Chapter 7 The Nervous System Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 7 The Nervous System Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Functions of the Nervous System 1) Sensory input – gathering information To monitor changes occurring inside and outside the body Changes = stimuli 2) Integration To process and interpret sensory input and decide if action is needed Slide 7.1a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Functions of the Nervous System 3) Motor output A response to integrated stimuli The response activates muscles or glands Slide 7.1b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Structural Classification of the Nervous System 1) Central nervous system (CNS) Brain Spinal cord 2) Peripheral nervous system (PNS) Nerve outside the brain and spinal cord Spinal nerves and cranial nerves Slide 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Functional Classification of the Peripheral Nervous System 1) Sensory (afferent) division Nerve fibers that carry information to the central nervous system Figure 7.1 Slide 7.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2) Motor (efferent) division Nerve fibers that carry impulses away from the central nervous system Two subdivisions 1) Somatic nervous system = voluntary 2) Autonomic nervous system = involuntary Figure 7.1 Slide 7.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Organization of the Nervous System Figure 7.2 Slide 7.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Nervous Tissue: Support Cells (CNS) Neuroglia – supporting cells of the CNS Astrocytes – star-shaped cells that brace and anchor neurons to capillaries Microglia – spider-like phagocytes that dispose of debris Ependymal cells – line cavities of the brain and spinal cord and have cilia that help circulate cerebrospinal fluid Oligodendrocytes – wrap their flat extensions around nerve fibers, producing myelin sheaths - Myelin sheath – fatty insulating covering Slide 7.7b

Nervous Tissue: Support Cells **Figure 7.3 p205 Slide 7.7b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Nervous Tissue: Support Cells (PNS) Schwann cells Form myelin sheath in the peripheral nervous system Figure 7.3e Slide 7.7b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Nervous Tissue: Neurons Neurons = nerve cells Cells specialized to transmit messages 2 Major regions of neurons 1) Cell body 2) Processes Slide 7.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Neuron Anatomy 1) Cell body – nucleus and metabolic center of the cell Figure 7.4a Slide 7.9b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Neuron Anatomy 2) Processes – fibers that extend from the cell body a. Dendrites – conduct impulses toward the cell body b. Axons – conduct impulses away from the cell body Figure 7.4a Slide 7.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Axons and Nerve Impulses Axons end in axonal terminals Axonal terminals contain vesicles with neurotransmitters Axonal terminals are separated from the next neuron by a gap Synaptic cleft – gap between adjacent neurons Synapse – junction between nerves Slide 7.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Nerve Fiber Coverings Schwann cells – produce myelin sheaths in jelly-roll like fashion Nodes of Ranvier – gaps in myelin sheath along the axon Figure 7.5 Slide 7.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Neuron Cell Body Location Most are found in the central nervous system (better protected) Gray matter – cell bodies and unmylenated fibers White matter – mylenated fibers Nuclei – clusters of cell bodies within the white matter of the central nervous system Ganglia – collections of cell bodies outside the central nervous system Slide 7.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings