Introduction to Biology - PowerPoint

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					The Nervous System:
part I



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Functions of the NS
  Monitoring body’s internal and
  external environments
  Integrating sensory information
  Directing and coordinating the
  actions of other body organs and
  systems


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Divisions of the NS
   Central Nervous System (CNS)
     brain
     spinal Cord

   Peripheral Nervous System (PNS)
     cranial nerves
     spinal nerves




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Divisions of the NS
   CNS: Responsible for reacting
   to sensory information and
   issuing motor commands
   PNS: Links the CNS to the rest
   of the body



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Divisions of the PNS
  Afferent
       Brings sensory info to the CNS
  Efferent
       Carries motor commands from CNS
        to muscles and glands




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Efferent Division of the PNS
   Somatic
       controls skeletal
        muscles
   Autonomic
       controls smooth
        muscle, cardiac
        muscle, glands, etc.



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Division of the Autonomic NS
   Sympathetic
   Parasympathetic




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Types of Neurons
   Sensory
   Motor
   Interneuron




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Sensory Neurons
   Part of afferent division
   Brings info from receptors
   outside of CNS




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Motor Neurons
  Part of efferent division
  Carries instructions from CNS to
  effectors (muscles, glands, etc)




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Interneurons
  Located within the CNS (brain
  and spinal cord)
  Responsible for Integrative
  Functions
    distribution and analysis of sensory
     information
    coordination of motor commands



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Neuron Structure
   Body (soma)
   Dendrites
   Axon
       Synaptic knobs




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Alternate Neuron Structures




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Neuroglia
  Supportive function
  Regulate chemical composition of
  extracellular fluid
  Engulf dead or invading cells




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Types of Neuroglia
  Astrocytes
       only in brain
  Oligodendrocytes (Schwann
  cells)
       forms myelin sheath around axons
  Microglia
       kind of white blood cell

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Myelin
 Glial cells wrap around axon
 (sheath) like a pancake around
 hotdog




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Nodes of Ranvier
  Area where there is no sheath are
  called nodes (Nodes of Ranvier)
  Gives “White Matter” its color




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Myelination
  Myelinated nerves transport signal
  faster than unmyelinated nerves




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Nerves
    Made up of bundles of axons




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Neuron Function
  There is a concentration gradient
  of charged ions between outside
  and inside of neruon’s cell
  membrane
      Na+ outside
      K+ inside
  Membrane potential is the
  difference in charge

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Action Potential
    Sudden localized change in
    membrane potential
    Formed from opening of “ion
    channels” for short period of
    time
    Polarized membrane suddenly
    depolarized then repolarized

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Action Potential




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Action Potential
  Generated by a stimulus
  “moves” down cell membrane
  toward synapse
  All or none
    no difference in size or duration




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Propagation
of signal




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Synapse
  Junction between 2
  neurons
  Contains:
     synaptic cleft
     presynaptic neuron

     postsynaptic neuron

     neurotransmitters




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Neurotransmitters
    Travel from presynaptic cell
    membrane across cleft toward
    postsynaptic membrane




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Types of Neurotransmitters
    Acetylcholine
    Epinephrine
    Norepinephrine
    Dopamine
    Serotonin



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Reflex Arc
    Simplest nerve
    response
    Involves one of each:
          Sensory neuron
          Motor neuron
          Interneuron (optional)




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