Transcript Special_Senses__Ch_8__S2015

Special Senses
Chapter 8
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Outline
Types of Sensory Receptors
Functions of Sensory Receptors
Sensations and Perceptions
Cutaneous Receptors
Sense of Position in Space- Posture
Sense of Taste
Sense of Smell
Sense of Hearing
Sense of Balance (Equilibrium)
Sense of Vision
Homeostasis
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Types of Sensory Receptors
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Sensory receptors are specialized to detect certain
types of stimuli. Can be modified dendrites of
sensory neurons or specialized cells that release
neurotransmitters that stimulate nearby sensory
neuron.
– Exteroceptors detect stimuli outside the body.
 Taste, smell, vision.
 Indirectly linked to homeostasis.
– Interoceptors detect stimuli inside the body.
 Blood pressure, blood volume, pH.
 Directly linked to homeostasis.
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Subtypes of Sensory Receptors
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Chemoreceptors.
– Respond to chemical substances in the
immediate vicinity.
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Pain Receptors (Nociceptors).
 Respond to chemicals released by damaged
tissue from intense pressure, temperature, light.
Photoreceptors.
– Respond to light energy.
Mechanoreceptors.
– Stimulated by mechanical forces.
Thermoreceptors.
– Stimulated by changes in temperature.
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Functions of Sensory Receptors
To provide information for the proper
maintenance of the body.
Significant contributors to homeostasis.
Interoceptors are directly involved by
monitoring vital functions such as blood
pressure and pH.
Exteroceptors are indirectly involved by
monitoring our external environment, but are
just as important; we see the oncoming car
and get out of the way; we put a coat on so
as not to freeze to death.
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Sensations and Perceptions
Sensation occurs when nerve impulses
arrive at the cerebral cortex of the brain.
Perception occurs when the cerebral cortex
interprets the meaning of sensations.
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Sensory receptors initiate nerve impulses;
perception depends on the part of the brain
receiving the nerve impulses.
Strength of stimulus related to frequency of
firing of nerve impulses.
Have integration at level of sensory receptor,
spinal cord, and brain.
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Cutaneous Receptors
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The dermis contains cutaneous receptors,
which include:
– Mechanoreceptors.
 Sensitive to touch.
– Nociceptors.
 Sensitive to pain.
– Thermoreceptors.
 Sensitive to temperature.
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Cutaneous Receptors
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Sense of Position in Space- Posture
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Proprioceptors are mechanoreceptors that
help determine limb position in space by
detecting the degree of muscle relaxation,
stretch of tendons, and movement of
ligaments.
– Muscle spindles detect the stretching of
muscles; act to increase the degree of
muscle contraction.
– Tendon receptors detect the tension in the
tendons of muscles; act to decrease it.
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Muscle Spindle
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Skeletal
muscle
Sensory
neurons
of muscle
spindle
Tendon
connecting
bone to
muscle
Muscle spindle
Tendon
receptor
Sensory neuron
of tendon
stretch receptor
Tendon
Bone
a) Muscle spindle. A muscle spindle responds to
muscle length. Passive stretch of a muscle stretches
the muscle spindle, stimulating mechanoreceptors in
the nerve endings of the sensory neurons. Conversely,
muscle contraction shortens the muscle spindle,
reducing muscle spindle mechanoreceptor stimulation.
© 2012 Pearson Education, Inc.
b) Tendon receptor. A tendon receptor responds to
tension in tendons. When a muscle contracts and
also when it is stretched passively, tension on the
tendon increases, activating tendon receptors.
Figure 12.3
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Sense of Taste
Chemoreceptors for taste are found in taste
buds located primarily embedded in tongue
epithelium.
 Five primary tastes.
 Sweet.
 Sour.
 Salty.
 Bitter.
 Umami
 Weighted average integrated response.
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Figure 8.19 Location and structure of taste buds.
Sense of Taste
Epiglottis
Epithelium of tongue
Palatine tonsil
Lingual tonsil
Surface of
the tongue
Vallate papilla
Taste bud
Connective
tissue
Gustatory
(taste) cell
Basal
cell
Sensory
nerve
fiber
Fungiform
papillae
(a)
Taste buds
(b)
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Gustatory hairs
(microvilli) emerging
from a taste pore
(c)
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Sense of Smell
Dependent on chemoreceptors on olfactory
cells located within olfactory epithelium high
in the roof of the nasal cavity.
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Each olfactory cell (sensory neuron) has only
one type of chemoreceptor; there are ~1500
types; odor made up of multiple molecules;
multiple different cells stimulated- integration.
Olfactory bulbs have direct connections with the
limbic system and its centers for emotions and
memory.
Sense of taste and smell work together to
create a combined effect.
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Sense of Smell
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olfactory bulb
neuron
olfactory tract
frontal lobe of
cerebral hemisphere
olfactory bulb
olfactory epithelium
nasal cavity
odor
molecules
bone of
skull
sensory
nerve fibers
olfactory
epithelium
a.
supporting olfactory
cell
cell
b.
olfactory cilia of
olfactory cell
odor molecules
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Sense of Hearing
Anatomy of the Ear.
– Outer ear: pinna; auditory canal.
– Middle ear: tympanic membrane; malleus,
incus, and stapes (ossicles); round
window; oval window.
– Inner ear: semicircular canals, vestibule,
and cochlea.
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Figure 8.12 Anatomy of the ear.
External (outer) ear
Middle ear
Internal (inner) ear
Vestibulocochlear
nerve
Auricle
(pinna)
Semicircular
canals
Oval window
Cochlea
Vestibule
Round window
Pharyngotympanic
(auditory) tube
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Tympanic
membrane
(eardrum) Hammer Anvil Stirrup
(malleus) (incus) (stapes)
External acoustic
meatus
Auditory ossicles
(auditory canal)
Frequency
(cycles/sec)
Soft,
low tone
Loud,
low tone
Soft,
high tone
Amplitude
Loud,
high tone
0
1
2
3
4
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Time (msec)
© 2012 Pearson Education, Inc.
Figure 12.8
Loudness determined by
number of hair cells
stimulated.
High-frequency
sounds
Oval
window
Sound
wave
Round window
Auditory tube
Low-frequency
sounds
Pitch determined by
region of basilar
membrane stimulated.
a) The cochlea as it might appear if
it were uncoiled. Higher-frequency
sounds are converted to impulses
near the oval window, whereas
lower-frequency sounds are converted
near the tapered tip.
Vestibular
canal
Organ
of Corti
Cochlear
duct
Hairs of
hair cells
Tectorial membrane
Hair cells
To auditory
nerve
Hair
cells
Tympanic
canal
Basilar
membrane
b) A cross section through the cochlea.
Pressure waves passing from the
vestibular canal to the tympanic canal
through the cochlear duct cause the basilar
membrane to vibrate.
c) A section through part of the cochlea,
showing hair cells with their hairs embedded
in the tectorial membrane. Vibration of the
basilar membrane bends the hairs, ultimately
generating impulses in sensory neurons.
© 2012 Pearson Education, Inc.
d) SEM ( 4,200) of healthy hair cells.
Figure 12.10
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“Hairs” of
hair cell
Neurotransmitter
More
neurotransmitter
Less
neurotransmitter
Sensory
neuron
Action
potentials
a) Hair cell at rest.
b) Hairs moving in one
direction.
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c) Hairs moving in other
direction.
Figure 12.11
Sense of Balance (Equilibrium)
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Rotational Equilibrium
– Cupula movement within the semicircular
canals detects rotation and/or angular
movement of the head.
Gravitational Equilibrium.
– Movement of the otolithic membrane
within the utricle and the saccule detects
position of the head in the vertical and
horizontal planes compared to gravity and
detects acceleration.
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The inner ear: Balance
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semicircular
canals
receptor in ampulla
endolymph
Vestibular nerve
ampullae
cochlea
utricle
saccule
endolymph
cupula
otoliths
stereocilia
otolithic
membrane
Hair cell
hair cell
Supporting cell
supporting
cell
vestibular
nerve
Vestibular nerve
flow of endolymph
Flow of otolithic
membrane
The
mechanoreceptors
of the inner ear and
the sense of
balance.
a. Rotational equilibrium: receptors in ampullae of semicircular canal
kinocilium
stereocilia
b. Gravitational equilibrium: receptors in utricle and saccule of vestibule
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Sense of Vision
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The eyeball has three layers.
– Sclera.
– Choroid.
– Retina.
The retina contains two types of
photoreceptors.
– Rod cells.
– Cone cells.
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Anatomy of the Human Eye
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Anatomy of the Human Eye (Cont.)
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The Lacrimal Apparatus & Conjunctiva
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Lacrimal glands- lateral end of each eye; release tears
continuously, flush across eyes; contains lysozymeantibacterial protein
Lacrimal canaliculi- channels that help drain tears
Lacrimal sac- drains tears into nasolacrimal duct
Nasolacrimal duct- tube that conducts tears to nasal
cavity
Conjunctiva- thin membranes line eyelids & covers
surface of eyes; produces mucus, helps lubricate eye
movements & keeps surface moist
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Figure 8.2 Accessory structures of the eye.
Lacrimal
gland
Lacrimal
gland
Excretory duct
of lacrimal gland
Conjunctiva
Anterior
aspect
Eyelid
Eyelashes
(a)
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Excretory ducts
of lacrimal gland
Lacrimal canaliculus
Nasolacrimal duct
Inferior meatus
of nasal cavity
Tarsal
glands
Nostril
Eyelid
(b)
Lacrimal sac
Focusing
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Observing object, light rays pass through
the cornea, the aqueous humor, the pupil,
the lens, the vitreous humor, and are
focused on the retina.
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Focusing involves the cornea, the lens and the
humors.
Focusing for close objects (accommodation)
involves the ciliary muscles and the changing
shape of the lens.
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Focusing
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Figure 8.9 Relative convexity of the lens during focusing for distant and close vision.
Retina
Light from distant source
Focal point
(a)
Light from near source
Focal point
Retina
(b)
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Photoreceptors
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Vision begins once light has been focused on the
photoreceptors in the retina.
– Rod cells; black and white vision; very sensitive
to light; provide night and peripheral vision.
– Cone cells allow detection of fine detail and
color.
 Color vision depends on three different kinds
of cones which are sensitive to different
wavelengths (kinds of light); blue, green, and
red light.
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Cone Sensitivity to Light
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Photoreceptors in the Eye
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Integration of Visual Signals in the Retina
The retina has three layers.
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Layer closest to choroid contains rod cells and cone
cells.
Middle layer contains bipolar cells.
Innermost layer contains ganglion cells.
Rod and cone cells in back of retina thus
light must penetrate to the back before they
are stimulated.
Many rod cells connected to one ganglion
cell.
One cone cell connected to one ganglion
cell (within fovea centralis).
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Integration of Visual Signals in the Retina
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Integration of Visual Signals in the Brain
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The visual pathway begins in the retina and
passes through the thalamus before reaching the
cerebral cortex.
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The visual fields from both eyes overlap allow you to
see depth & around edges (three-dimensional vision).
The pathway and visual cortex take the visual field
apart, possibly to extract more information like color,
form, motion.
The cortex rebuilds it so we correctly perceive the field
and with possibly a better understanding of it.
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Figure 8.11 Visual fields of the eyes and visual pathway to the brain.
Fixation point
Right eye
Left eye
Optic
nerve
Optic
tract
Optic
chiasma
Optic
radiation
Thalamus
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Occipital lobe
(visual cortex)
Integration of Visual Signals in the Brain
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Abnormalities of the Eye
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Color blindness.
– Particular type of cone is lacking.
Distance Vision
– Nearsighted.
 Elongated eyeball.
– Farsighted.
 Shortened eyeball.
Astigmatism.
– Uneven cornea.
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Focal plane
a) The normal eye.
Correction
Concave lens
b) Nearsightedness (myopia). Nearsighted persons can see near
objects clearly, but distant objects are out of focus because the focal
point is in front of the retina.
Convex lens
c) Farsightedness (hyperopia). Farsighted persons can see distant
objects clearly, but near objects are out of focus.
d) Astigmatism. Astigmatism is due to an abnormal curvature of either
the cornea or the lens.
© 2012 Pearson Education, Inc.
Figure 12.17
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Homeostasis
To provide information for the proper
maintenance of the body.
Significant contributors to homeostasis.
Interoceptors are directly involved by
monitoring vital functions such as blood
pressure and pH.
Exteroceptors are indirectly involved by
monitoring our external environment, but are
just as important; we see the oncoming car
and get out of the way; we put a coat on so
as not to freeze to death.
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Need to Know
1.
Types of Sensory Receptors
Exteroceptors
Interoceptors
A.
B.
2.
Subtypes of Sensory Receptors
Chemo
A.
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B.
C.
D.
3.
Pain
Photo
Mechano
Thermo
Function in Homeostasis of Sensory Receptor
A.
B.
C.
Proper functioning of body
Interoceptors monitor vital functions
Exteroceptors monitor external environment
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Need to Know (Cont.)
Difference Between Sensation and
Perception
4.
A.
B.
C.
D.
Sensation: nerve impulses to the brain
Perception: the meaning of sensations
Part of perception is strength: comes from frequency
Part of perception is integration: occurs at receptors,
spinal cord, brain
Sense of Vision
5.
A.
B.
C.
D.
Basic anatomy including lacrimal apparatus & conjunctiva
Focusing: how it works
Photoreceptors: rod and cone cells; what they are
sensitive to
Integration of visual signals: many rod cells, one ganglion
cell; one cone cell, one ganglion cell
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Need to Know (Cont.)
6.
7.
Sense of Hearing
A.
Basic anatomy
B.
How sound is transferred to cochlea: malleus,
incus, stapes
C.
How Organ of Corti works: hair cells and
basilar membrane
Sense of Smell
A.
Basic anatomy
B.
Each olfactory cell has only one
chemoreceptor type
C.
Odor involves multiple cell stimulation;
integration
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Need to Know (Cont.)
Sense of Taste
8.
A.
Taste cells respond to sweet, sour, salty, bitter, umami
Integration of incoming signals with sense of smell
B.
C.
9.
Sense of Position in Space
A.
B.
10.
Basic anatomy
Basic anatomy
Proprioceptors: sensitive to stretch; tell brain where
our limbs are
Sense of Balance (Equilibrium)
A.
B.
Rotational Equilibrium: cupula in semicircular
channels
Gravitational Equilibrium: otolithic membrane in utricle
and saccule of vestibule
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