12.4

• resting membrane potential

  • membrane potential of a resting cell
• graded potential

  • temporary, localized change in resting potential caused by a stimulus
• action potential

  • electrical impulse
  • produced by graded potential
  • propagates along surface of axon to synapse
• cytosol is negatively charged
• chemical gradients

  • concentration gradients of ions
  • electrical gradients
• electrochemical gradient

  • sum of chemical and electrical forces acting on an ion
  • form of potential energy
• equilibrium potential

  • membrane potential at which there is no net movement
• resting potential average is -70mV
• passive ion channels (leak channels)

  • always open
  • permeability changes with conditions
• active ion channels (gated ion channels)

  • open/closed based on stimuli
  • at resting membrane potential, most are closed
• chemically gated ion channels (ligand-gated ion channels)

  • active channel
  • opens when they bind with specific chemicals
  • cell body and dendrites of neurons
• voltage gated ion channels

  • active channel
  • responds to membrane potential changes
  • axons of neurons and sarcolemma of skeletal and cardiac muscle cells
• mechanically gated ion channels

  • active channel
  • responds to membrane distortion
  • sensory receptors
  • channels made of proteins