Essentials of Anatomy & Physiology, 4th Edition Martini / Bartholomew The Nervous System PowerPoint® Lecture Outlines prepared by Alan Magid, Duke University Slides 1 to 145 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Nervous System Two Organ Systems Control All the Other Organ Systems • Nervous system characteristics • Rapid response • Brief duration • Endocrine system characteristics • Slower response • Long duration Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Nervous System Two Anatomical Divisions • Central nervous system (CNS) •Brain • Spinal cord • Peripheral nervous system (PNS) • All the neural tissue outside CNS • Afferent division (sensory input) • Efferent division (motor output) • Somatic nervous system • Autonomic nervous system Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information Motor commands NERVOUS SYSTEM within within afferent division efferent division includes Somatic Autonomic nervous nervous system system Parasympathetic Sympathetic division division Receptors Effectors Smooth muscle Somatic sensory Visceral sensory Skeletal Cardiac receptors (monitor receptors (monitor muscle the outside world internal conditions muscle and our position and the status Glands in it) of other organ systems) Adipose tissue Figure 8-1 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 1 of 7 PERIPHERAL NERVOUS SYSTEM Receptors Somatic sensory Visceral sensory receptors (monitor receptors (monitor the outside world internal conditions and our position and the status in it) of other organ systems) Figure 8-1 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 2 of 7 PERIPHERAL Sensory information NERVOUS SYSTEM within afferent division Receptors Somatic sensory Visceral sensory receptors (monitor receptors (monitor the outside world internal conditions and our position and the status in it) of other organ systems) Figure 8-1 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 3 of 7 CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information NERVOUS SYSTEM within afferent division Receptors Somatic sensory Visceral sensory receptors (monitor receptors (monitor the outside world internal conditions and our position and the status in it) of other organ systems) Figure 8-1 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 4 of 7 CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information Motor commands NERVOUS SYSTEM within within afferent division efferent division Receptors Somatic sensory Visceral sensory receptors (monitor receptors (monitor the outside world internal conditions and our position and the status in it) of other organ systems) Figure 8-1 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 5 of 7 CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information Motor commands NERVOUS SYSTEM within within afferent division efferent division includes Somatic nervous system Receptors Effectors Somatic sensory Visceral sensory Skeletal receptors (monitor receptors (monitor muscle the outside world internal conditions and our position and the status in it) of other organ systems) Figure 8-1 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 6 of 7 CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information Motor commands NERVOUS SYSTEM within within afferent division efferent division includes Somatic Autonomic nervous nervous system system Parasympathetic Sympathetic division division Receptors Effectors Smooth muscle Somatic sensory Visceral sensory Skeletal Cardiac receptors (monitor receptors (monitor muscle the outside world internal conditions muscle and our position and the status Glands in it) of other organ systems) Adipose tissue Figure 8-1 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 7 of 7 Neural Tissue Organization Two Classes of Neural Cells • Neurons • For information transfer, processing, and storage • Neuroglia • Supporting framework for neurons • Phagocytes Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neural Tissue Organization Three Classes of Neurons • Sensory neurons • Deliver information to CNS • Motor neurons • Stimulate or inhibit peripheral tissues • Interneurons (association neurons) • Located between sensory and motor neurons • Analyze inputs, coordinate outputs Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neural Tissue Organization Neuron Anatomy • Cell body • Nucleus • Mitochondria, RER, other organelles • Dendrites • Several branches • Signal reception (inward) • Axon • Signal propagation (outward) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neural Tissue Organization The Anatomy of a Representative Neuron Figure 8-2 Neural Tissue Organization Structural Classes of Neurons • Unipolar • Dendrite, axon continuous • Afferent neurons • Multipolar • Many dendrites, one axon • Most common class of neuron • Bipolar • One dendrite, one axon • Very rare Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Function A Structural Classification of Neurons Figure 8-3 Neural Tissue Organization Key Note Neurons perform all of the communication, information processing, and control functions of the nervous system. Neuroglia outnumber neurons and have functions essential to preserving the physical and biochemical structure of neural tissue and the survival of neurons. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neural Tissue Organization Anatomic Organization of CNS Neurons • Center—Collection of neurons with a shared function • Nucleus—A center with a discrete anatomical boundary • Neural cortex—Gray matter covering of brain portions • White matter—Bundles of axons (tracts) that share origins, destinations, and functions Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neural Tissue Organization Anatomic Organization of PNS Neurons • Ganglia—Groupings of neuron cell bodies • Nerve—Bundle of axons supported by connective tissue • Spinal nerves • To/from spinal cord • Cranial nerves • To/from brain Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neural Tissue Organization The Anatomical Organization of the Nervous System Figure 8-6 Neural Tissue Organization Pathways in the CNS • Ascending pathways Carry information from sensory receptors to processing centers in the brain • Descending pathways Carry commands from specialized CNS centers to skeletal muscles Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Function The Membrane Potential • Resting potential • Excess negative charge inside the neuron • Created and maintained by Na-K ion pump • Negative voltage (potential) inside • -70 mV (0.07 Volts) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Function The Cell Membrane at the Resting Potential Figure 8-7 Neuron Function Changes in Membrane Potential • Result from changes in ion movement • Ions move in transmembrane channels • Membrane channels can open or close • If Na+ channels open positive charges enter cell membrane potential moves positive (depolarization) • If K+ channels open positive charges leave cell membrane potential moves negative (hyperpolarization) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Function Key Note A membrane potential exists across the cell membrane because (1) the cytosol and the extracellular fluid differ in their ionic composition, and (2) the cell membrane is selectively permeable to these ions. The membrane potential can quickly change, as the ionic permeability of the cell membrane changes, in response to chemical or physical stimuli. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Function Generation of Action Potential • Depolarization of membrane to threshold • Rapid opening of voltage-gated Na+ channels • Na+ entry causes rapid depolarization • Voltage-gated K+ channels open • K+ exit causes rapid repolarization • Refractory period ends as membrane recovers the resting state Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Activation of voltage- Depolarization to threshold regulated sodium channels and rapid depolarization Sodium ions Local current Potassium ions Inactivation of sodium channels and activation of voltage-regulated potassium channels +30 DEPOLARIZATION REPOLARIZATION 3 0 2 The return to normal Threshold _60 permeability and resting state _70 1 4 Transmembrane(mV) potential Resting potential REFRACTORY PERIOD 0123 Time (msec) Figure 8-8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 1 of 5 Depolarization to threshold Sodium ions Local current +30 DEPOLARIZATION 0 Threshold _60 _70 1 Transmembrane(mV) potential Resting potential 0123 Time (msec) Figure 8-8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 2 of 5 Activation of voltage- Depolarization to threshold regulated sodium channels and rapid depolarization Sodium ions Local current Potassium ions +30 DEPOLARIZATION 0 2 Threshold _60 _70 1 Transmembrane(mV) potential Resting potential 0123 Time (msec) Figure 8-8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 3 of 5 Activation