A and P 181 191


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A and P 181 191

  1. 1. Module#7 The Nervous SystemFunctions: Communication Coordination Control Gathering information
  2. 2. Differences betweenhuman and animal NS:1. Language2. Judgment3. Problem solving4. Creativeness5. Passing along heritage
  3. 3. Two Divisions of the NS1.Central nervous system (CNS)• the brain and spinal cord• is encased in bone (skull andvertebral column)
  4. 4. Two Divisions of the NS2. Peripheral nervous system(PNS)•nerves and ganglia that branchfrom the CNS and go to body.
  5. 5. Nerves – bundles of axons andtheir sheaths which extendfrom the CNSGanglia – collections of neuroncell bodies which are outsideof the CNS
  6. 6. 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
  7. 7. CNS1. Brain2. Spinal Cord Thick bundle nerve fibers within spinal cavity How brain communicates with most of body Ends at first lumbar
  8. 8. Peripheral NS1. Cranial nerves Nerves that come from brain 12 pairs Branch from brain stem Transmit from/to eyes, ears, mouth, face and scalp
  9. 9. Peripheral NS1. Cranial nerves2. Spinal Nerves Nerves that come from spinal cord 31 pairs Transmit signals to and from the rest of the body
  10. 10. Spinal nerves
  11. 11. 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
  12. 12. Two divisions of Peripheral NS:1. Afferent2. EfferentMotor pathways - system thatinnervates muscles, effectororgans, and glands.Also called motor division
  13. 13. Action potential – electrical signal thattravels along a neuron.
  14. 14. Divisions of the Efferent Nervous System:1. Somatic Motor Nervous System (SMNS) transmits action potential from CNS to skeletal muscles conscious, voluntary control
  15. 15. 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
  16. 16. 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”
  17. 17. 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
  18. 18. NS at a Cellular level:2 types of cells: 1. Neurons = functioning cell
  19. 19. 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
  20. 20. 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
  21. 21. 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
  22. 22. Axon continued :Axons vary in lengthAxon splits into collateralaxons and then end inpresynaptic terminals
  23. 23. Nerve impulses travel from the dendrite to body to axon.Collateral Axons
  24. 24. Mature neurons cannot undergo mitosis.They are parenchymapermanent cells!! TAKE CARE of them!!
  25. 25. But, Mrs. Crawfordhow can I take care ofthem?Get plenty ofsleep, avoid lots ofTV, avoidcaffeine, alcohol, drug
  26. 26. Well, how manyneurons do I have?It is believed you havearound 100 billion,some will die just dueto natural causes(about 7,000/day)
  27. 27. NS at a Cellular level continuedCan classify neurons based on their structure - how many processes they have (dendrites and axons):
  28. 28. 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.
  29. 29. Bipolar multipolarunipolar
  30. 30. 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)
  31. 31. 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!!
  32. 32. Types of Neuroglia :1.Schwann cells – insulate axons of PNS2. Oligodendrocytes – insulateaxons of CNS3. Microglia – white blood cells ofbrain
  33. 33. Types of Neuroglia :4. Astrocytes – form blood-brainbarrier regulating what can enterthe brain and what cannot. (Sometoxins pass through such as alcoholtoxins)
  34. 34. Types of Neuroglia :5. Ependymal cells – two types a. non – ciliated – secretecerebrospinal fluid b. ciliated – move cerebrospinalfluid around
  35. 35. 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
  36. 36. Nerve anatomy:Run along with veins andarteriesMedium sized = shoe stringSciatic nerve –largest, thickness of indexfinger
  37. 37. 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
  38. 38. Healing in NervousSystem:•Neurons cannot undergomitosis.•Nerve healing occursunder certain conditions.
  39. 39. Conditions of nervehealing:•Axon is wrapped in Schwanncells which means only inPNS• Axon ends are close and pointed in right direction
  40. 40. Conditions of nervehealingNo healing in CNS, spinalcord or brainCan be surgically aided
  41. 41. Why are Schwann cells ableto aide in healing andoligodendrocytes not?There are many Schwanncells per axon in PNS, butmany axons peroligodendrocyte in the CNS.