Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb PowerPoint ® Lecture Slides prepared by Vince Austin, University of Kentucky 11 Fundamentals of the Nervous System and Nervous Tissue Part A

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System  The master controlling and communicating system of the body  Functions  Sensory input – monitoring stimuli occurring inside and outside the body  Integration – interpretation of sensory input  Motor output – response to stimuli by activating effector organs

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System Figure 11.1

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Organization of the Nervous System  Central nervous system (CNS)  Brain and spinal cord  Integration and command center  Peripheral nervous system (PNS)  Paired spinal and cranial nerves  Carries messages to and from the spinal cord and brain

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Sensory (afferent) division  Sensory afferent fibers – carry impulses from skin, skeletal muscles, and joints to the brain  Visceral afferent fibers – transmit impulses from visceral organs to the brain  Motor (efferent) division  Transmits impulses from the CNS to effector organs Peripheral Nervous System (PNS): Two Functional Divisions

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Somatic nervous system  Conscious control of skeletal muscles  Autonomic nervous system (ANS)  Regulates smooth muscle, cardiac muscle, and glands  Divisions – sympathetic and parasympathetic Motor Division: Two Main Parts

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The two principal cell types of the nervous system are:  Neurons – excitable cells that transmit electrical signals  Supporting cells – cells that surround and wrap neurons Histology of Nerve Tissue

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The supporting cells (neuroglia or glial cells):  Provide a supportive scaffolding for neurons  Segregate and insulate neurons  Promote health and growth Supporting Cells: Neuroglia

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Most abundant, versatile, and highly branched glial cells  They cling to neurons and their synaptic endings, and cover capillaries  Functionally, they:  Support and brace neurons  Anchor neurons to their nutrient supplies  Guide migration of young neurons  Control the chemical environment Astrocytes

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Astrocytes Figure 11.3a

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Microglia – small, ovoid cells with spiny processes  Phagocytes that monitor the health of neurons  Ependymal cells – range in shape from squamous to columnar  They line the central cavities of the brain and spinal column Microglia and Ependymal Cells

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microglia and Ependymal Cells Figure 11.3b, c

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Oligodendrocytes – branched cells that wrap CNS nerve fibers  Schwann cells– surround fibers of the PNS  Satellite cells surround neuron cell bodies with ganglia Oligodendrocytes, Schwann Cells, and Satellite Cells

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11.3d, e Oligodendrocytes, Schwann Cells, and Satellite Cells

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Structural units of the nervous system  Composed of a body, axon, and dendrites  Long-lived, amitotic, and have a high metabolic rate  Their plasma membrane functions in:  Electrical signaling  Cell-to-cell signaling during development Neurons (Nerve Cells)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Neurons (Nerve Cells) Figure 11.4b

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Contains the nucleus and a nucleolus  Is the major biosynthetic center  Is the focal point for the outgrowth of neuronal processes  Has well-developed Nissl bodies (rough ER)  Contains an axon hillock – cone-shaped area from which axons arise Nerve Cell Body (Perikaryon or Soma)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Armlike extensions from the soma  Called tracts in the CNS and nerves in the PNS  There are two types: axons and dendrites Processes

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Short, tapering, and diffusely branched processes  They are the receptive, or input, regions of the neuron Dendrites of Motor Neurons

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Slender processes of uniform diameter arising from the hillock  Long axons are called nerve fibers  Usually there is only one unbranched axon per neuron Axons: Structure

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Generate and transmit action potentials  Secrete neurotransmitters from the axonal terminals Axons: Function

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Whitish, fatty (protein-lipoid), segmented sheath around most long axons  It functions to:  Protect the axon  Electrically insulate fibers from one another  Increase the speed of nerve impulse transmission Myelin Sheath

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Formed by Schwann cells in the PNS  A Schwann cell:  Envelopes an axon in a trough  Encloses the axon with its plasma membrane  Has concentric layers of membrane that make up the myelin sheath  Neurilemma – remaining nucleus and cytoplasm of a Schwann cell  Nodes of Ranvier: Gaps in the myelin sheath between adjacent Schwann cells Myelin Sheath and Neurilemma: Formation

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Myelin Sheath and Neurilemma: Formation Figure 11.5a-c

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Both myelinated and unmyelinated fibers are present  Myelin sheaths are formed by oligodendrocytes  Nodes of Ranvier are widely spaced Axons of the CNS

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  White matter – dense collections of myelinated fibers  Gray matter – mostly soma and unmyelinated fibers Regions of the Brain and Spinal Cord

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Structural:  Multipolar — three or more processes  Bipolar — two processes (axon and dendrite)  Unipolar — single, short process Neuron Classification

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Functional:  Sensory (afferent) — transmit impulses toward the CNS  Motor (efferent) — carry impulses away from the CNS  Interneurons (association neurons) — shuttle signals through CNS pathways Neuron Classification

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Comparison of Structural Classes of Neurons Table

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Comparison of Structural Classes of Neurons Table

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Comparison of Structural Classes of Neurons Table