Chapter 12INTRODUCTIONChapter 12 Nervous TissueMajor Structures of the Nervous SystemStructures of the Nervous System - OverviewFunctions of the Nervous SystemsNervous System DivisionsSubdivisions of the PNSOrganization of the Nervous SystemEnteric NSHISTOLOGY OF THE NERVOUS SYSTEMNeuronal Structure & FunctionNeuronsParts of a NeuronCell membraneDendritesAxonsAxonal TransportAxonal Transport & DiseaseDiversity in NeuronsStructural Classification of NeuronsFunctional Classification of NeuronsAssociation or InterneuronsNeuroglial CellsAstrocytesMicrogliaEpendymal cellsSatellite CellsOligodendrocytesMyelinationSchwann CellAxon Coverings in PNSMyelination in PNSMyelination in the CNSGray and White MatterElectrical Signals in NeuronsTwo Types of Ion ChannelsIon ChannelsGated Ion ChannelsResting Membrane PotentialSlide 41Graded PotentialsHow do Graded Potentials Arise?Generation of an Action PotentialAction PotentialDepolarizing Phase of Action PotentialRepolarizing Phase of Action PotentialRefractory Period of Action PotentialThe Action Potential: SummarizedLocal AnestheticsPropagation of Action PotentialContinuous versus Saltatory ConductionSaltatory ConductionSpeed of Impulse PropagationEncoding of Stimulus IntensityAction Potentials in Nerve and MuscleSIGNAL TRANSMISSION AT SYNAPSESSignal Transmission at SynapsesSlide 59Chemical SynapsesExcitatory & Inhibitory PotentialsRemoval of NeurotransmitterThree Possible ResponsesComparison of Graded & Action PotentialsSlide 65SummationSpatial SummationTemporal SummationSlide 69NeurotransmittersNeurotransmitter EffectsSmall-Molecule NeurotransmittersSlide 73Slide 74NeuropeptidesStrychnine PoisoningNeuronal CircuitsSlide 78Regeneration & RepairDamage and Repair in the Peripheral Nervous System (Figure 19.a)Repair within the PNSSlide 82Neurogenesis in the CNSMultiple Sclerosis (MS)EpilepsySlide 86Principles of Human Anatomy and Physiology, 11e 1Chapter 12Nervous TissueLecture OutlinePrinciples of Human Anatomy and Physiology, 11e 2INTRODUCTION•The nervous system, along with the endocrine system, helps to keep controlled conditions within limits that maintain health and helps to maintain homeostasis.•The nervous system is responsible for all our behaviors, memories, and movements.•The branch of medical science that deals with the normal functioning and disorders of the nervous system is called neurology.Principles of Human Anatomy and Physiology, 11e 3Chapter 12Nervous Tissue•Controls and integrates all body activities within limits that maintain life•Three basic functions–sensing changes with sensory receptors•fullness of stomach or sun on your face–interpreting and remembering those changes–reacting to those changes with effectors•muscular contractions•glandular secretionsPrinciples of Human Anatomy and Physiology, 11e 4Major Structures of the Nervous System•Brain, cranial nerves, spinal cord, spinal nerves, ganglia, enteric plexuses and sensory receptorsPrinciples of Human Anatomy and Physiology, 11e 5Structures of the Nervous System - Overview•Twelve pairs of cranial nerves emerge from the base of the brain through foramina of the skull.–A nerve is a bundle of hundreds or thousands of axons, each of which courses along a defined path and serves a specific region of the body.•The spinal cord connects to the brain through the foramen magnum of the skull and is encircled by the bones of the vertebral column.–Thirty-one pairs of spinal nerves emerge from the spinal cord, each serving a specific region of the body.•Ganglia, located outside the brain and spinal cord, are small masses of nervous tissue, containing primarily cell bodies of neurons.•Enteric plexuses help regulate the digestive system.•Sensory receptors are either parts of neurons or specialized cells that monitor changes in the internal or external environment.Principles of Human Anatomy and Physiology, 11e 6Functions of the Nervous Systems•The sensory function of the nervous system is to sense changes in the internal and external environment through sensory receptors. –Sensory (afferent) neurons serve this function.•The integrative function is to analyze the sensory information, store some aspects, and make decisions regarding appropriate behaviors. –Association or interneurons serve this function.•The motor function is to respond to stimuli by initiating action. –Motor(efferent) neurons serve this function.Principles of Human Anatomy and Physiology, 11e 7Nervous System Divisions•Central nervous system (CNS) –consists of the brain and spinal cord•Peripheral nervous system (PNS)– consists of cranial and spinal nerves that contain both sensory and motor fibers–connects CNS to muscles, glands & all sensory receptorsPrinciples of Human Anatomy and Physiology, 11e 8Subdivisions of the PNS•Somatic (voluntary) nervous system (SNS)–neurons from cutaneous and special sensory receptors to the CNS–motor neurons to skeletal muscle tissue•Autonomic (involuntary) nervous systems–sensory neurons from visceral organs to CNS–motor neurons to smooth & cardiac muscle and glands•sympathetic division (speeds up heart rate)•parasympathetic division (slow down heart rate)•Enteric nervous system (ENS)–involuntary sensory & motor neurons control GI tract–neurons function independently of ANS & CNSPrinciples of Human Anatomy and Physiology, 11e 9Organization of the Nervous System•CNS is brain and spinal cord•PNS is everything elsePrinciples of Human Anatomy and Physiology, 11e 10Enteric NS•The enteric nervous system (ENS) consists of neurons in enteric plexuses that extend the length of the GI tract.–Many neurons of the enteric plexuses function independently of the ANS and CNS.–Sensory neurons of the ENS monitor chemical changes within the GI tract and stretching of its walls, whereas enteric motor neurons govern contraction of GI tract organs, and activity of the GI tract endocrine cells.Principles of Human Anatomy and Physiology, 11e 11HISTOLOGY OF THE NERVOUS SYSTEMPrinciples of Human Anatomy and Physiology, 11e 12Neuronal Structure & FunctionPrinciples of Human Anatomy and Physiology, 11e 13Neurons•Functional unit of nervous system•Have capacity to produce action potentials–electrical excitability•Cell body–single nucleus with prominent nucleolus–Nissl bodies (chromatophilic substance) •rough ER & free ribosomes for protein synthesis–neurofilaments give cell shape and support–microtubules