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
Two divisions of Peripheral NS:1. Afferent sensory pathways - involves thesensory organs like eyes, ears..Neurons carry action potentialfrom sense organs to CNSAlso called sensory division
Two divisions of Peripheral NS:1. Afferent2. EfferentMotor 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, andglandsInvoluntary, 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 functionsIncludesdigestion, urination, defecationSlows 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 cellbodyreceive nerve impulses and conductthem toward the cell body
Three parts of neurons (nerve cells):A. cell bodyB. dendritesC. axonone long extension which carriesimpulses away from cell body to othercellshillock where the cell body ends andaxon begins
Axon continued:Is wrapped in a substance calledmyelin produced by neuroglial cellsmyelin speeds up impulsedMyelin is called Schwann in PNSand oligodendrocyte in CNSGaps in myelin called nodes ofRanvier
Axon continued :Axons vary in lengthAxon 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.
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. NeurogliaBinds, protects and insulatesneuronsIs 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, shinyPerineurium – wraps the fasciclesEndoneurium – wraps theSchwann cells of axonsFascicles are bundles of axons
Nerve anatomy:Run along with veins andarteriesMedium sized = shoe stringSciatic 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 nervehealingNo healing in CNS, spinalcord or brainCan 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.