Nerve Conduction

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Nerve Conduction

• SC.912.L.14.22

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Essential Question

• How are nerve impulses generated?

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At Rest

• In the cytosol and interstitial fluid there are
  ions (charged particles) like Na and Cl-.
• Most ions cross the plasma membrane at specific
  ion channels. The rate that ions diffuse across
  a membrane depends on the number of channels they
  can use.
• Channels and active transport pumps are set up so
  that there is a greater negative charge on the
  inner side of the membrane.

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Resting Potential
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When stimulated

• One type of ion channel is a voltage gated
  channel.
• When the electrical stimulus is strong enough the
  channel quickly opens and rush across the plasma
  membrane making the inside positive.
  (Depolarization)
• The channel quickly closes and things return to
  the resting state. (Repolarization)

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• Depolarization and Repolarization take about
  1/1000 of a second.

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Conduction

• Once a nerve impulse is initiated its speed of
  travel is determined by the type of nerve.
• If the nerve is myelinated the current moves in
  jumps called saltatory conduction.
• If the nerve is unmyelinated the current travels
  across each portion of membrane.
• Notice the time differences in the next slide.

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Conduction of Nerve Impulses
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At the synapse

• The neurons are separated by the synaptic cleft.
• Depolarization at the synapse causes the opening
  of Ca2 channels. The calcium ions stimulate the
  release of neurotransmitters.
• Neurotransmitter molecules diffuse across the
  synaptic cleft and initiate depolarization at the
  next neuron.

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The Synapse
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Vocabulary

• Membrane Potential
• Resting Potential
• Gradient
• Action Potential
• Myelin
• Neurotransmitter
• Saltatory Conduction
• Continuous Conduction
• Synapse
• Synaptic Cleft

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Neuroscience Activities

• http//faculty.washington.edu/chudler/outside.html