1.4 Action Potentials Flashcards
What are neurons specialized for?
conduction electrical impulses known as action potentials
What creates an action potential?
movement of unequally distributed ions on either side of an axons plasma membrane
What is the plasma said to be at rest in a neuron?
polarized
What does it mean for a plasma membrane to be polarized?
one side has a different charge than the other side
What is it called when an axon is not conducting an impulse?
resting potential
What is the resting potential of a neuron?
-70mV
What does it mean that a neurons resting potential is -70mV?
charge on the inside of the cell membrane is 70 mV LESS than the outside of the membrane
What maintains the resting membrane potential?
sodium potassium pump
How does the sodium potassium pump work?
pumps out three sodium ions
pumps in two potassium ions
Why is the resting membrane potential negative?
plasma membrane is more permeable to potassium ions to flow back out of the cell and more sodium ions are pumped out than potassium ions pumped in
When does the resting potential become an action potential?
when the membrane becomes depolarized
What are the two main phases of an action potential?
depolarization
repolarization
What is depolarization?
membrane potential becomes more positive; inside is more positive than the outside
What is repolarization?
potential returns to resting state
What are the two important gates in an action potential?
sodium gate
potassium gate
What are the four phases of an action potential?
- resting potential
- depolarization
- repolarization
- afterpolarization
What is occuring during the resting potential phase?
sodium and potassium gates are closed
What is occuring during the depolarization phase?
sodium gates open causing influx of sodium and voltage travels up to +40mV
What is occuring during the repolarization phase?
sodium gates close, potassium gates open allowing outflux of potassium and potential returns to negative
What is occuring during the afterpolarization phase?
potassium gates slowly close; voltage drops below -70mV and then returns to resting
