell
Supporting cells
Sensory nerve fibers
(b) Head rotating
(c)
48
Sense of Sight
• Visual accessory organs
• Eyelids
• Lacrimal apparatus
• Extrinsic eye muscles
49
Eyelid
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• Palpebra
• Composed of four (4) layers:
• Skin
• Muscle
• Connective tissue
• Conjunctiva
• Orbicularis oculi – closes eyelid
• Levator palpebrae superioris –
opens eyelid
• Tarsal glands – secrete oil onto
eyelashes
• Conjunctiva – mucous
membrane; lines eyelid and covers
portion of eyeball
Tendon of levator
palpebrae superioris
Superior
rectus
Orbicularis
oculi
Eyelid
Tarsal glands
Eyelash
Cornea
Conjunctiva
Inferior
rectus
50
Lacrimal Apparatus
• Lacrimal gland
• Lateral to eye
• Secretes tears
Lacrimal gland
• Canaliculi
• Collect tears
Superior and
inferior canaliculi
• Lacrimal sac
Lacrimal sac
• Collects from
canaliculi
Nasolacrimal
• Nasolacrimal duct
duct
• Collects from lacrimal
sac
• Empties tears into nasal
cavity
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51
Extrinsic Eye Muscles
• Superior rectus
• Rotates eye up and
medially
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Medial Superior
rectus rectus
Superior
oblique
• Inferior rectus
• Rotates eye down
and medially
• Medial rectus
• Rotates eye
medially
Lateral
rectus
(cut)
Inferior rectus
Inferior oblique
52
Extrinsic Eye Muscles
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• Lateral rectus
• Rotates eye
laterally
Medial Superior
rectus rectus
Superior
oblique
• Superior oblique
• Rotates eye down
and laterally
• Inferior oblique
• Rotates eye up and
laterally
Lateral
rectus
(cut)
Inferior rectus
Inferior oblique
53
Structure of the Eye
• Hollow
• Spherical
• Wall has three (3) layers:
• Outer fibrous tunic
• Middle vascular tunic
• Inner nervous tunic
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Lateral rectus
Retina
Ciliary body
Suspensory
ligaments
Choroid coat
Sclera
Vitreous humor
Iris
Lens
Fovea centralis
Pupil
Cornea
Aqueous
humor
Anterior
cavity
Anterior
chamber
Posterior
chamber
Optic nerve
Optic disc
Posterior cavity
Medial rectus
54
Outer Tunic
• Cornea
• Anterior portion
• Transparent
• Light transmission
• Light refraction
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Lateral rectus
Retina
Ciliary body
Suspensory
ligaments
Vitreous humor
Iris
Lens
Fovea centralis
Pupil
• Sclera
• Posterior portion
• Opaque
• Protection
Choroid coat
Sclera
Cornea
Aqueous
humor
Anterior
cavity
Anterior
chamber
Posterior
chamber
Optic nerve
Optic disc
Posterior cavity
Medial rectus
55
Middle Tunic
• Iris
• Anterior portion
• Pigmented
• Controls light intensity
• Ciliary body
• Anterior portion
• Pigmented
• Holds lens
• Moves lens for focusing
• Choroid coat
• Provides blood supply
• Pigments absorb extra light
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Lateral rectus
Retina
Ciliary body
Suspensory
ligaments
Choroid coat
Sclera
Vitreous humor
Iris
Lens
Fovea centralis
Pupil
Cornea
Aqueous
humor
Anterior
cavity
Anterior
chamber
Posterior
chamber
Optic nerve
Optic disc
Posterior cavity
Medial rectus
56
Anterior Portion of Eye
• Filled with aqueous humor
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Cornea
Anterior chamber
Iris
Posterior
chamber
Ciliary process
Suspensory
ligaments
Ciliary muscles
Ciliary
body
Conjunctiva
Vitreous
humor
Lens
Sclera
57
Lens
• Transparent
• Biconvex
• Lies behind iris
• Largely composed of
lens fibers
• Elastic
• Held in place by
suspensory ligaments of
ciliary body
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Cornea
Anterior chamber
Iris
Posterior
chamber
Ciliary process
Suspensory
ligaments
Ciliary muscles
Ciliary
body
Conjunctiva
Vitreous
humor
Lens
Sclera
58
Ciliary Body
• Forms internal ring around the
front of the eye
• Ciliary processes – radiating
folds
• Ciliary muscles – contract and
relax to move lens
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Ciliary processes
of ciliary body
Suspensory
ligaments
Lens
Retina
Choroid coat
Sclera
59
Accommodation
• Changing of lens shape to view objects
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Ciliary muscle
fibers contracted
Suspensory
ligaments relaxed
Lens thick
(a)
Ciliary muscle
fibers relaxed
Suspensory
ligaments taut
Lens thin
60
(b)
Iris
• Composed of
connective tissue and
smooth muscle
• Pupil is hole in iris
• Dim light stimulates
radial muscles and
pupil dilates
• Bright light
stimulates circular
muscles and pupil
constricts
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Sympathetic
motor nerve
fiber
In dim light
Radially arranged
Smooth muscle fibers
of the iris
Parasympathetic
ganglion
Circularly arranged
smooth muscle fibers
of the iris
Pupil
In normal light
Parasympathetic
motor nerve fiber
In bright light
61
Aqueous Humor
• Fluid in anterior cavity of eye
• Secreted by epithelium on inner surface of the ciliary body
• Provides nutrients
• Maintains shape of anterior portion of eye
• Leaves cavity through Canal of Schlemm
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Cornea
Aqueous humor
Anterior
chamber
Iris
Scleral venous sinus
(canal of Schlemm)
Lens
Sclera
Ciliary process
Ciliary
body
Ciliary muscles
Vitreous humor
Posterior
chamber
62
Inner Tunic
• Retina
• Contains visual receptors
• Continuous with optic nerve
• Ends just behind margin of the ciliary body
• Composed of several layers
• Macula lutea – yellowish spot in retina
• Fovea centralis – center of macula lutea; produces
sharpest vision
• Optic disc – blind spot; contains no visual receptors
• Vitreous humor – thick gel that holds retina flat against
choroid coat
63
Posterior Cavity
• Contains vitreous humor – thick gel that holds retina flat
against choroid coat
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Lateral rectus
Retina
Ciliary body
Suspensory
ligaments
Choroid coat
Sclera
Vitreous humor
Iris
Lens
Fovea centralis
Pupil
Cornea
Aqueous
humor
Anterior
cavity
Anterior
chamber
Posterior
chamber
Optic nerve
Optic disc
Posterior cavity
Medial rectus
64
Major Groups of Retinal Neurons
• Receptor cells, bipolar cells, and ganglion cells - provide pathway
for impulses triggered by photoreceptors to reach the optic nerve
• Horizontal cells and amacrine cells – modify impulses
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Sclera
Pigmented
choroid
coat
Retinal pigment
epithelium
Rod
Cone
Receptor cells
Horizontal cell
Retina
Bipolar neuron
Amacrine cell
Layer of
connecting
neurons
Ganglion cell
Nerve fibers
Vitreous humor
Impulses
to optic
nerve
65
Light waves
Layers of the Eye
66
Light Refraction
• Refraction
• Bending of light
• Occurs when light waves pass at an oblique angle into
mediums of different densities
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Perpendicular line
Air
Light wave
Glass
Refracted
light wave
67
Focusing On Retina
• As light enters eye, it is refracted by:
• Convex surface of cornea
• Convex surface of lens
• Image focused on retina is upside down and reversed from left
to right
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Light waves
Image
Retina
Object
Cornea
68
Types of Lenses
• Convex lenses cause
light waves to converge
• Concave lenses cause
light waves to diverge
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Light
wave
Air
Convex
surface
Concave
surface
Glass
Converging
light waves
(a)
Diverging
light waves
(b)
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12.6 Clinical Application
Refraction Disorders
• Concave lens corrects
nearsightedness
• Convex lens corrects
farsightedness
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Lens
Point
of focus
Uncorrected
point of focus
Cornea
Light waves
Light waves
(a) Eye too long (myopia)
Point
of focus
Concave lens
(a)
Corrected
point of focus
Light waves
Retina
Uncorrected
point of focus
(b) Normal eye
Point
of focus
Light waves
Convex lens
(c) Eye too short (hyperopia)
(b)
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Corrected
point of focus
Visual Receptors
• Rods
• Cones
• Long, thin projections
• Short, blunt projections
• Contain light sensitive
• Contain light sensitive
pigment called rhodopsin
pigments called erythrolabe,
• Hundred times more sensitive chlorolabe, and cyanolabe
to light than cones
• Provide vision in bright
• Provide vision in dim light
light
• Produce colorless vision
• Produce sharp images
• Produce outlines of objects
• Produce color vision
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Rods and Cones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Retinal pigment
epithelium
Cones
Rods
Single sensory
nerve fiber
(a)
Many sensory
nerve fibers
(b)
Rod
Cone
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(c)
c: © Frank S. Werblin, PhD.
Visual Pigments
• Rhodopsin
• Light-sensitive pigment in rods
• Decomposes in presence of light
• Triggers a complex series of
reactions that initiate nerve
impulses
• Impulses travel along optic nerve
• Pigments on cones
• Each set contains different lightsensitive pigment
• Each set is sensitive to different
wavelengths
• Color perceived depends on which
sets of cones are stimulated
• Erythrolabe – responds to red
• Chlorolabe – responds to green
• Cyanolabe – responds to blue
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Stereoscopic Vision
• Provides perception of distance and depth
• Results from formation of two slightly different retinal images
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Light
waves
Left eye
Right eye
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Visual Nerve Pathway
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Eye
Optic
nerve
Fibers from
nasal (medial) half
of each retina
crossing over
Optic
chiasma
Optic tract
Lateral
geniculate
body of
thalamus
Optic
radiations
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Visual cortex of
occipital lobe
12.5: Lifespan Changes
• Age related hearing loss due to:
• Damage of hair cells in organ of Corti
• Degeneration of nerve pathways to the brain
• Tinnitus
• Age-related visual problems include:
• Dry eyes
• Floaters (crystals in vitreous humor)
• Loss of elasticity of lens
• Glaucoma
• Cataracts
• Macular degeneration
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Important Points in Chapter 12:
Outcomes to be Assessed
12.1: Introduction
 Explain the difference between general senses and special senses.
12.2: Receptors, Sensation, and Perception
 Name the five types of receptors and state the function of each.
 Explain how receptors stimulate sensory impulses.
 Explain how a sensation is produced.
12.3: General Senses
 Distinguish between general and special senses.
 Describe the differences among receptors associated with the senses
of touch, pressure, temperature, and pain.
 Describe how the sensation of pain is produced.
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Important Points in Chapter 12:
Outcomes to be Assessed
 Explain the importance of stretch receptors in muscles and tendons.
12.4: Special Senses
 Explain the relationship between the senses of smell and taste.
 Name the parts of the ear and the function of each part.
 Distinguish between static and dynamic equilibrium.
 Name the parts of the eye and the function of each part.
 Explain how the eye refracts light.
 Explain how the brain perceives depth and distance.
 Draw a diagram of the visual nerve pathways.
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