AVS 271 Anatomy and Physiology

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AVS 271 Anatomy and Physiology

• Handout 8
• September 26, 2008
• Nervous System
• Chapter 8
• (Start of material for exam 2 however,
  the material in Handout 7 on chemical
  synapses and the movie on neural activity
  will also be covered on exam 2)

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Nervous System
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Membrane Potential

• All cells have an electrical potential
  (charge difference) across their plasma
  membranes oriented with the inside of the
  cell negatively charged with respect to the
  outside.

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Resting Membrane Potential
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Magnitude of Resting Membrane Potential is
Determined by

• Differences of specific ion concentrations
  in the intra and extra cellular fluid
• Sodium and potassium most important
• Differences in membrane permeability to the
  different ions
• Ion channels

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Generation of Different Ion
ConcentrationsInside vs. Outside of Cell
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Sodium Potassium ATPase Pump
Electrogenic Pump
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Differences in Membrane Ion Permeability

• Ligand sensitive channels
• Voltage gated channels
• Mechano sensitive channels

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At rest, the plasma membrane is 50 to 75
times more permeable to potassium compared
to sodium
K
Resting Membrane Potential
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Resting Membrane Potential

• Transient changes in the resting membrane
  potential produce electric signals
• The most important way neurons process and
  transmit information
• Two forms of electric signals
• Graded potentials
• Action potentials

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Terminology Changes in Membrane Potential

• Depolarize
• Overshoot
• Repolarize
• Hyperpolarize

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