Lecture Human anatomy and physiology - Chapter 13: The peripheral nervous system and reflex activity (part a)

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In this chapter, you will learn to: Define peripheral nervous system and list its components; classify general sensory receptors by structure, stimulus detected, and body location; outline the events that lead to sensation and perception; describe receptor and generator potentials and sensory adaptation; describe the main aspects of sensory perception.

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Nội dung Text: Lecture Human anatomy and physiology - Chapter 13: The peripheral nervous system and reflex activity (part a)

PowerPoint® Lecture Slides prepared by Janice Meeking, Mount Royal College CHAPTER 13 The Peripheral Nervous System and Reflex Activity: Part A Copyright © 2010 Pearson Education, Inc.
Peripheral Nervous System (PNS) • All neural structures outside the brain • Sensory receptors • Peripheral nerves and associated ganglia • Motor endings Copyright © 2010 Pearson Education, Inc.
Central nervous system (CNS) Peripheral nervous system (PNS) Sensory (afferent) Motor (efferent) division division Somatic nervous Autonomic nervous system system (ANS) Sympathetic Parasympathetic division division Copyright © 2010 Pearson Education, Inc. Figure 13.1
Sensory Receptors • Specialized to respond to changes in their environment (stimuli) • Activation results in graded potentials that trigger nerve impulses • Sensation (awareness of stimulus) and perception (interpretation of the meaning of the stimulus) occur in the brain Copyright © 2010 Pearson Education, Inc.
Classification of Receptors • Based on: • Stimulus type • Location • Structural complexity Copyright © 2010 Pearson Education, Inc.
Classification by Stimulus Type • Mechanoreceptors—respond to touch, pressure, vibration, stretch, and itch • Thermoreceptors—sensitive to changes in temperature • Photoreceptors—respond to light energy (e.g., retina) • Chemoreceptors—respond to chemicals (e.g., smell, taste, changes in blood chemistry) • Nociceptors—sensitive to pain-causing stimuli (e.g. extreme heat or cold, excessive pressure, inflammatory chemicals) Copyright © 2010 Pearson Education, Inc.
Classification by Location 1. Exteroceptors • Respond to stimuli arising outside the body • Receptors in the skin for touch, pressure, pain, and temperature • Most special sense organs Copyright © 2010 Pearson Education, Inc.
Classification by Location 2. Interoceptors (visceroceptors) • Respond to stimuli arising in internal viscera and blood vessels • Sensitive to chemical changes, tissue stretch, and temperature changes Copyright © 2010 Pearson Education, Inc.
Classification by Location 3. Proprioceptors • Respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles • Inform the brain of one’s movements Copyright © 2010 Pearson Education, Inc.
Classification by Structural Complexity 1. Complex receptors (special sense organs) • Vision, hearing, equilibrium, smell, and taste (Chapter 15) 2. Simple receptors for general senses: • Tactile sensations (touch, pressure, stretch, vibration), temperature, pain, and muscle sense • Unencapsulated (free) or encapsulated dendritic endings Copyright © 2010 Pearson Education, Inc.
Unencapsulated Dendritic Endings • Thermoreceptors • Cold receptors (10–40ºC); in superficial dermis • Heat receptors (32–48ºC); in deeper dermis Copyright © 2010 Pearson Education, Inc.
Unencapsulated Dendritic Endings • Nociceptors • Respond to: • Pinching • Chemicals from damaged tissue • Temperatures outside the range of thermoreceptors • Capsaicin Copyright © 2010 Pearson Education, Inc.
Unencapsulated Dendritic Endings • Light touch receptors • Tactile (Merkel) discs • Hair follicle receptors Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc. Table 13.1
Encapsulated Dendritic Endings • All are mechanoreceptors • Meissner’s (tactile) corpuscles—discriminative touch • Pacinian (lamellated) corpuscles—deep pressure and vibration • Ruffini endings—deep continuous pressure • Muscle spindles—muscle stretch • Golgi tendon organs—stretch in tendons • Joint kinesthetic receptors—stretch in articular capsules Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc. Table 13.1
From Sensation to Perception • Survival depends upon sensation and perception • Sensation: the awareness of changes in the internal and external environment • Perception: the conscious interpretation of those stimuli Copyright © 2010 Pearson Education, Inc.
Sensory Integration • Input comes from exteroceptors, proprioceptors, and interoceptors • Input is relayed toward the head, but is processed along the way Copyright © 2010 Pearson Education, Inc.
Sensory Integration • Levels of neural integration in sensory systems: 1. Receptor level—the sensor receptors 2. Circuit level—ascending pathways 3. Perceptual level—neuronal circuits in the cerebral cortex Copyright © 2010 Pearson Education, Inc.
3 Perceptual level (processing in cortical sensory centers) Motor cortex Somatosensory cortex Thalamus Reticular formation Pons Cerebellum 2 Circuit level Medulla (processing in Spinal ascending pathways) cord Free nerve endings (pain, cold, warmth) Muscle spindle 1 Receptor level (sensory reception Joint and transmission kinesthetic to CNS) receptor Copyright © 2010 Pearson Education, Inc. Figure 13.2