14 terms

Action potential

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all or nothing response
A neuron either reaches threshold and generates an action potential or not. Action potentials are always the same size.
action potential
A momentary reversal in electrical potential across the membrane of a neurone that occurs when the cell has been activated by a stimulus.
threshold
The level of stimulation required to trigger an impulse in a neurone.
depolarisation
The change from a negative resting potential to a positive action potential (caused by opening of sodium channels).
repolarisation
The change from a positive potential difference back to a negative resting potential (caused by opening of potassium channels).
hyperpolarisation
When resting potential is restored too many potassium ions may diffuse out of the cell (it overshoots) which causes the potential difference to be slightly lower than usual.
refractory period
The period following an action potential, in which another action potential cannot be generated. This means action potentials are unidirectional and allows the cell to restore ions on the correct side of the membrane.
sodium-potassium pumps
pump positive ions out from the inside of the neuron, making them ready for another action potential
intensity
level of action potential remains the same, throughout the length of the axon
all or none
referring to the fact that a neuron either fires completely or does not fire at all
sodium channel
a protein channel in the nerve cell membrane that controls the movement of sodium ions into the cell
potassium channel
leak channel - remains open
saltatory conduction
the rapid skipping of an action potential from node to node on myelinated neurons
resting membrane potential
-70 mV
a difference in electrical potential across the membrane of a nerve cell during an inactive period