Download Chapter 7 Body Systems

Chapter 11
The Senses
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Lesson 11.1
Sense Organs, and the Eye
Classify sense organs as special or general and explain
the basic differences between the two groups.
2. Discuss how a stimulus is converted into a sensation.
3. Discuss the general sense organs and their functions.
4. Describe the structure of the eye and the functions of
its components.
5. Name and describe the major visual disorders.
1.
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2
General Sense Organs
 Often exist as individual cells or receptor
units
 Widely distributed throughout the body
 Different from special sense organs—
groupings of receptors within highly
complex organs
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3
Special Sense Organs
 Large and complex organs
 Localized grouping of specialized
receptors
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4
Classification of Sense Organs
 Classification by presence or absence of
covering capsule
 Encapsulated
 Unencapsulated (“free” or “naked”)
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Classification of Sense Organs
 Classification by type of stimuli required to
activate receptors
 Photoreceptors (light)
 Chemoreceptors (chemicals)
 Pain receptors (injury)
 Thermoreceptors (temperature change)
 Mechanoreceptors (movement or deforming of
capsule)
 Proprioceptors (position of body parts or changes
in muscle length or tension)
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6
Converting a Stimulus into a
Sensation
 All sense organs have common
functional characteristics
 All are able to detect a particular stimulus
 A stimulus is converted into a nerve
impulse
 A nerve impulse is perceived as a sensation
in the CNS
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7
General Sense Organs
 Distribution is widespread; single-cell receptors are
common
 Skin receptors
 Free nerve endings (several types)—pain,




discriminative touch, tickle, and temperature
Tactile (Meissner) corpuscle—fine touch and
vibration
Bulbous (Ruffini) corpuscle—touch and pressure
Lamellar (Pacini) corpuscle—pressure and vibration
Bulboid (Krause) corpuscle—touch
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8
General Sense Receptors
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9
General Sense Organs

Muscle receptors
•
•

Golgi tendon receptor—proprioception
Muscle spindle—proprioception
Deep receptors
•
•
Stretch (pressure) receptors in hollow organs
Chemical receptors—detect pH, carbon dioxide,
other chemicals
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10
External Eye Structures
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11
The Eye
 Layers of eyeball
 Sclera—tough outer coat; “white” of eye; cornea is
transparent part of sclera over iris
 Choroid—pigmented vascular layer prevents scattering of
light


Front part of this layer made of ciliary muscle and iris, the colored
part of the eye
The pupil is the hole in the center of the iris
 Retina—innermost layer of the eye; contains rods
(monochrome receptors for night vision) and cones (color
receptors for day vision)
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12
Components of the Eye
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The Eye and Vision
Function of the iris. Contraction of iris muscle dilates or constricts pupil
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The Eye & Eye Fluids
 Conjunctiva—mucous membrane covering the
front surface of the sclera and lining the eyelid
 Lens—transparent body behind the pupil;
focuses light rays on the retina
 Aqueous humor—in the anterior cavity in front
of the lens
 Vitreous humor—in the posterior cavity behind
the lens
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15
Cells of the Retina
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The Eye and Vision structures
• Fovea- a small depression
•
in the macula near the
center of the retina
• The site of acute image
formation and color
vision
Optic disc- where the optic
nerve muscles exit the eye
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Retinal (Fundus) of the Left Eye
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18
Shaken Baby Syndrome
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Courtesy Stephen Ludwig, MD. Children’s Hospital of Philadelphia. In Zitelli, Davis: Atlas
of pediatric physical diagnosis, ed 6, Mosby, 2012, St Louis.
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The Eye and Vision (cont.)
Pathway of Light Rays and Refraction
 Transparent parts of the eye that refract light

Cornea

Aqueous humor

Crystalline lens

Vitreous body
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Visual Pathway
 Innermost layer of retina contains rods and cones
 Impulse travels from the rods and cones through the
bipolar and ganglionic layers of retina
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Visual Pathway
 Nerve impulse leaves the eye through the optic nerve;
the point of exit is free of receptors and is therefore
called a blind spot
 Visual interpretation occurs in the visual cortex of the
cerebrum
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Visual Pathway
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23
Visual Disorders
 Refraction disorders
 Myopia (nearsightedness) is often caused by
elongation of the eyeball
 Hyperopia (farsightedness) is often caused by a
shortened eyeball
 Astigmatism is distortion caused by an
irregularity of the cornea or lens
 Cataracts are cloudy spots in the eye's lens
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Refraction
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25
Refraction Disorders
 Conjunctivitis (inflammation of the
conjunctiva) can interfere with refraction
 Trachoma—chronic chlamydial infection
 Acute bacterial conjunctivitis—highly
contagious infection that produces a discharge of
mucous pus
 Conjunctivitis can be caused by allergies
 Strabismus—improper alignment of eyes
 Eyes can converge (cross) or diverge
 If not corrected, can cause blindness
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Visual Disorders

Sty

Cataract
From Swartz MH: Textbook of physical diagnosis, ed 6, Philadelphia, 2010,
Saunders.
From Palay DA, Krachmer JH: Ophthalmology for the primary
care physician, St Louis, 1997, Mosby.
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27
Acute Bacterial Conjunctivitis
From Newell FW: Ophthalmology: principles and concepts, ed 8, St Louis, 1996, Mosby.
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Muscles of the Eye
 Adjust eye so the retina receives clear image
 Extrinsic muscles

Outer surface of eyeball

Voluntary

Control convergence for three-dimensional vision
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Extrinsic muscles of the eye
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Strabismus
Seidel H et al: Mosby’s guide to physical examination, ed 3, St Louis, 2002, Mosby.
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31
The Eye and Vision (cont.)
Nerve Supply to the Eye
 Sensory
 Optic nerve (CN II)
 Ophthalmic branch of trigeminal nerve (CN V)
 Motor
 Oculomotor nerve (CN III)
 Trochlear (CN IV)
 Abducens (CN VI)
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Disorders of the Retina
 Retinal detachment can be a complication of
aging, eye tumors, or head trauma
 Diabetic retinopathy—damage to retina from
hemorrhages and growth of abnormal vessels
associated with diabetes mellitus
 Glaucoma—increased intraocular pressure
decreases blood flow in retina and thus causes
retinal degeneration
 Age-related macular degeneration (AMD) —
progressive degeneration of the central part of
the retina
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33
Retinal detachment
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Retinal disorders.
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Disorders of the Retina
 Nyctalopia (night blindness) or the inability to
see in dim light is caused by retinal degeneration
or lack of vitamin A
 Color blindness—most forms inherited
 Red-green color blindness is an X-linked genetic
condition involving the inability to perceive
certain colors
 It is caused by an abnormality in the cones’
photopigments
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36
Color Vision Screening Figures
From Ishihara’s tests for colour deficiency, Tokyo, Japan, 1973, Kanehara Trading Co, Copyright
Isshinkai Foundation.
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Disorders of the Visual
Pathway
 Scotoma is the loss of only the central visual field
when only certain nerve pathways are damaged
 Cerebrovascular accidents (CVAs) can damage
visual processing centers; example is acquired
cortical color blindness
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38
Lesson 11.2
The Ear, and Taste and Smell Receptors
6. Discuss the anatomy of the ear and its sensory
function in hearing and equilibrium.
7. Name and describe the major forms of hearing
impairment.
8. Discuss the chemical receptors and their functions.
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39
The Ear
 Sense organ of hearing and also of equilibrium and
balance
 Divisions of the ear:
 External ear
 Middle ear
 Inner (internal) ear
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External Ear
 Auricle (pinna)—appendage on side of
head
 External acoustic canal



Curving tube 2.5 cm (1 inch) in length
Contains ceruminous glands
Ends at the tympanic membrane
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41
Examining the Ear
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Middle Ear
 Epithelium-lined cavity that houses the
ear ossicles—malleus, incus, and
stapes
 Ends in the oval window
 The auditory (eustachian) tube
connects the middle ear to the throat
 Inflammation called otitis media
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Acute Otitis Media
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The Ear
From Kliegman RM, Behrman RE, Jenson HB, Stanton BF: Nelson textbook of pediatrics, ed 18,
Philadelphia, 2007, Saunders.
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45
Inner Ear
 Bony labyrinth filled with perilymph
 Subdivided into the vestibule, semicircular
canals, and cochlea
 Membranous labyrinth filled with endolymph
 The receptors for balance in the semicircular
canals are called cristae ampullaris
 Sensory hair cells on the organ of Corti (spiral
organ) respond when bent by the movement of
surrounding endolymph set in motion by sound
waves
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46
The Inner Ear
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47
Effect of Sound Waves on
Cochlear Structures
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Effect of Sound Waves on
Cochlear Structures
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Equilibrium
 Ciliated equilibrium sensory receptors are located in
vestibule and semicircular canals.
 Types of receptors
 Maculae
 Cristae
 Nerve supply via vestibular nerve
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The Ear Action of the vestibular equilibrium
receptors (maculae).
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The Ear Action of the equilibrium receptors
(cristae) in the semicircular canals.
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Hearing Disorders
 Conduction impairments
 Can be caused by blockage of the external or middle
ear (for example, by cerumen and tumors)
 Otosclerosis—inherited bone disorder involving
irregularity of the stapes; it first appears as tinnitus
(ringing) then progresses to hearing loss
 Otitis—ear inflammation caused by infection; can
produce swelling and fluids that block sound
conduction
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53
Nerve Impairment
 Presbycusis—progressive nerve deafness
associated with aging
 Progressive nerve deafness can also result from
chronic exposure to loud noise
 Ménière disease—chronic inner ear disorder
characterized by tinnitus, nerve deafness, and
vertigo
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54
The Taste Receptors
 Receptors are chemoreceptors called taste buds
 Cranial nerves VII and IX carry gustatory impulses
 Only four kinds of taste sensations—sweet, sour,
bitter, salty
 Gustatory and olfactory senses work together
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The Tongue
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The Smell Receptors
 Receptors for fibers of olfactory (cranial nerve I) lie
in olfactory mucosa of nasal cavity
 Olfactory receptors are extremely sensitive but
easily fatigued
 Odor-causing chemicals initiate a nervous signal
that is interpreted as a specific odor by the brain
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Olfactory Structures
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