PERIPHERAL NERVOUS SYSTEM

PERIPHERAL NERVOUS SYSTEM - including chemical, stretching,...

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PERIPHERAL NERVOUS SYSTEM The PNS provides links from and to the external environment. Its nerve fibers connect virtually every part of the body, enabling the CNS to receive information and to carry out its decisions. The PNS includes: all neural structures outside the brain and spinal cord. It includes sensory receptors, peripheral nerves and their associated ganglia, and efferent motor endings. Sensory receptors are modified dendrites -- specialized structures that respond to changes in the environment known as stimuli. Activation of a sensory receptor triggers impulses along the afferent fibers coursing to the brain. Classification of Sensory Receptors: 1. location in the body 2. type of stimulus detected 3. relative complexity of their structure Location: Three classes recognized: 1. Exteroceptors - sensitive to stimuli arising outside the body. Receptors located at or near the body surface. Include touch, pressure, pain, and temperature, and most special sense organs. 2. Interoceptors - respond to stimuli arising from within the body. Excited by a variety of stimuli,
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Unformatted text preview: including chemical, stretching, and temperature. Activation may cause the feeling of pain, discomfort, hunger, thirst. 3. Proprioceptors special category that responds to internal stimuli; however, their location is restricted to the musculoskeletal system. ccur in skeletal muscles, tendons, joints, and ligaments. Constantly advise the brain on body movements. Stimulus Detected: 1. Mechanoreceptors - touch, pressure, vibrations, stretch. 2. Thermoreceptors - sensitive to temperature changes. 3. Photoreceptors - retina of the eye. 4. Chemoreceptors- respond to chemicals in solution, molecules smelled or tasted, changes in blood chemistry. 5. Nociceptors - respond to potentially damaging stimuli that result in pain. Virtually all receptors function as nociceptors at one time or another. (Excessive heat, cold, pressure and chemicals released at site of inflammation)...
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