Chapter 9 The Senses

Chapter 9 The Senses

Chapter 9 The Senses Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 1 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 Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 2 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) Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Slide 3 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

Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 4 GENERAL SENSE ORGANS (Table 9-1) Distribution is widespread; single-cell receptors are common Examples (Figure 9-1, Table 9-1)

Free nerve endingspain, temperature, and crude touch Tactile (Meissner) corpusclesfine touch and vibration Bulbus (Ruffini) corpusclestouch and pressure Lamellar (Pacinian) corpusclespressure and

vibration Bulboid corpuscles (Krause end-bulbs)touch Golgi tendon receptorsproprioception Muscle spindlesproprioception Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 5 Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 6 Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Slide 7 SPECIAL SENSE ORGANS The eye (Figure 9-2) Layers of eyeball Scleratough outer coat; white of eye; cornea is transparent part of sclera over iris Choroidpigmented 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) Conjunctivamucous membrane covering the front surface of the sclera and also lines the eyelid; kept moist by tears found in the lacrimal gland Lenstransparent body behind the pupil; focuses light rays on the retina 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. 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

SPECIAL SENSE ORGANS (cont.) The eye (cont.) Eye fluids Aqueous humorin the anterior chamber in front of the lens Vitreous humorin the posterior chamber behind the lens

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 (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 Visual interpretation occurs in the visual cortex of the cerebrum Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 12

SPECIAL SENSE ORGANS (cont.) The ear The ear functions in hearing and in equilibrium and balancereceptors called mechanoreceptors Divisions of the ear (Figure 9-5) External ear Auricle (pinna)

External auditory canal Curving canal 2.5 cm (1 inch) in length Contains ceruminous glands Ends at the tympanic membrane Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 13 Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 14 SPECIAL SENSE ORGANS (cont.)

The ear (cont.) Divisions of the ear (cont.) Middle ear Houses ear ossiclesmalleus, 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) 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) 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.

Slide 16 Mosby items and derived items 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 17 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

sensationssweet, sour, bitter, and salty 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 Gustatory and olfactory senses work together to permit creation of many other taste sensations 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. Slide 19 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 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. Slide 21

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