Figure 12.20. Ion gradients and resting membrane potential of the giant squid axon.

Figure 12.20Ion gradients and resting membrane potential of the giant squid axon

Only the concentrations of Na+ and K+ are shown, because these are the ions that function in the transmission of nerve impulses. Na+ is pumped out of the cell while K+ is pumped in, so the concentration of Na+ is higher outside than inside of the axon, whereas the concentration of K+ is higher inside than out. The resting membrane is more permeable to K+ than to Na+ or other ions because it contains open K+ channels. The flow of K+ through these channels makes the major contribution to the resting membrane potential of -60 mV, which is therefore close to the K+ equilibrium potential.

From: Transport of Small Molecules

Cover of The Cell
The Cell: A Molecular Approach. 2nd edition.
Cooper GM.
Sunderland (MA): Sinauer Associates; 2000.
Copyright © 2000, Geoffrey M Cooper.

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