Anatomy and Physiology I The Nervous System Basic Structure and Function Instructor: Mary Holman

Three Basic Functions of the Nervous System Sensory Function Sensory or afferent neurons Integrative Function Interneurons Motor Function Motor or efferent neurons

Fig. 10.2a Brain Spinal cord Spinal nerves (31 pairs) Cranial nerves (12 pairs) CNS vs PNS Central Nervous System Peripheral Nervous System

Divisions of the Nervous System Central Nervous System CNS Brain Spinal Cord Peripheral Nervous System PNS Cranial Nerves Spinal Nerves Ganglia Sensory Receptors

Divisions of the PNS Somatic Nervous System Sensory neurons Motor neurons to skeletal muscle only Autonomic Nervous System Autonomic sensory neurons - visceral Motor neuron impulses to smooth & cardiac muscle, glands and adipose tissue Sympathetic vs. Parasympathetic Motor Divisions Enteric Nervous System Enteric complexes of the gut

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central nervous systemPeripheral nervous system Cell body Interneurons Dendrites Axon Sensory (afferent) neuron Motor (efferent) neuron Cell body Axon (central process) Axon (peripheral process) Sensory receptor Effector (muscle or gland) Axon terminal

Cells of Neural Tissue Neurons The electrically excitable nerve cells responsible for the functions of the nervous system Neuroglia (glia, neuroglia, glial) Support, nourish, & protect neurons

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrites Cell body Axon Nuclei of neuroglia © Ed Reschke The Neuron 600x

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell body Neurofibrils Nucleus Nucleolus Dendrites Impulse Nodes of Ranvier Myelin (cut) Axon Chromatophilic substance ( Nissl bodies) Axonal hillock Portion of a collateral Schwann cell Nucleus of Schwann cell Synaptic knob of axon terminal Neuron with Myelinated Axon

Fig Dendrites Axon Direction of impulse (a) Multipolar Central process Peripheral process (c) Unipolar(b) Bipolar (eyes,nose,ears)

Neuroglia of the PNS Schwann Cells Produce myelin sheath Satellite Cells Support neuronal clusters in ganglia

Fig. 10.4a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrite Node of Ranvier Myelinated region of axon Axon Unmyelinated region of axon Neuron cell body Neuron nucleus Medullated or Myelinated Axon Schwann cells Neurolemma containing nucleus

Fig. 10.4b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neurilemma Myelin sheath Neurofibrils Axon Node of Ranvier Myelin Schwann cell nucleus © Biophoto Associates/Photo Researchers, Inc. 650x Schwann Cell

Fig. 10.4c Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Enveloping Schwann cell Schwann cell nucleus Unmyelinated axon Longitudinal groove Schwann Cell with non-myelinated Axons Axon

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Schwann cell cytoplasm Myelin sheath Myelinated axon Unmyelinated axon © Dennis Emery 30,000x

Neuroglia of the CNS Astrocytes major support cells provide nutrients, monitor metabolism etc Oligodendrocytes myelinate axons in CNS Microglia phagocytic Ependymal line ventricles & central canal produce cerebrospinal fluid (CSF)

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Microglial cell Axon Oligodendrocyte Astrocyte Capillary Neuron Myelin sheath (cut) Node of Ranvier Ependymal cell Fluid-filled cavity of the brain or spinal cord Neuroglia of CNS

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neuroglia Neuron cell body Tissues and Organs: A Text-Atlas of Scanning Electron Microscopy, by R.G. Kessel and R.H. Kardon. ©1979 W.H. Freeman and Company SEM 10,000x

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Axon Site of injury Schwann cells (a) (b) (c) (d) (e) Changes over time Motor neuron cell body Former connection reestablished Schwann cells Form new myelin sheath Schwann cell tube extends distal to injury Proximal end of injured axon regenerates into tube of Schwann cells Distal portion of axon degenerates Skeletal muscle fiber Axonal Repair