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Crash course Nervous system

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					 Crash course:
Nervous system
          Three Functions
 1.  Sensory input: signals conducted
  from sensory cells in body (heat,
  touch, hearing, balance, vision, smell,
  taste, etc.)
 2. Integration: information
  interpreted and processed (in brain
  and spinal cord).
 3. Motor output: signals carried to
  muscles and glands.
                 Two Parts
 Central nervous system – processes
  information; brain and spinal cord; covered by
  protective meninges layers and bathed in
  cerebrospinal fluid.
 Spinal cord incased in vertebral column;
  simple stimuli and responses (reflexes); carries
  info to brain.
 Human brain divided into forebrain, midbrain,
  and hindbrain.
              Brain Structure
 Forebrain: cerebrum right and left hemispheres
  (center of intelligence) connected by corpus
  callosum; thalamus (relay station);
  hypothalamus (regulates heart rate, bp, temp,
  and pituitary hormones).
 Hindbrain: medulla (controls heart and
  breathing); cerebellum (balance and
  coordination); pons (connects cerebellum to
  cerebrum).
         Nervous system cells
 1. Neurons – nerve cells made up of
  dendrites (receive signals), cell body
  (contains organelles), and axons (carries
  signals away from cell body).
 a. Sensory neurons gather sensory info.
 b. Motor neurons carry out action signals.
 c. Interneurons integrate input and
  output.
 Synapses “connect” neurons by electrical
  or chemical means (neurotransmitters).
       Nervous system cells cont.
 2. Supporting cells -- help neurons
  function; 10-50 times more than
  neurons.
 a. Glial cells found in CNS; form
  blood-brain barrier and myelin
  sheath.
 b. Schwann cells found in PNS; form
  myelin sheath.
              Nerve Impulse
 Nerve impulses are electrical signals.
 Depends on flow of electrons across the
  neuron’s cell membrane.
 Neuron at rest has higher numbers of Na+
  outside, higher number of K+ inside, and high
  numbers of Cl- outside.
 Membrane potential is about –70 mV.
 Sodium-potassium pump keeps ions in these
  concentrations so neuron can be ready to fire.
            Nerve impulse cont.
   Electrical stimulus at the dendrites causes a shift
    in the ion balance as Na+ enters the cell
    (depolarization).
   When membrane potential rises +15-20 mV, the
    action potential is triggered.
   Na+ continues into the cell and K+ exits the cell
    as protein channels open (more depolarization);
    total +100 mV change.
   Action potential moves like a wave down the
    axon to the end of the cell.
   Membrane proteins will then reset the Na+/K+
    balance.
             Animations
 Nerve impulse http://highered.mcgraw-
  hill.com/sites/0072495855/student_view0/
  chapter14/animation__the_nerve_impulse.
  html
 Synapse
  http://www.mind.ilstu.edu/flash/synapse_
  1.swf

				
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posted:8/26/2011
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