The Nervous System

1 Essentials of Human Anatomy & PhysiologySeventh EditionElaine N. MariebChapter 7 The Nervous SystemCopyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsSlides Nervous SystemLecture Slides in PowerPoint by Jerry L. CookFunctions of the Nervous SystemFunctions of the Nervous System Sensory input gathering information To monitor changes occurring inside and outsidethe body Changes = stimuli IntegrationSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummings Integration To process and interpret sensory input and decideif action is needed Motor output A response to integrated stimuli The response activates muscles or glandsStructural Classification of the NervousStructural Classification of the NervousSystemSystem Central Nervous System (CNS) Brain and Spinal cord Acts as integrating and command center interpretincoming sensory information and issue instructionsSlide 2003 Pearson Education, Inc.

2 Publishing as Benjamin Cummingsincoming sensory information and issue instructionsbased on past experiences and current conditions Peripheral Nervous System (PNS) Nerves outside the brain and spinal cord Link all parts of the body by carrying impulses to theCNS and backFunctional Classification of theFunctional Classification of thePeripheral Nervous SystemPeripheral Nervous System Sensory (afferent) division Nerve fibers that carry informationtothecentral Nervous systemSlide 2003 Pearson Education, Inc. publishing as Benjamin CummingsFigure Classification of theFunctional Classification of thePeripheral Nervous SystemPeripheral Nervous System Motor (efferent) division Nerve fibers that carry impulsesaway fromthe central Nervous systemSlide 2003 Pearson Education, Inc.

3 Publishing as Benjamin CummingsFigure Classification of theFunctional Classification of thePeripheral Nervous SystemPeripheral Nervous System Motor (efferent) division Two subdivisions Somatic Nervous System = voluntarynervous systemSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummingsnervous System Skeletal muscle reflexes such as stretchreflex are initiated involuntarily by samefibers Autonomic Nervous System = involuntarynervous System Sympathetic and parasympatheticdivisionsOrganization of the Nervous SystemOrganization of the Nervous SystemSlide 2003 Pearson Education, Inc. publishing as Benjamin CummingsFigure Tissue: Support CellsNervous Tissue: Support Cells(Neuroglia)(Neuroglia) -- gliaglia Astrocytes Abundant, star-shaped cells Brace neurons Form barrierSlide 2003 Pearson Education, Inc.

4 Publishing as Benjamin Cummings Form barrierbetween capillariesand neurons and makeexchanges betweenthe two Control the chemicalenvironment ofthe brain by capturing ions andneurotransmittersFigure Tissue: Support CellsNervous Tissue: Support Cells Microglia Spider-like phagocytes Dispose of debris dead cells and bacteriaSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ependymal cells Line cavities of thebrain and spinal cord Circulatecerebrospinalfluid with ciliaFigure , cNervous Tissue: Support CellsNervous Tissue: Support Cells Oligodendrocytes Wrap their flatextensions tightlyaround the nerveSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummingsaround the nervefibers Produce myelinsheath around nervefibers in the centralnervous systemFigure Tissue: Support CellsNervous Tissue: Support Cells Satellite cells Protect neuron cell bodies Schwann cells Form myelin sheath in the peripheral nervoussystemSlide 2003 Pearson Education, Inc.

5 Publishing as Benjamin CummingsFigure Neuroglia are not able to transmit nerve impulses butdo not lose their ability to divide, unlike neuronsNervous Tissue: NeuronsNervous Tissue: Neurons Neurons = nerve cells Cells specialized to transmit messages Major regions of neuronsSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummings Major regions of neurons Cell body nucleus and metabolic centerof the cell Processes fibers that extend from thecell bodyNeuron AnatomyNeuron Anatomy Cell body Nisslsubstance specializedroughSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummingsroughendoplasmicreticulum Neurofibrils intermediatecytoskeletonthat maintainscell shapeFigure AnatomyNeuron Anatomy Cell body NucleusSlide 2003 Pearson Education, Inc.

6 Publishing as Benjamin Cummings Nucleus LargenucleolusFigure AnatomyNeuron Anatomy Extensionsoutside the cellbody Dendrites conductSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummingsconductimpulses towardthe cell body Axons conductimpulses awayfrom the cellbodyFigure and Nerve ImpulsesAxons and Nerve Impulses Axons end in axonal terminals Axonal terminals contain vesicles withneurotransmittersSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummings Axonal terminals are separated from thenext neuron by a gap Synaptic cleft gap between adjacentneurons Synapse junction between nervesNerve Fiber CoveringsNerve Fiber Coverings Schwann cells produce myelinsheaths in jelly-rolllike fashionSlide 2003 Pearson Education, Inc.

7 Publishing as Benjamin Cummingslike fashion Nodes of Ranvier gaps in myelinsheath along theaxonFigure Cell Body LocationNeuron Cell Body Location Most are found in the central Nervous System inclusters called nuclei Bundles of nerve fibers in CNS = tracts Gray matter cell bodies andSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gray matter cell bodies andunmyelinated fibers White matter myelinated fibers Bundles of nerve fibers in PNS = nerves Ganglia collections of cell bodies outside thecentral Nervous systemFunctional Classification of NeuronsFunctional Classification of Neurons Sensory (afferent) neurons Cell bodies in a ganglion outside the CNS Carry impulses from the sensory receptors to CNS Cutaneous (skin) sense organsSlide 2003 Pearson Education, Inc.

8 Publishing as Benjamin Cummings Cutaneous (skin) sense organs Proprioceptors detect stretch or tension inmuscles, tendons, joints Motor (efferent) neurons Cell bodies found in the CNS Carry impulses from the central Nervous systemFunctional Classification of NeuronsFunctional Classification of Neurons Interneurons (association neurons) Found in neural pathways in the centralnervous systemSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummingsnervous System Cell bodies in the CNS Connect sensory and motor neuronsNeuron ClassificationNeuron ClassificationSlide 2003 Pearson Education, Inc. publishing as Benjamin CummingsFigure Classification of NeuronsStructural Classification of Neurons Multipolar neurons many extensionsfrom the cell bodySlide 2003 Pearson Education, Inc.

9 Publishing as Benjamin CummingsFigure Classification of NeuronsStructural Classification of Neurons Bipolar neurons one axon and onedendrite Rare in adults in eye and ear onlySlide 2003 Pearson Education, Inc. publishing as Benjamin CummingsFigure Classification of NeuronsStructural Classification of Neurons Unipolar neurons have a short, singleprocess leaving the cell body Axon conducts nerve impulses both to andfrom the cell bodySlide 2003 Pearson Education, Inc. publishing as Benjamin Cummingsfrom the cell bodyFigure Properties of NeuronsFunctional Properties of Neurons Two main functions Irritability ability to respond to stimuli Conductivity ability to transmit animpulseSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummingsimpulse The plasma membrane at rest is polarized Fewer positive ions (usually K+) are inside thecell than outside the cell (usually Na+)Starting a Nerve ImpulseStarting a Nerve Impulse Depolarization astimulus depolarizes theneuron s membrane A deploarized membraneallows sodium (Na+) toSlide 2003 Pearson Education, Inc.

10 Publishing as Benjamin Cummingsallows sodium (Na) toflow inside the membrane The exchange of ionsinitiates an actionpotential (nerve impulse)in the neuronFigure cThe Action PotentialThe Action Potential If the action potential (nerve impulse) starts, it ispropagated over the entire axon all-or-noneresponse Potassium ions rush out of the neuron aftersodium ions rush in, which repolarizes themembraneSlide 2003 Pearson Education, Inc. publishing as Benjamin Cummingsmembrane The sodium-potassium pump restores theoriginal configuration This action requires ATP Until repolarization occurs, a neuron cannotconduct another impulseNerve Impulse PropagationNerve Impulse Propagation The impulse continues tomove toward the cell body Impulses travel fasterwhen fibers have a myelinsheathSlide 2003 Pearson Education, Inc.