Slide 1 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Chapter 9 The Senses

Slide 2 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. CLASSIFICATION OF SENSE ORGANS  General sense organs (Table 9-1)  Often exist as individual cells or receptor units  Widely distributed throughout the body  Special sense organs (Table 9-2)  Large and complex organs  Localized grouping of specialized receptors

Slide 3 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. CLASSIFICATION OF SENSE ORGANS (cont.)  Classification by presence or absence of covering capsule  Encapsulated  Unencapsulated (“free” or “naked”)  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)

Slide 4 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. 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 central nervous system

Slide 5 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. GENERAL SENSE ORGANS (Table 9-1)  Distribution is widespread; single-cell receptors are common  Examples (Figure 9-1, Table 9-1)  Free nerve endings—pain, temperature, and crude touch  Tactile (Meissner) corpuscles—fine touch and vibration  Bulbus (Ruffini) corpuscles—touch and pressure  Lamellar (Pacinian) corpuscles—pressure and vibration  Bulboid corpuscles (Krause end-bulbs)—touch  Golgi tendon receptors—proprioception  Muscle spindles—proprioception

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Slide 7 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Slide 8 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SPECIAL SENSE ORGANS  The eye (Figure 9-2)  Layers of eyeball Sclera—tough outer coat; “white” of eye; cornea is transparent part of sclera over iris 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; contraction of iris muscle dilates or constricts pupil 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; contraction of iris muscle dilates or constricts pupil Retina (Figure 9-4)—innermost layer of the eye; contains rods (receptors for night vision) and cones (receptors for day vision and color vision) Retina (Figure 9-4)—innermost layer of the eye; contains rods (receptors for night vision) and cones (receptors for day vision and color vision)  Conjunctiva—mucous membrane covering the front surface of the sclera and also lines the eyelid; kept moist by tears found in the lacrimal gland  Lens—transparent body behind the pupil; focuses light rays on the retina

Slide 9 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Slide 10 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Slide 11 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Slide 12 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SPECIAL SENSE ORGANS (cont.)  The eye (cont.)  Eye fluids Aqueous humor—in the anterior chamber in front of the lens Aqueous humor—in the anterior chamber in front of the lens Vitreous humor—in the posterior chamber behind the lens Vitreous humor—in the posterior chamber behind the lens  Visual pathway Innermost layer of retina contains rods and cones Innermost layer of retina contains rods and cones Impulse travels from the rods and cones through the bipolar and ganglionic layers of retina (Figure 9-4) Impulse travels from the rods and cones through the bipolar and ganglionic layers of retina (Figure 9-4) Nerve impulse leaves the eye through the optic nerve; the point of exit is free of receptors and is therefore called a blind spot 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 Visual interpretation occurs in the visual cortex of the cerebrum

Slide 13 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SPECIAL SENSE ORGANS (cont.)  The ear  The ear functions in hearing and in equilibrium and balance—receptors called mechanoreceptors  Divisions of the ear (Figure 9-5) External ear External ear  Auricle (pinna)  External auditory canal –Curving canal 2.5 cm (1 inch) in length –Contains ceruminous glands –Ends at the tympanic membrane

Slide 14 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Slide 15 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SPECIAL SENSE ORGANS (cont.)  The ear (cont.)  Divisions of the ear (cont.) Middle ear Middle ear  Houses 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 Inner ear (Figure 9-6) Inner ear (Figure 9-6)  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  Specialized hair cells on the organ of Corti respond when bent by the movement of surrounding endolymph set in motion by sound waves (Figure 9-7)

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Slide 17 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Slide 18 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SPECIAL SENSE ORGANS (cont.)  The taste receptors (Figure 9-8)  Receptors are chemoreceptors called taste buds  Cranial nerves VII and IX carry gustatory impulses  Most pathologists list four kinds of “primary” taste sensations—sweet, sour, bitter, and salty Metallic and umami (meaty) tastes are also unique and may soon be added to the list of “primary” taste sensations Metallic and umami (meaty) tastes are also unique and may soon be added to the list of “primary” taste sensations Nasal congestion interferes with stimulation of olfactory receptors and thereby dulls taste sensations Nasal congestion interferes with stimulation of olfactory receptors and thereby dulls taste sensations  Gustatory and olfactory senses work together to permit creation of many other taste sensations

Slide 19 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Slide 20 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SPECIAL SENSE ORGANS (cont.)  The smell receptors (Figure 9-9)  Receptors for fibers of olfactory or cranial nerves lie in olfactory mucosa of nasal cavity  Olfactory receptors are extremely sensitive but easily adapt (become fatigued)  Odor-causing chemicals initiate a nervous signal that is interpreted as a specific odor by the brain

Slide 21 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.