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C HAPTER 10. AFTER YOU HAVE COMPLETED THIS CHAPTER, YOU SHOULD BE ABLE TO: 1. Classify sense organs as special or general and explain tne basic differences.

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Presentation on theme: "C HAPTER 10. AFTER YOU HAVE COMPLETED THIS CHAPTER, YOU SHOULD BE ABLE TO: 1. Classify sense organs as special or general and explain tne basic differences."— Presentation transcript:

1 C HAPTER 10

2 AFTER YOU HAVE COMPLETED THIS CHAPTER, YOU SHOULD BE ABLE TO: 1. Classify sense organs as special or general and explain tne 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. List the major senses. 5. Describe the structure of the sys and the functions of its components. 6. Name and describe the major visual disorders. 7. Discuss the anatomy of the ear and its sensory function in nearing and equilibrium. 8. Name and describe the major forms of nearing impairment. 9. Discuss the chemical receptors and their functions.

3 In this presentation we will discuss the following: A.CLASSIFICATION OF SENSE ORGANS B.CONVERTING A STIMULUS INTO A SENSATION C.GENERAL SENSE ORGANS D.SPECIAL SENSE ORGANS  The Eye  Visual Disorders  The Ear  Hearing Disorders  The Taste Receptors  The Smell Receptors A.CLASSIFICATION OF SENSE ORGANS B.CONVERTING A STIMULUS INTO A SENSATION C.GENERAL SENSE ORGANS D.SPECIAL SENSE ORGANS  The Eye  Visual Disorders  The Ear  Hearing Disorders  The Taste Receptors  The Smell Receptors

4 CLASSIFICATION OF THE SENSE ORGANS A.General sense organs (Table 10-1) 1. Often exist as individual cells or receptor units 2. Widely distributed throughout the body Page(s)

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8 B.Special Sense Organs (Table 10-2) 1. Large and complex organs 2. Localized grouping of specialized receptors CLASSIFICATION OF THE SENSE ORGANS Page(s)

9 C.Classification by presence or absence of covering capsule CLASSIFICATION OF THE SENSE ORGANS 1. Encapsulated 2. Unencapsulated (“free” or “naked”) Page(s) 312, 315

10 D.Classification by type of stimuli required to activated receptors 1. Photoreceptors (light) 2. Chemoreceptors (chemicals) 3. Pain receptors (injury) 4. Thermoreceptors (temperature change) 5. Mechanoreceptors (movement or deforming of capsule) 6. Proprioceptors (position of body parts or changes in muscle length or tension) CLASSIFICATION OF THE SENSE ORGANS Page(s) 312

11 CONVERTING A STIMULUS INTO A SENSATION A.All sense organs have common functional characteristics 1. All are able to detect a particular stimulus 2. A stimulus is converted into a nerve impulse 3. A nerve impulse is perceived as a sensation in the CNS Page(s) 314

12 GENERAL SENSE ORGANS (T ABLE 10-1) A.Distribution is widespread; Single-celled receptors are common Page(s) 314

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15 1. Free nerve endings—pain, crude touch, and temperature 2. Meissner’s corpuscles—fine touch and vibration 3. Ruffini’s corpuscles—touch and pressure 4. Pacinian corpuscles— pressure and vibration GENERAL SENSE ORGANS (T ABLE 10-1) Page(s) B.Examples (Figure 10-1, Table 10-1)

16 5. Krause’s End bulbs—touch 6. Golgi tendon receptors— proprioception 7. Muscle spindles— proprioception GENERAL SENSE ORGANS (T ABLE 10-1) A.Examples (Figure 10-1, Table 10-1) Page(s)

17 A.The Eye (Figure 10-2, 10-3) 1. Layers of eyeball a.Sclera—tough outer coat; “white” of eye; cornea is transparent part of sclera over iris SPECIAL SENSE ORGANS Page(s)

18 b.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; pupil is the hole in the center of the iris; contraction of iris muscle dilates or constricts pupil SPECIAL SENSE ORGANS A.The Eye 1. Layers of eyeball Page(s)

19 A.The Eye 1. Layers of eyeball b.Retina—innermost layer of the eye; contains rods (receptors for night vision) and cones (receptors for day vision and color vision) (Figure 10-5) SPECIAL SENSE ORGANS Page(s)

20 b.Retina— innermost layer of the eye; contains rods (receptors for night vision) and cones (receptors for day vision and color vision) (Figure 10-5) SPECIAL SENSE ORGANS A.The Eye 1. Layers of eyeball Page(s)

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22 2. Conjunctiva— mucous membrane covering the front surface of the sclera and lining the eyelids 3. Lens— transparent body behind the pupil; focuses light rays on the retina SPECIAL SENSE ORGANS A.The Eye Page(s)

23 4. Eye fluids a.Aqueous humor—in the anterior cavity in front of the lens b.Vitreous humor—in the posterior cavity behind the lens SPECIAL SENSE ORGANS A.The Eye Page(s)

24 A.The Eye 5. Visual Pathway a.Innermost layer of retina contains rods and cones b.Impulse travels from the rods and cones through the bipolar and ganglionic layers of retina (Figure 10-5) SPECIAL SENSE ORGANS Page(s)

25 A.The Eye 5. Visual Pathway c.Nerve impulse leaves the eye through the optic nerve; the point of exit is free of receptors and is therefore called a blind spot d.Visual interpretation occurs in the visual cortex of the cerebrum SPECIAL SENSE ORGANS Page(s)

26 SPECIAL SENSE ORGANS B.Visual Disorders 1. Refraction Disorders (Figure 10-7) a.Myopia(nearsightedness) is often caused by elongation of the eyeball b.Hyperopia (farsightedness) is often caused by a shortened eyeball c.Astigmatism is distortion caused by an irregularity of the cornea or lens Page(s)

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28 B.Visual Disorders d. Conjunctivitis (inflammation of the conjunctiva) can interfere with refraction 1)Trachoma—chronic chlamydial infection 2)Acute bacterial conjunctivitis— highly contagious infection that produces a discharge of mucous pus (Figure 10-8) 3)Conjunctivitis can be caused by allergies SPECIAL SENSE ORGANS Page(s) 322

29 B.Visual Disorders e. Strabismus— improper alignment of eyes (Figure 10-8) 1)Eyes can converge (cross) or diverge 2)If not corrected, can cause blindness SPECIAL SENSE ORGANS Page(s) 322

30 SPECIAL SENSE ORGANS B.Visual Disorders 2. Disorders of the retina a)Retinal Detachment can be a complication of aging, eye tumors, or head trauma b)Diabetic retinopathy—damage to retina from hemorrhages and growth of abnormal vessels associated with diabetes mellitus c)Glaucoma—increased intraocular pressure—decreases blood flow in retina and thus causes retinal degenereation Page(s)

31 SPECIAL SENSE ORGANS B.Visual Disorders d)Nyctalopia (night blindness) or inability to see in dim light is caused by retinal degeneration or lack of vitamin A e)Macular degeneration—progressive degeneration of central part of retina; leading cause of permanent blindness in elderly f)Red-green colorblindness is an X-linked genetic condition in which certain colors are not seen properly; It is caused by an abnormality in the cones’ photopigments Page(s)

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33 SPECIAL SENSE ORGANS B.Visual Disorders 3. Disorders of the visual pathway a)Degeneration of the optic nerve resulting from diabetes, glaucoma, and other causes can impair vision b)Scotoma is the loss of only the central visual field when only certain nerve pathways are damaged c)Cerebrovascular accidents (CVAs) can damage visual processing centers; example is acquired cortical color blindness Page(s)

34 C.The Ear 1. The ear functions in hearing and in equilibrium and balance a.Receptors for hearing and equilibrium are mechanoreceptors SPECIAL SENSE ORGANS Page(s) 326

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36 SPECIAL SENSE ORGANS C.The Ear 2. Divisions of the ear (Figure 10-12) a.External ear 1)Auricle (pinna) 2)External auditory canal a)Curving canal 2.5 cm (1 inch) in length b)Contains ceruminous glands c)Ends at the tympanic membrane Page(s)

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38 SPECIAL SENSE ORGANS C.The Ear 2. Divisions of the ear b.Middle ear 1)Houses ear ossicles—Malleus, incus, and stapes (hammer, anvil, and stirrup) 2)Ends in the oval window 3)The auditory (eustachian) tube connects the middle ear to the throat 4)Inflammation called otitis media Page(s)

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40 SPECIAL SENSE ORGANS C.The Ear 2. Divisions of the ear c.Inner ear (Figure 10-13) 1)Bony labyrinth filled with perilymph 2)Subdivided into the vestible, semicircular canals, and cochlea 3)Membranous labyrinth filled with endolymph Page(s)

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42 SPECIAL SENSE ORGANS C.The Ear 4) The receptors for balance in the semicircular canals are called crista ampullaris 5) Specialized hair cells on the organ of Corti respond when bent by the movement of surrounding endolymph set in motion by sound waives (Figure ) Page(s)

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44 SPECIAL SENSE ORGANS D.Hearing Disorders 1. Conductions Impairments a.Can be caused by blockage of the external or middle ear (for example, cerumen and tumors) b.Otoschlerosis—inherited bone disorder involving irregularity of the stapes; it first appears as tinnitus (ringing) then progresses to hearing loss c.Otitis—ear inflammation caused by infection; can produce swelling and fluids that block sound conduction Page(s)

45 SPECIAL SENSE ORGANS D.Hearing Disorders 2. Nerve impairment a.Presbycusis—progressive nerve deafness associated with aging b.Progressive nerve deafness also can result from chroinic exposure to loud noise c.Meniere’s disease—chroinic inner ear disorder characterized by tinnitus, nerve deafness, and vertigo Page(s) 332

46 SPECIAL SENSE ORGANS E.The taste receptors (Figure 10-15) 1. Receptors are chemoreceptors called taste buds 2. Cranial nerves VII and IX carry gustatory impulses 3. Most physiologists list only four kinds of primary taste sensations—sweet, sour, bitter, salty (umami and metallic tastes are sometimes included as primary taste sensations) 4. Gustatory and olfactory senses work together Page(s) 332

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48 SPECIAL SENSE ORGANS F.The smell receptors (Figure 10-16) 1. Receptors for fibers of olfactory (cranial nerve I) lie in olfactory mucosa of nasal cavity 2. Olfactory receptors are extremely sensitive but easily fatigued 3. Odor-causing chemicals initiate a nerveous signal that is interpreted as a specific odor by the brain Page(s)

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50 C REDITS A.All photos and references are taken from: Thibodeau, Gary, & Patton, Kevin. (2005). The Human body in health & disease. Mosby. ISBN: A.All photos and references are taken from: Thibodeau, Gary, & Patton, Kevin. (2005). The Human body in health & disease. Mosby. ISBN:


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