Fundamentals of

Anatomy & Physiology

SIXTH EDITION

Chapter 15, part 1

Neural Integration I: Sensory Pathways and the Somatic Nervous System

PowerPoint ® Lecture Slide Presentation prepared by Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Learning Objectives

• • • Specify the components of the afferent and efferent divisions of the nervous system, and explain what is meant by the somatic nervous system.

Explain why receptors respond to specific stimuli and how the organization of a receptor affects its sensitivity.

Identify the major sensory pathways.

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Learning Objectives

• • • Explain how we can distinguish among sensations that originate in different areas of the body.

Describe the components, processes and functions of the somatic motor pathways.

Describe the levels of information processing involved in motor control.

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SECTION 15-1 An Overview of Sensory Pathways and the Somatic Nervous System

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Neural pathways

• • Afferent pathways • Sensory information coming from the sensory receptors through peripheral nerves to the spinal cord and on to the brain Efferent pathways • Motor commands coming from the brain and spinal cord, through peripheral nerves to effecter organs Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 15.1 An Overview of Neural Integration

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SECTION 15-2 Sensory Receptors and their Classification

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Sensory receptor

• • • Specialized cell or cell process that monitors specific conditions Arriving information is a sensation Awareness of a sensation is a perception Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Senses

• • General senses • Pain • Temperature • Physical distortion • Chemical detection • Receptors for general senses scattered throughout the body Special senses • Located in specific sense organs • Structurally complex Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Sensory receptors

• • Each receptor cell monitors a specific receptive field Transduction • A large enough stimulus changes the receptor potential, reaching generator potential Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Receptors

• • • Tonic receptors • Always active • Slow acting receptors Phasic receptors • Provide information about the intensity and rate of change of a stimulus • Fast acting receptors Adaptation • Reduction in sensitivity in the presence of a constant stimulus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

The general senses

• Three types of nociceptor • Provide information on pain as related to extremes of temperature • Provide information on pain as related to extremes of mechanical damage • Provide information on pain as related to extremes of dissolved chemicals • Myelinated type A fibers carry fast pain • Slower type C fibers carry slow pain Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 15.2 Receptors and Receptive Fields

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Thermoceptors and mechaniceptors

• • Found in the dermis Mechaniceptors • Sensitive to distortion of their membrane • Tactile receptors (six types) • Baroreceptors • Proprioceptors (three groups) Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 15.3 Tactile Receptors in the Skin

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Chemoreceptors

• Chemoreceptors • • Carotid bodies Aortic bodies Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 15.4 Baroreceptors and the Regulation of Visceral Function

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Figure 15.5 Chemoreceptors

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