A and P 181 191
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A and P 181 191

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A and P 181 191 A and P 181 191 Presentation Transcript

  • Module#7 The Nervous SystemFunctions: Communication Coordination Control Gathering information
  • Differences betweenhuman and animal NS:1. Language2. Judgment3. Problem solving4. Creativeness5. Passing along heritage
  • Two Divisions of the NS1.Central nervous system (CNS)• the brain and spinal cord• is encased in bone (skull andvertebral column)
  • Two Divisions of the NS2. Peripheral nervous system(PNS)•nerves and ganglia that branchfrom the CNS and go to body.
  • Nerves – bundles of axons andtheir sheaths which extendfrom the CNSGanglia – collections of neuroncell bodies which are outsideof the CNS
  • CNS1. Brain •protected by cranium •high level thought •major organ of the NS •Message center •Uses info to formulate ideas •Makes decisions •Communicates with body
  • CNS1. Brain2. Spinal Cord Thick bundle nerve fibers within spinal cavity How brain communicates with most of body Ends at first lumbar
  • Peripheral NS1. Cranial nerves Nerves that come from brain 12 pairs Branch from brain stem Transmit from/to eyes, ears, mouth, face and scalp
  • Peripheral NS1. Cranial nerves2. Spinal Nerves Nerves that come from spinal cord 31 pairs Transmit signals to and from the rest of the body
  • Spinal nerves
  • Two divisions of Peripheral NS:1. Afferent sensory pathways - involves thesensory organs like eyes, ears..Neurons carry action potentialfrom sense organs to CNSAlso called sensory division
  • Two divisions of Peripheral NS:1. Afferent2. EfferentMotor pathways - system thatinnervates muscles, effectororgans, and glands.Also called motor division
  • Action potential – electrical signal thattravels along a neuron.
  • Divisions of the Efferent Nervous System:1. Somatic Motor Nervous System (SMNS) transmits action potential from CNS to skeletal muscles conscious, voluntary control
  • Divisions of the Efferent Nervous System:1. Somatic Motor Nervous System (SMNS)2. Autonomic NS carries stimulus from theCNS to the smoothmuscles, cardiac muscles, andglandsInvoluntary, unconscious
  • Divisions of the autonomic system:1. Sympathetic system•prepares body for physical activity•increases heart rate, bloodpressure, blood glucose levels•Prepares for “flight or fight”
  • Divisions of the autonomic system:1. Sympathetic system2. Parasympathetic:Regulates resting and nutritionallyrelated functionsIncludesdigestion, urination, defecationSlows down heart, etc. after “Fightor Flight” response
  • NS at a Cellular level:2 types of cells: 1. Neurons = functioning cell
  • Three parts of neurons (nerve cells):A. cell body contains the nucleus of cellB. dendrites –short, branched extensions of cellbodyreceive nerve impulses and conductthem toward the cell body
  • Three parts of neurons (nerve cells):A. cell bodyB. dendritesC. axonone long extension which carriesimpulses away from cell body to othercellshillock where the cell body ends andaxon begins
  • Axon continued:Is wrapped in a substance calledmyelin produced by neuroglial cellsmyelin speeds up impulsedMyelin is called Schwann in PNSand oligodendrocyte in CNSGaps in myelin called nodes ofRanvier
  • Axon continued :Axons vary in lengthAxon splits into collateralaxons and then end inpresynaptic terminals
  • Nerve impulses travel from the dendrite to body to axon.Collateral Axons
  • Mature neurons cannot undergo mitosis.They are parenchymapermanent cells!! TAKE CARE of them!!
  • But, Mrs. Crawfordhow can I take care ofthem?Get plenty ofsleep, avoid lots ofTV, avoidcaffeine, alcohol, drug
  • Well, how manyneurons do I have?It is believed you havearound 100 billion,some will die just dueto natural causes(about 7,000/day)
  • NS at a Cellular level continuedCan classify neurons based on their structure - how many processes they have (dendrites and axons):
  • 1.Unipolar –one process with a cell body that hangs off to the side2.Bipolar – two processes an axon and a single dendrite with the cell body in middle3. Multipolar –only one axon with many dentrites.
  • Bipolar multipolarunipolar
  • NS at a Cellular level continuedoWhat in the world is aassociation neuron Mrs.Crawford?A neuron that conducts action potentials forone neuron to another. (interneurons)
  • NS at a Cellular level:2 types of cells: 1. Neurons = functioning cell 2. NeurogliaBinds, protects and insulatesneuronsIs the majority of cells inthe NS.They do carry on mitosis!!
  • Types of Neuroglia :1.Schwann cells – insulate axons of PNS2. Oligodendrocytes – insulateaxons of CNS3. Microglia – white blood cells ofbrain
  • Types of Neuroglia :4. Astrocytes – form blood-brainbarrier regulating what can enterthe brain and what cannot. (Sometoxins pass through such as alcoholtoxins)
  • Types of Neuroglia :5. Ependymal cells – two types a. non – ciliated – secretecerebrospinal fluid b. ciliated – move cerebrospinalfluid around
  • Wrappings of the Nerve:Epineurium – wraps the nerve –white, shinyPerineurium – wraps the fasciclesEndoneurium – wraps theSchwann cells of axonsFascicles are bundles of axons
  • Nerve anatomy:Run along with veins andarteriesMedium sized = shoe stringSciatic nerve –largest, thickness of indexfinger
  • 3 Types of Nerves:1. Sensory – carries sensory messages only (optic nerve)2. Motor – carries messages to the muscles (eye muscles)3. Mixed – carries both
  • Healing in NervousSystem:•Neurons cannot undergomitosis.•Nerve healing occursunder certain conditions.
  • Conditions of nervehealing:•Axon is wrapped in Schwanncells which means only inPNS• Axon ends are close and pointed in right direction
  • Conditions of nervehealingNo healing in CNS, spinalcord or brainCan be surgically aided
  • Why are Schwann cells ableto aide in healing andoligodendrocytes not?There are many Schwanncells per axon in PNS, butmany axons peroligodendrocyte in the CNS.