chap10outline - Chapter 10 - Somatic and Special Senses...

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Chapter 10 - Somatic and Special Senses 10.1 Introduction (p. 262) A. Sensory receptors detect changes in the environment and stimulate neurons to send nerve impulses to the brain. B. A sensation is formed based on the sensory input. 10.2 Receptors and Sensations (p. 262) A. Each receptor is more sensitive to a specific kind of environmental change but is less sensitive to others. B. Types of Receptors (p. 262) 1. Five general types of receptors are recognized. a. Receptors sensitive to changes in chemical concentration are called chemoreceptors. b. Pain receptors detect tissue damage. c. Thermoreceptors respond to temperature differences. d. Mechanoreceptors respond to changes in pressure or movement. e. Photoreceptors in the eyes respond to light energy. C. Sensations (p. 262) 1. Sensations are feelings that occur when the brain interprets sensory impulses. 2. At the same time the sensation is being formed, the brain uses projection to send the sensation back to its point of origin so the person can pinpoint the area of stimulation. D. Sensory Adaptation (p. 262) 1. During sensory adaptation, sensory impulses are sent at decreasing rates until receptors fail to send impulses unless there is a change in strength of the stimulus. 10.3 Somatic Senses (p. 262) A. Receptors associated with the skin, muscles, joints, and viscera make up the somatic senses. B. Touch and Pressure Senses (p. 262; Fig. 10.1) 1. Three types of receptors detect touch and pressure. 2. Free ends of sensory nerve fibers in the epithelial tissues are associated with touch and pressure. 3. Meissner's corpuscles are flattened connective tissue sheaths surrounding two or more nerve fibers and are abundant in hairlese areas that are very sensitive to touch, like the lips. 4. Pacinian corpuscles are large structures of connective tissue and cells that detect deep pressure. C. Temperature Senses (p. 263) 1. Temperature receptors include two groups of free nerve endings: heat receptors and cold receptors. a. Both heat and cold receptors adapt quickly. b. Temperatures near 45 o C stimulate pain receptors; temperatures below 10 o C also stimulate pain receptors and produce a freezing sensation. D. Sense of Pain (p. 264) 1. Pain receptors consist of free nerve endings that are stimulated when tissues are damaged, and adapt little, if at all. 2. Visceral pain (Figs. 10.2-10.3) receptors are the only receptors in the viscera that produce sensations.
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a. Referred pain occurs because of the common nerve pathways leading from skin and internal organs. 3. Pain Nerve Fibers (p. 264) a. Fibers conducting pain impulses away from their source are either acute pain fibers or chronic pain fibers. b. Acute pain fibers are thin, myelinated fibers that carry impulses rapidly and cease when the stimulus stops. c.
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chap10outline - Chapter 10 - Somatic and Special Senses...

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