Comments |
“In darkness Na+ ions enter the outer segment through channels in the surface membrane. The current loop is
completed by the outward movement of K+
ions from channels in the inner segment. The inner segment also expends
energy to pump Na+ out of the cell and K+ into the cell and thus maintain their concentration gradients. In darkness this circulating current produces a voltage difference of about -40mV between the inside and outside of the cell...In darkness, the circulating current, electromotive
forces across the cell membrane, and resistance of the membrane set a voltage difference of about –40 mV between the inside and outside of the cell.” |