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Ch.13The Peripheral Nervous System

Ch.13The Peripheral Nervous System - Ch.13 The Peripheral...

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Ch.13: The Peripheral Nervous System (PNS) and Reflex Activity Shreya Buch Peripheral Nervous System (PNS) (fig.13.1) PNS all neural structures outside the brain and spinal cord Includes sensory receptors, peripheral nerves, associated ganglia, and motor endings Provides links to and from the external environment Part 1- Sensory Receptors and Sensation Sensory Receptors Structures specialized to respond to stimuli Activation of sensory receptors results in depolarization that trigger impulses along the afferent PNS fibers coursing to the CNS The realization of these stimuli, sensation (awareness of stimulus) and perception (interpretation of the meaning of the stimulus), occur in the brain Sensory receptors are classified by: (1) By the type of stimulus they detect (2) By their body location ,and (3) By their structural complexity (1 ) Receptor Classification by Stimulus Type Mechanoreceptors respond to touch, pressure, vibration, stretch, and itch-receptors generate impulse when they or surrounding tissue are deformed by a mechanical force Thermoreceptors sensitive to changes in temperature Photoreceptors respond to light energy (e.g., retina) Chemoreceptors respond to chemicals in fluid (e.g., smell, taste, changes in blood chemistry) Nociceptors sensitive to pain-causing stimuli-respond to potentially damaging stimuli that result in pain (e.g., extreme heat, extreme cold, excessive pressure) (2) Receptor Class by Location: a) Exteroceptors Respond to stimuli arising outside the body Found near the body surface Sensitive to touch, pressure, pain, and temperature Include the special sense organs (vision, hearing, taste, equilibrium) b) Interoceptors Respond to stimuli arising within the body-also called
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