Resting & Action Potential

Hello all,
can anyone help explain (in simple terms) the resting and action potention in nerves to me? every books explains different and im getting so confused with what gates are open and which way the ions are going at every point. ahh, can anyone be kind enough to explain??
:suith:

Reply 1

Comp_Genius

The books are probably 'wrong' if they are A-level ones. The sodium potassium pump does not really contribute to the RP of neurones that much.
Resting potential is the potential when there isn't an action potential propagating; this is established by high concentration gradient and high permeabliity of the cell membrane of the axon to K+, K+ moves out.

Depolarisation occurs, by sodium entry, and this causes an electric potential difference across the membrane, to which sodium-channels are sensitive. At a threshold more sodium comes into the cell causing an action potential.

Reply 2

Cirsium

Voila - as simple as I can

Nerve impulse transmission.doc71.2KB

Reply 3

WokSz

Right in simple terms: (I'm typing this up as it helps my revision too :smile:

: )

Resting Potential
- 3 NA+ is actively pumped out, and 2 K+ is pumped in by the Sodium Potassium pump.
- Also, the membrane of the axon is more 'leaky' to K+ than Na+, so K+ moves out faster, causing a membrane potential of -65mV. This basically means, that the inside of the membrane is 65 mV more negative, than the outside.

Action Potential
- a nerve impulse arrives, which causes Na+ channels to open. This causes an influx of Na+, depolarising the membrane. This causes the action potential.
- Na+ depolarises till +40mV, and the Na+ channels then close.
- K+ channels will now open, causing an outflux of K+, repolarising the membrane.
-The Membrane repolarises so much, that it actually increases by more than the original value (-65mV)
-The k+ channels will close, and the Sodium Potassium pump will restore the resting potential.