L67- Action potential Flashcards
is the inside of a cell negative or positive?
negative = -70mV
why is the resting membrane potential the number it is?
due to unequal distribution of ions across a selectively permeable membrane
what ion moves out the cell and what ion moves in in the cell?
out- Na+
in- K+
The resting cell membrane has a high permeability to what?
K+
What does depolarisation mean?
the membrane potential becomes more positive than the resting potential
what does repolarisation mean?
when the membrane potential GOES BACK DOWN TO RESTING POTENTIAL
what does hyperpolarisation mean?
when the membrane potential becomes more negative than the resting potential
what happens during a action potential?
- Resting membrane potential - membrane permeable to K+
- depolarization to the threshold potential
- rapid depolarization due to activation of voltage-gated Na+ channels - Na+ moves down its electrochemical gradient
- peak of action potential (approx +40mV)
- Voltage-gated K+ channels open causing repolarization
- afterhyperpolarization
- resting membrane potential is restored
- (The NaK-ATPase restores the concentration gradients back to original levels)
what doe voltage gated ion channels do?
open to allow ions in and out
what is the absolute refractory period?
the period immediately following stimulation when the neutron can be restimulated to produce an action potential, Na+ channels are inactive
what is the relative refractory period?
when greater stimulation is required to trigger action potential, K+ channels still activated
what does conduction velocity depend on?
- diameter of the axon
- myelination
what is saltatory conduction?
in myelinated nerves the action potential passes from node to node, it increases speed
what happens when the action potential reaches the nerve terminal (synapse)?
it triggers the release of a transmitter
