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Chapter 11
Sense Organs
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Sensory Receptors
• Some combine with muscle and tissue to
form sense organs
• Most consist of specialized nerve cells or
nerve endings
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Sensory Receptors (cont’d)
• Sensory receptors transmit information
about
– Type of stimulus
– Location of stimulus
– Intensity of stimulus
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Classification of Receptors
• Chemoreceptors
• Mechanoreceptors
• Thermoreceptors
• Nociceptors
• Photoreceptors
• Proprioceptors
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Question
Nociceptors respond to:
A. various chemicals inside and outside
the body.
B. pressure, stretch, or vibration.
C. pain from tissue damage.
D. changes in temperature.
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Answer
Correct answer: C
Rationale:
• Chemoreceptors react to chemicals.
• Mechanoreceptors respond to factors that
change the position of a receptor (such as
pressure, stretch, or vibration)
• Thermoreceptors respond to changes
in temperature.
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General Senses
• Include pain, pressure, touch, stretch,
and temperature
• Involve receptors widely distributed in
skin, muscles, tendons, joints, and
viscera
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Pain
• Nociceptors consist of free nerve
endings that carry impulses to the
brain.
• Receptors are abundant in skin and
mucous membranes; found in almost
every organ.
• Nociceptors use fast and slow pain
fibers.
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Pain Pathway
5
6
4
1
View animation on
“Pain pathway”
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3
2
Referred Pain
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Question
The true source of pain can be difficult to
identify because:
A. nociceptors can be stimulated by a variety
of chemicals.
B. deep body organs do not contain pain fibers.
C. some pain signals travel to the thalamus,
whereas others travel to the limbic system.
D. sensory impulses from different areas often
travel to the brain over the same pathway.
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Answer
Correct answer: D
Rationale:
• The different chemicals released by injured
receptors have nothing to do with identifying the
source of pain.
• Deep body organs contain slow pain fibers.
• Pain signals that travel to the thalamus proceed
to the postcentral gyrus, making the individual
aware of pain; signals that travel to the limbic
system trigger emotional responses to pain.
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Special Senses
• Include taste, smell, hearing, equilibrium,
and vision
• Involve receptors grouped together or
clustered in specialized organs
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Taste
Vallate
papillae
Foliate
papillae
Filiform
papillae
Fungiform
papillae
Taste buds
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Smell
4
3
2
1
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Hearing
Auricle
Auditory canal
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Middle Ear
Malleus
Incus
Stapes
Tympanic membrane
Eustachian tube
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Inner Ear
Semicircular canals
Cochlear duct
Cochlea
Vestibule
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Inner Ear (cont’d)
Basilar membrane
Organ of Corti
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Question
Which inner ear structure contains the
structures for hearing?
A.
B.
C.
D.
Vestibule
Semicircular canals
Cochlea
Auricle
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Answer
Correct answer: C
Rationale:
• The vestibule contains organs necessary
for the sense of balance.
• The semicircular canals are crucial for
balance and equilibrium.
• The auricle (pinna) is the visible part of
the external ear.
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How Hearing Occurs
2
3
1
5
View animation on “How hearing occurs”
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4
Balance
Fluid-filled
semicircular canals
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Inside the Ampulla
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Dynamic Equilibrium
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Static Equilibrium
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Question
The utricle and saccule reside
inside the:
A. vestibule.
B. ampulla.
C. organ of Corti.
D. cochlea.
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Answer
Correct answer: A
Rationale:
• The cupula resides in the ampulla.
• The cochlea contains the organ of Corti,
the hearing sense organ.
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Vision
Eyebrow
Eyelashes
Upper eyelid
Conjunctiva
Palpebral fissure
Lower eyelid
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Tarsal glands
Lacrimal Apparatus
Lacrimal gland
Lacrimal canal
Lacrimal punctum
Nasolacrimal duct
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Extrinsic Eye Muscles
Rotate eye
to slide and
downward
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Move eye up,
down,
medially, and
laterally
Tissue Layers of the Eye
Sclera
Retina
Cornea
Iris
Optic nerve
Ciliary body
Choroid
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Retina
Macula lutea
Optic disc
Fovea centralis
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Question
The outermost layer of the eye is the:
A.
B.
C.
D.
sclera.
ciliary body.
choroid.
retina.
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Answer
Correct answer: A
Rationale:
• The ciliary body and choroid are parts of
the middle vascular layer.
• The retina is part of the inner neural layer.
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Eye Chambers and Fluids
Anterior cavity
Lens
Posterior cavity
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Ciliary body
Process of Vision
1. Light focuses on the retina and
produces an upside-down image.
2. Rods and cone convert the image to
nerve impulses.
3. Impulses are transmitted to the brain.
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Refraction
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Constriction of the Pupil
Pupillary constrictor
Pupillary dilator
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Accommodation of the Lens
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Action of Photoreceptors
•
•
•
•
Rods
Concentrated at the
periphery of the retina
Active in dim light
Responsible for
night vision
Cannot distinguish
colors from each other
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•
•
•
•
Cones
Concentrated in the
center of the retina
Active in bright light
Responsible for
sharp vision
Responsible for
color vision
Transmission of Impulses
1
2
3
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Question
The bending of light rays so they focus
precisely on the retina is called:
A.
B.
C.
D.
convergence.
accommodation.
constriction.
refraction.
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Answer
Correct answer: D
Rationale:
• Convergence lines up the visual axis of
each eye.
• Accommodation occurs when the lens
changes its curvature.
• Constriction occurs when the pupil
narrows to restrict light entering the eye.
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