Nervous system cells Ch. 12. Introduction to the nervous system video.

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Nervous system cellsNervous system cells

Ch. 12Ch. 12Ch. 12Ch. 12

Introduction to the nervous system videoIntroduction to the nervous system video



Nervous system IntroductionNervous system IntroductionFunction-Function-

communicationcommunicationComponents Components

Brain, spinal Brain, spinal cord, nervescord, nerves

Function-Function-communicationcommunication

Components Components Brain, spinal Brain, spinal

cord, nervescord, nerves QuickTime™ and a decompressor


Organization of the nervous systemOrganization of the nervous system SubdivisionsSubdivisions

Central Nervous system (CNS)Central Nervous system (CNS) Structural/functional centerStructural/functional center Brain,spinal cordBrain,spinal cord Integrate sensory informationIntegrate sensory information Evaluate sensory informationEvaluate sensory information Initiate outgoing responseInitiate outgoing response

Peripheral Nervous system (PNS)Peripheral Nervous system (PNS) NervesNerves

Cranial-from brainCranial-from brain Spinal-from spinal cordSpinal-from spinal cord

Afferent and efferent divisionsAfferent and efferent divisions Afferent - information from environmentAfferent - information from environment Efferent-from brain to muscles/glandsEfferent-from brain to muscles/glands

SubdivisionsSubdivisions Central Nervous system (CNS)Central Nervous system (CNS)

Structural/functional centerStructural/functional center Brain,spinal cordBrain,spinal cord Integrate sensory informationIntegrate sensory information Evaluate sensory informationEvaluate sensory information Initiate outgoing responseInitiate outgoing response

Peripheral Nervous system (PNS)Peripheral Nervous system (PNS) NervesNerves

Cranial-from brainCranial-from brain Spinal-from spinal cordSpinal-from spinal cord

Afferent and efferent divisionsAfferent and efferent divisions Afferent - information from environmentAfferent - information from environment Efferent-from brain to muscles/glandsEfferent-from brain to muscles/glands

InnervationInnervation

Somatic - carries info to musclesSomatic - carries info to muscles Autonomic-carries info to smooth Autonomic-carries info to smooth

and cardiac muscleand cardiac muscle Efferent divisionEfferent division

Sympathetic - (fight or flight)Sympathetic - (fight or flight) Parasympathetic-normal resting activities Parasympathetic-normal resting activities

(rest/repair)(rest/repair) Visceral sensory division--Visceral sensory division--

communicating between viscera and communicating between viscera and brain - continualbrain - continual

Somatic - carries info to musclesSomatic - carries info to muscles Autonomic-carries info to smooth Autonomic-carries info to smooth

and cardiac muscleand cardiac muscle Efferent divisionEfferent division

Sympathetic - (fight or flight)Sympathetic - (fight or flight) Parasympathetic-normal resting activities Parasympathetic-normal resting activities

(rest/repair)(rest/repair) Visceral sensory division--Visceral sensory division--

communicating between viscera and communicating between viscera and brain - continualbrain - continual

Cells of the nervous systemCells of the nervous system Glia - supportive functionGlia - supportive function

TypesTypes Astrocytes-star shapedAstrocytes-star shaped

Most numerousMost numerous Connect to neurons and capillariesConnect to neurons and capillaries Transfer nutrients from blood to Transfer nutrients from blood to

neuronsneurons Make up blood brain barrierMake up blood brain barrier

Microglia-smallMicroglia-small If brain is inflamed, phagocytosisIf brain is inflamed, phagocytosis

Ependymal-thin sheets that line Ependymal-thin sheets that line cavities of cnscavities of cns

Produce and circulate fluidProduce and circulate fluid Oligodendrocytes-hold nerve fibers Oligodendrocytes-hold nerve fibers

together and produce myelin sheathtogether and produce myelin sheath Schwann-in pnsSchwann-in pns

Form myelin sheathForm myelin sheath Gaps-nodes of ranvierGaps-nodes of ranvier Essential for nerve regrowthEssential for nerve regrowth

Glia - supportive functionGlia - supportive function TypesTypes

Astrocytes-star shapedAstrocytes-star shaped Most numerousMost numerous Connect to neurons and capillariesConnect to neurons and capillaries Transfer nutrients from blood to Transfer nutrients from blood to

neuronsneurons Make up blood brain barrierMake up blood brain barrier

Microglia-smallMicroglia-small If brain is inflamed, phagocytosisIf brain is inflamed, phagocytosis

Ependymal-thin sheets that line Ependymal-thin sheets that line cavities of cnscavities of cns

Produce and circulate fluidProduce and circulate fluid Oligodendrocytes-hold nerve fibers Oligodendrocytes-hold nerve fibers

together and produce myelin sheathtogether and produce myelin sheath Schwann-in pnsSchwann-in pns

Form myelin sheathForm myelin sheath Gaps-nodes of ranvierGaps-nodes of ranvier Essential for nerve regrowthEssential for nerve regrowth

MicrogliaMicroglia



Cells of the nervous systemCells of the nervous system Neurons-excitable cells that Neurons-excitable cells that

conduct impulsesconduct impulses StructureStructure

Cell body-ribosomes make Cell body-ribosomes make neurotransmitters which are neurotransmitters which are packaged into vessiclespackaged into vessicles

Dendrites-one or more per neuronDendrites-one or more per neuron Conduct nerve signals to cell Conduct nerve signals to cell

bodybody Distal ends of sensory neurons Distal ends of sensory neurons

are receptorsare receptors Axon-single process extending Axon-single process extending

from axon hillockfrom axon hillock Sometimes covered with myelin - Sometimes covered with myelin -

fatty layerfatty layer Conducts nerve impulses away Conducts nerve impulses away

from cell bodyfrom cell body Synaptic knob at endSynaptic knob at end

Cytoskeleton- neurofibrils - allow Cytoskeleton- neurofibrils - allow rapid transport rapid transport

Neurons-excitable cells that Neurons-excitable cells that conduct impulsesconduct impulses StructureStructure

Cell body-ribosomes make Cell body-ribosomes make neurotransmitters which are neurotransmitters which are packaged into vessiclespackaged into vessicles

Dendrites-one or more per neuronDendrites-one or more per neuron Conduct nerve signals to cell Conduct nerve signals to cell

bodybody Distal ends of sensory neurons Distal ends of sensory neurons

are receptorsare receptors Axon-single process extending Axon-single process extending

from axon hillockfrom axon hillock Sometimes covered with myelin - Sometimes covered with myelin -

fatty layerfatty layer Conducts nerve impulses away Conducts nerve impulses away

from cell bodyfrom cell body Synaptic knob at endSynaptic knob at end

Cytoskeleton- neurofibrils - allow Cytoskeleton- neurofibrils - allow rapid transport rapid transport

Functional regionsFunctional regions

Input - dendrites/cell bodyInput - dendrites/cell bodySummation-axon hillockSummation-axon hillockConduction-axonConduction-axonOutput -synaptic knobsOutput -synaptic knobs

Input - dendrites/cell bodyInput - dendrites/cell bodySummation-axon hillockSummation-axon hillockConduction-axonConduction-axonOutput -synaptic knobsOutput -synaptic knobs

Classification of neuronsClassification of neurons

Structural classificationStructural classification Multipolar-1axon, several dendritesMultipolar-1axon, several dendrites Bipolar-1axon,1dendriteBipolar-1axon,1dendrite Unipolar-1axon which divides into 2Unipolar-1axon which divides into 2

Functional classificationFunctional classification Afferent-sensory neuron(conduct impulses to Afferent-sensory neuron(conduct impulses to

spinal cord or brain)spinal cord or brain) Efferent-motor neuron(conduct impulses from Efferent-motor neuron(conduct impulses from

brain to muscle or gland)brain to muscle or gland) Interneurons (bridge gap between sensory and Interneurons (bridge gap between sensory and

motor )motor )

Structural classificationStructural classification Multipolar-1axon, several dendritesMultipolar-1axon, several dendrites Bipolar-1axon,1dendriteBipolar-1axon,1dendrite Unipolar-1axon which divides into 2Unipolar-1axon which divides into 2

Functional classificationFunctional classification Afferent-sensory neuron(conduct impulses to Afferent-sensory neuron(conduct impulses to

spinal cord or brain)spinal cord or brain) Efferent-motor neuron(conduct impulses from Efferent-motor neuron(conduct impulses from

brain to muscle or gland)brain to muscle or gland) Interneurons (bridge gap between sensory and Interneurons (bridge gap between sensory and

motor )motor )

Reflex arcReflex arc Signal conduction Signal conduction

route - from receptor route - from receptor to and from CNSto and from CNS

3 neuron arc-most 3 neuron arc-most common - afferent common - afferent neuron, interneuron neuron, interneuron and efferent neuronand efferent neuron

Two neuron arc-Two neuron arc-simplest form - simplest form - afferent and efferent afferent and efferent neuronneuron

Signal conduction Signal conduction route - from receptor route - from receptor to and from CNSto and from CNS

3 neuron arc-most 3 neuron arc-most common - afferent common - afferent neuron, interneuron neuron, interneuron and efferent neuronand efferent neuron

Two neuron arc-Two neuron arc-simplest form - simplest form - afferent and efferent afferent and efferent neuronneuron

Synapse-Where nerve signals are transmitted from one neuron to anotherSynapse-Where nerve signals are transmitted from one neuron to another

TypesTypes Electrical-Electrical-

electrical current electrical current jumps gapjumps gap

Chemical - Chemical - typical in adultstypical in adults

Located at Located at junction of junction of synaptic knob of synaptic knob of one neuron and one neuron and dendrite/cell dendrite/cell body of anotherbody of another

TypesTypes Electrical-Electrical-

electrical current electrical current jumps gapjumps gap

Chemical - Chemical - typical in adultstypical in adults

Located at Located at junction of junction of synaptic knob of synaptic knob of one neuron and one neuron and dendrite/cell dendrite/cell body of anotherbody of another

Nerves-bundles of fibers held together with connective tissueNerves-bundles of fibers held together with connective tissue Connective tissueConnective tissue

Endoneurium-surround Endoneurium-surround each fibereach fiber

Perineurium-hold together Perineurium-hold together bundles of nerves bundles of nerves (fascicles)(fascicles)

Epineurium-surround many Epineurium-surround many fascicles/bloodfascicles/blood

Tracts-bundles of nerve Tracts-bundles of nerve fibers in CNSfibers in CNS

White matter - myelinated White matter - myelinated nervesnerves

Gray matter-cell bodies, Gray matter-cell bodies, dendritesdendrites

Nerves can be afferent, Nerves can be afferent, efferent or Mixedefferent or Mixed

Connective tissueConnective tissue Endoneurium-surround Endoneurium-surround

each fibereach fiber Perineurium-hold together Perineurium-hold together

bundles of nerves bundles of nerves (fascicles)(fascicles)

Epineurium-surround many Epineurium-surround many fascicles/bloodfascicles/blood

Tracts-bundles of nerve Tracts-bundles of nerve fibers in CNSfibers in CNS

White matter - myelinated White matter - myelinated nervesnerves

Gray matter-cell bodies, Gray matter-cell bodies, dendritesdendrites

Nerves can be afferent, Nerves can be afferent, efferent or Mixedefferent or Mixed

Repair of nerve fibersRepair of nerve fibers If the cell dies, the damage If the cell dies, the damage

is permanent. is permanent. If the axon is damaged, If the axon is damaged,

the axon can bypass the the axon can bypass the damage and re-grow. damage and re-grow.

Stages of repairStages of repair Axon degeneration and Axon degeneration and

Removal of debris by Removal of debris by phagocytosis.phagocytosis.

Growth bypasses the Growth bypasses the damaged axon with new damaged axon with new axon formationaxon formation

Schwann cells cover the Schwann cells cover the new growthnew growth

If the cell dies, the damage If the cell dies, the damage is permanent. is permanent.

If the axon is damaged, If the axon is damaged, the axon can bypass the the axon can bypass the damage and re-grow. damage and re-grow.

Stages of repairStages of repair Axon degeneration and Axon degeneration and

Removal of debris by Removal of debris by phagocytosis.phagocytosis.

Growth bypasses the Growth bypasses the damaged axon with new damaged axon with new axon formationaxon formation

Schwann cells cover the Schwann cells cover the new growthnew growth

Nerve ImpulsesNerve Impulses

Living cells maintain a difference in the concentration across Living cells maintain a difference in the concentration across membranesmembranes

Membrane potential - excess of positively charged ions Membrane potential - excess of positively charged ions outside membrane, negatively charged insideoutside membrane, negatively charged inside

Polarized membrane-exhibits this differencePolarized membrane-exhibits this difference Magnitude measured in Volts or millivolts (mv).Magnitude measured in Volts or millivolts (mv). Resting membrane potential is normally -70mv.Resting membrane potential is normally -70mv.

Sodium potassium pump (active transport)-produces slight Sodium potassium pump (active transport)-produces slight excess of pos. ions outside. Transports sodium/potassium excess of pos. ions outside. Transports sodium/potassium inside/outside.inside/outside.

Local potential-slight shift away from resting potentialLocal potential-slight shift away from resting potential Excitation occurs when -dditional sodium channels opened Excitation occurs when -dditional sodium channels opened

(sodium is positively charged)allows potential to move towards (sodium is positively charged)allows potential to move towards 0 (depolarization)0 (depolarization)

Action potential occurs when a certain number of sodium ions Action potential occurs when a certain number of sodium ions diffuse inward.diffuse inward.

To resotre the neuron to resting potential, Inhibition occurs - To resotre the neuron to resting potential, Inhibition occurs - potassium channels open increasing potential (potassium channels open increasing potential (

Living cells maintain a difference in the concentration across Living cells maintain a difference in the concentration across membranesmembranes

Membrane potential - excess of positively charged ions Membrane potential - excess of positively charged ions outside membrane, negatively charged insideoutside membrane, negatively charged inside

Polarized membrane-exhibits this differencePolarized membrane-exhibits this difference Magnitude measured in Volts or millivolts (mv).Magnitude measured in Volts or millivolts (mv). Resting membrane potential is normally -70mv.Resting membrane potential is normally -70mv.

Sodium potassium pump (active transport)-produces slight Sodium potassium pump (active transport)-produces slight excess of pos. ions outside. Transports sodium/potassium excess of pos. ions outside. Transports sodium/potassium inside/outside.inside/outside.

Local potential-slight shift away from resting potentialLocal potential-slight shift away from resting potential Excitation occurs when -dditional sodium channels opened Excitation occurs when -dditional sodium channels opened

(sodium is positively charged)allows potential to move towards (sodium is positively charged)allows potential to move towards 0 (depolarization)0 (depolarization)

Action potential occurs when a certain number of sodium ions Action potential occurs when a certain number of sodium ions diffuse inward.diffuse inward.

To resotre the neuron to resting potential, Inhibition occurs - To resotre the neuron to resting potential, Inhibition occurs - potassium channels open increasing potential (potassium channels open increasing potential (

Action potential mechanismAction potential mechanism Stimulus triggers sodium gates Stimulus triggers sodium gates

to opento open Sodium moves into cellSodium moves into cell Threshold potential point at Threshold potential point at

which impulse is triggeredwhich impulse is triggered All or noneAll or none Gates stay open for a short Gates stay open for a short

time then closetime then close Movement to resting potential Movement to resting potential

when potassium channels when potassium channels open (repolarization)open (repolarization)

Hyperpolarization precedes Hyperpolarization precedes achieving resting potential achieving resting potential againagain

Refractory period-membrane Refractory period-membrane resists repolarization (brief)resists repolarization (brief)

Stimulus triggers sodium gates Stimulus triggers sodium gates to opento open

Sodium moves into cellSodium moves into cell Threshold potential point at Threshold potential point at

which impulse is triggeredwhich impulse is triggered All or noneAll or none Gates stay open for a short Gates stay open for a short

time then closetime then close Movement to resting potential Movement to resting potential

when potassium channels when potassium channels open (repolarization)open (repolarization)

Hyperpolarization precedes Hyperpolarization precedes achieving resting potential achieving resting potential againagain

Refractory period-membrane Refractory period-membrane resists repolarization (brief)resists repolarization (brief)



Action potential conductionAction potential conduction Reverse of polarity at peak of action Reverse of polarity at peak of action

potentialpotential Reversal causes electrical current to flow Reversal causes electrical current to flow

between membrane regions and triggers between membrane regions and triggers sodium channels to open in next segment.sodium channels to open in next segment.

This repeatsThis repeats Action potential never moves backward Action potential never moves backward

because of refractory periodbecause of refractory period In myelenated axons, action potentials only In myelenated axons, action potentials only

occur at nodes of ranvier, jumping to next occur at nodes of ranvier, jumping to next node - called Saltatory conductionnode - called Saltatory conduction

Speed of conduction-depends on diameter Speed of conduction-depends on diameter of fiber and presence or absence of myelin.of fiber and presence or absence of myelin.

Reverse of polarity at peak of action Reverse of polarity at peak of action potentialpotential

Reversal causes electrical current to flow Reversal causes electrical current to flow between membrane regions and triggers between membrane regions and triggers sodium channels to open in next segment.sodium channels to open in next segment.

This repeatsThis repeats Action potential never moves backward Action potential never moves backward

because of refractory periodbecause of refractory period In myelenated axons, action potentials only In myelenated axons, action potentials only

occur at nodes of ranvier, jumping to next occur at nodes of ranvier, jumping to next node - called Saltatory conductionnode - called Saltatory conduction

Speed of conduction-depends on diameter Speed of conduction-depends on diameter of fiber and presence or absence of myelin.of fiber and presence or absence of myelin.

Types of synapsesTypes of synapses

Electrical-action Electrical-action potential continues to potential continues to postsynaptic membranepostsynaptic membrane

Chemical-presynaptic Chemical-presynaptic cells release chemical cells release chemical messengers messengers (neurotransmitters) (neurotransmitters) across gap to across gap to postsynaptic cell, postsynaptic cell, inducing action inducing action potential. potential.

Electrical-action Electrical-action potential continues to potential continues to postsynaptic membranepostsynaptic membrane

Chemical-presynaptic Chemical-presynaptic cells release chemical cells release chemical messengers messengers (neurotransmitters) (neurotransmitters) across gap to across gap to postsynaptic cell, postsynaptic cell, inducing action inducing action potential. potential.

Mechanism of synaptic transmissionMechanism of synaptic transmission

Action potential releases calciumAction potential releases calciumNeurotransmitter releaseNeurotransmitter releaseNeurotransmitter diffusionNeurotransmitter diffusionPost synaptic potentialPost synaptic potentialNeurotransmitter action termination by Neurotransmitter action termination by

re-uptake or taken up by gliare-uptake or taken up by glia

Action potential releases calciumAction potential releases calciumNeurotransmitter releaseNeurotransmitter releaseNeurotransmitter diffusionNeurotransmitter diffusionPost synaptic potentialPost synaptic potentialNeurotransmitter action termination by Neurotransmitter action termination by

re-uptake or taken up by gliare-uptake or taken up by glia

NeurotransmittersNeurotransmitters

Description-chemical Description-chemical communicatorscommunicators

Function - can be Function - can be excitatory or inhibibitoryexcitatory or inhibibitory

Classes of Classes of neurotransmittersneurotransmitters

AcetylcholineAcetylcholine Amines affect learning, Amines affect learning,

emotions, motor controlemotions, motor control Amino acids - most Amino acids - most

common. Location - common. Location - PNSPNS

Description-chemical Description-chemical communicatorscommunicators

Function - can be Function - can be excitatory or inhibibitoryexcitatory or inhibibitory

Classes of Classes of neurotransmittersneurotransmitters

AcetylcholineAcetylcholine Amines affect learning, Amines affect learning,

emotions, motor controlemotions, motor control Amino acids - most Amino acids - most

common. Location - common. Location - PNSPNS



Neurotransmitter stimulation of post-synaptic membraneNeurotransmitter stimulation of post-synaptic membrane

Direct stimulation second messengerDirect stimulation second messengerDirect stimulation second messengerDirect stimulation second messenger

AnaestheticsAnaesthetics

Reduce pain sensation by the followingReduce pain sensation by the following Blocks initiation or conduction of nerve Blocks initiation or conduction of nerve

impulseimpulse Inhibit sodium channel openingInhibit sodium channel opening

Reduce pain sensation by the followingReduce pain sensation by the following Blocks initiation or conduction of nerve Blocks initiation or conduction of nerve

impulseimpulse Inhibit sodium channel openingInhibit sodium channel opening

Antidepressants Antidepressants

Depression - deficit of norepinephrine, Depression - deficit of norepinephrine, dopamine, serotonindopamine, serotonin Possible causes:Possible causes:

Neurotransmitters are not present in the synaptic cleft in Neurotransmitters are not present in the synaptic cleft in enough quantityenough quantity

Neurotransmitters are receycled too quicklyNeurotransmitters are receycled too quickly Neurotransmitters are not produced by the ribosomesin Neurotransmitters are not produced by the ribosomesin

enough quantitiyenough quantitiy Drugs inhibit the enzymes that inactivate Drugs inhibit the enzymes that inactivate

neurotransmittersneurotransmitters Inhibit reuptake of neurotransmittersInhibit reuptake of neurotransmitters

Depression - deficit of norepinephrine, Depression - deficit of norepinephrine, dopamine, serotonindopamine, serotonin Possible causes:Possible causes:

Neurotransmitters are not present in the synaptic cleft in Neurotransmitters are not present in the synaptic cleft in enough quantityenough quantity

Neurotransmitters are receycled too quicklyNeurotransmitters are receycled too quickly Neurotransmitters are not produced by the ribosomesin Neurotransmitters are not produced by the ribosomesin

enough quantitiyenough quantitiy Drugs inhibit the enzymes that inactivate Drugs inhibit the enzymes that inactivate

neurotransmittersneurotransmitters Inhibit reuptake of neurotransmittersInhibit reuptake of neurotransmitters

Cycle of lifeCycle of life

Nerve tissue developmentNerve tissue development Begins in fetal ectodermBegins in fetal ectoderm Learning - formation of new synapsesLearning - formation of new synapses

Aging - degenerationAging - degeneration

Nerve tissue developmentNerve tissue development Begins in fetal ectodermBegins in fetal ectoderm Learning - formation of new synapsesLearning - formation of new synapses

Aging - degenerationAging - degeneration

Nervous system cells Ch. 12. Introduction to the nervous system video.

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