6.021/Notes/2006-10-18

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Electrical properties of cells

  • Information processing
    • code sensory inputs
    • generate outputs
    • computation
  • Graded potential vs action potential
    • Graded: change in input leads to change in output
      • Doesn't have to be linear, just incremental
      • Many inputs cause graded change in potential
      • All cells do graded potentials
    • Action potential
      • Incremental change leads to different response
      • Neurons/electrical cells
  • Properties of action potentials
    • All-or-none
    • threshold
    • refractory
      • absolute refractory period: essentially impossible to generate action potential
      • relative refractory period: requires stronger stimulus (higher threshold)
      • also a period where threshold is lower (more easily excitable)
    • Strength/duration
    • Accomodation
      • with slow enough change, doesn't cause action potential even after it goes above threshold
    • Anode break
      • can trigger action potential by lowering potential for awhile then raising to rest potential
    • decrement-free
      • can't think of neurons as a wire which degrades a signal
      • neurons have decrement-free conduction
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