the nervous system. the master controlling and communication system of the master controlling and...
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The Nervous The Nervous SystemSystem
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The Nervous The Nervous SystemSystem
The master The master controlling controlling and and communicacommunication system tion system ofof
the bodythe body
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Three Overlapping Three Overlapping FunctionsFunctions
Sensory InputSensory Input Monitors internal and external stimuli Monitors internal and external stimuli
(Changes)(Changes) Afferent pathway to the brainAfferent pathway to the brain receptorsreceptors
IntegrationIntegration Processes and interprets informationProcesses and interprets information Decides the appropriate responseDecides the appropriate response
Motor OutputMotor Output Efferent pathway to effector organs Efferent pathway to effector organs
(muscles or glands), effects a response(muscles or glands), effects a response
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Organization of the Organization of the Nervous SystemNervous System
Central Nervous SystemCentral Nervous System (CNS) (CNS) Brain and spinal cordBrain and spinal cord Dorsal body cavityDorsal body cavity Integrating command centerIntegrating command center
Peripheral Nervous SystemPeripheral Nervous System (PNS) (PNS) Nerves to and from brain and spinal Nerves to and from brain and spinal
cordcord Communication links to the CNSCommunication links to the CNS Spinal nerves and cranial nervesSpinal nerves and cranial nerves
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Peripheral Nervous SystemPeripheral Nervous System
Sensory Afferent DivisionSensory Afferent Division Impulses to the brain and spinal cord Impulses to the brain and spinal cord
(CNS)(CNS) Monitors internal and external changesMonitors internal and external changes Somatic afferentSomatic afferent
Skin, skeletal muscle, jointsSkin, skeletal muscle, joints Visceral afferentVisceral afferent
Organs within ventral body cavityOrgans within ventral body cavity
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Peripheral Nervous SystemPeripheral Nervous System Motor Efferent DivisionMotor Efferent Division
From CNS to effector muscle, organs, and From CNS to effector muscle, organs, and glandsglands
Somatic efferent nervous systemSomatic efferent nervous system Voluntary nervous systemVoluntary nervous system
Autonomic nervous systemAutonomic nervous system InvoluntaryInvoluntary Visceral motor nerve fibers (to smooth and cardiac Visceral motor nerve fibers (to smooth and cardiac
muscle and glands)muscle and glands) Sympathetic (emergency situations)Sympathetic (emergency situations) Parasympathetic (conserves energy, nonemergency Parasympathetic (conserves energy, nonemergency
functions)functions)
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ClassificationClassification P. 224P. 224
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Nervous SystemNervous System
THE CELLS OF THE THE CELLS OF THE NERVOUS SYSTEMNERVOUS SYSTEM
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Nervous Tissue-Types of CellsNervous Tissue-Types of CellsTwo Principal Cell Types-Two Principal Cell Types- NeuronsNeurons: excitable nerve cells: excitable nerve cells Supporting cellsSupporting cells: : Neuroglia “Nerve Glue”Neuroglia “Nerve Glue”
Support, insulate, and protect neurons by Support, insulate, and protect neurons by surrounding and wrapping neurons.surrounding and wrapping neurons.
Central nervous system supporting cellsCentral nervous system supporting cells AstrocytesAstrocytes MicrogliaMicroglia Ependymal cellsEpendymal cells OligodendrocytesOligodendrocytes
Peripheral nervous system supporting cellsPeripheral nervous system supporting cells Satellite cellsSatellite cells Schwann cellsSchwann cells
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Neuroglia-Neuroglia-Supporting Cells Supporting Cells
of CNSof CNS
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AstrocytesAstrocytes Most abundantMost abundant *Star-shaped*Star-shaped Radiating processes cover neurons and anchor Radiating processes cover neurons and anchor
them to adjacent blood vesselsthem to adjacent blood vessels Controls exchange between blood vessels and Controls exchange between blood vessels and
neuronsneurons Determines capillary permeabilityDetermines capillary permeability
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Astrocytes (Cont)Astrocytes (Cont) Controls chemical environment around Controls chemical environment around
neuronsneurons Cleans up leaked potassium and recycling Cleans up leaked potassium and recycling
released neurotransmitterreleased neurotransmitter Guide migration of young neuronsGuide migration of young neurons
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MicrogliaMicroglia Small, ovoid cells, with thorny processes Small, ovoid cells, with thorny processes
(spider-like)(spider-like) Branches monitor health of neuronsBranches monitor health of neurons Migrate toward injured neuronMigrate toward injured neuron Transform into a macrophage when invading Transform into a macrophage when invading
microorganisms or dead neurons are present microorganisms or dead neurons are present and and disposedispose of debris of debris
Protective role because cells of immune Protective role because cells of immune system are denied access to CNSsystem are denied access to CNS
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Ependymal cellsEpendymal cells
Simple squamous to columnar in shapeSimple squamous to columnar in shape Line the cavities of the brain and spinal Line the cavities of the brain and spinal
cordcord Beating of their cilia circulates Beating of their cilia circulates
cerebrospinal fluid that cushions brain cerebrospinal fluid that cushions brain and spinal cordand spinal cord
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OligodendrocytesOligodendrocytes
Wrap cytoplasmic extensions around Wrap cytoplasmic extensions around neurons and form neurons and form myelin sheaths in myelin sheaths in CNSCNS
Insulates and protectsInsulates and protects
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Supporting Cells of the PNSSupporting Cells of the PNS
Satellite cellsSatellite cells Surround neuron cell bodies within gangliaSurround neuron cell bodies within ganglia Protective and cushioning cellsProtective and cushioning cells
Schwann cellsSchwann cells Surround and form myelin sheaths around Surround and form myelin sheaths around
larger nerve fiberslarger nerve fibers Functionally similar to oligodendrocytesFunctionally similar to oligodendrocytes
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NeuronsNeurons
Highly specialized to transmit Highly specialized to transmit nerve impulsesnerve impulses
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NeuronsNeurons Nerve cellsNerve cells Structural units of the nervous systemStructural units of the nervous system Special characteristics of neurons:Special characteristics of neurons:
1.1. Conduct nerve impulsesConduct nerve impulses2.2. Extreme longevityExtreme longevity3.3. Amiotic (exceptions: olfactory and hippocampus) Amiotic (exceptions: olfactory and hippocampus)
(become injured and do not regenerate)(become injured and do not regenerate)4.4. High metabolic rate: requires abundant oxygen High metabolic rate: requires abundant oxygen
and glucoseand glucose All Neurons have All Neurons have cell bodies cell bodies and and processesprocesses, ,
plus three functional components: receptive plus three functional components: receptive or input region, conducting component, and or input region, conducting component, and secretory or output component.secretory or output component.
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Cell BodyCell Body Metabolic centerMetabolic center No centriolesNo centrioles Ribosomes and rough ER (Ribosomes and rough ER (NisslNissl
SubstanceSubstance)most active of any cell in the )most active of any cell in the bodybody
Plasma membrane acts as part of the Plasma membrane acts as part of the receptive surfacereceptive surface
Most located within the CNS (called Most located within the CNS (called nucleinuclei))
Cell body collections in the PNS are called Cell body collections in the PNS are called gangliaganglia
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Cell ProcessesCell Processes Brain and spinal cord (CNS) contain both Brain and spinal cord (CNS) contain both
cell bodies and their processescell bodies and their processes The PNS consists chiefly of neuron The PNS consists chiefly of neuron
processesprocesses Bundles of neuron processes are calledBundles of neuron processes are called
tracts tracts (CNS) and (CNS) and nervesnerves (PNS). (PNS). DendritesDendrites
Short, tapering, hundreds/cellShort, tapering, hundreds/cell Receptive (input) region; convey incoming Receptive (input) region; convey incoming
messages(electrical signals) toward the cell messages(electrical signals) toward the cell bodybody
Large surface area Large surface area
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Cell ProcessesCell ProcessesAxonAxon (conducting component)(conducting component)
One Axon (Single process) per neuronOne Axon (Single process) per neuron Axon arises from Axon arises from axon hillock axon hillock of cell body of cell body Generates nerve impulses and transmits Generates nerve impulses and transmits
them away from the cell bodythem away from the cell body Long axons called nerve fibersLong axons called nerve fibersAxon terminals –Axon terminals –created where the axon created where the axon
branches at the terminal end branches at the terminal end 100-1000+ terminal branches per 100-1000+ terminal branches per
axon axon Axon terminals are the secretory portion—Axon terminals are the secretory portion—
secretes neurotransmitterssecretes neurotransmitters
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Myelin SheathMyelin Sheath (neurilemma)(neurilemma)
MyelinMyelin: whitish, fatty material covering long : whitish, fatty material covering long nerve fibers; has waxy appearancenerve fibers; has waxy appearance
Protects and provides an electrical insulation Protects and provides an electrical insulation covering for large and long nerve fiberscovering for large and long nerve fibers
Increases speed of transmission of nerve Increases speed of transmission of nerve impulsesimpulses
Unmyelinated fibers conduct impulses slowlyUnmyelinated fibers conduct impulses slowly Associated only with axons; Dendrites always Associated only with axons; Dendrites always
unmyelinatedunmyelinated Formed by Formed by Schwann cells Schwann cells in PNS—made of in PNS—made of
concentric layers of cell membranes (no concentric layers of cell membranes (no channel or carrier proteins) called the channel or carrier proteins) called the neurilemmaneurilemma
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Myelin (Cont)Myelin (Cont) Nodes of Ranvier Nodes of Ranvier are the gaps between are the gaps between
Schwann cells—regularly spacedSchwann cells—regularly spaced OligodendrocytesOligodendrocytes form CNS myelin sheaths— form CNS myelin sheaths—
coils around 60 fibers at the same time—no coils around 60 fibers at the same time—no neurilemma because of the absence of coiling neurilemma because of the absence of coiling of cellsof cells
Regions of the brain and spinal cord with Regions of the brain and spinal cord with myelinated fibers called myelinated fibers called white matter. white matter.
Gray matter Gray matter contains mostly cell bodies and contains mostly cell bodies and unmyelinated fibersunmyelinated fibers
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Classification of NeuronsClassification of Neurons Structural ClassificationStructural Classification
Multipolar neuronsMultipolar neurons Bipolar neuronsBipolar neurons Unipolar NeuronsUnipolar Neurons
Functional ClassificationFunctional Classification Sensory (afferent) neuronsSensory (afferent) neurons Motor (efferent) neuronsMotor (efferent) neurons Association (interneurons) neuronsAssociation (interneurons) neurons
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Nervous Tissue Nervous Tissue StructuresStructures
p. 227p. 227
CELL BODY
DENDRITE
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Nervous Tissue Nervous Tissue StructuresStructures
AXON
AXON TERMINAL
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Nervous Tissue Nervous Tissue StructuresStructures
SCHWANN CELLS
NODES OF RANVIER