6.021/Notes/2006-10-18

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