Question

Look at your data and find the mean membrane potential value that you obtained from muscle fibers bathed is a solution with a sodium concentration of 200 mEq/L - this is the concentration in normal crayfish saline. If threshold is 15 to 20 mV more depolarized than this value, what would have to happen to the external sodium concentration to depolarize the membrane to threshold?

*The mean membrane potential value that we obtained for the muscle fibers bathed in a 200mEq/L solution was -65.4mV

Answer 1

Depolarizing the membrane because of a stimulus help the cell to depolarize from -70 mV to -55 mV.The membrane reaches that voltage, the voltage-gated Na+ channels open.Depolarization that does not change the membrane potential to -55 mV or higher will not reach threshold and thus no action potential is generated. Any stimulus that depolarizes the membrane to -55 mV or beyond will cause a large number of channels to open and action potential will be initiated.The change in the membrane voltage from -70 mV at rest to +30 mV at the end of depolarization is a 100-mV change .The cell to depolarize from -70 mV to -55 mV.Once membrane reaches voltage, and causes Na+ ions to open is called threshold,depolarization that does not change the membrane potential to -55 mV or higher will not reach threshold and thus no action potential is generated,stimulus that depolarizes to -55 mV or beyond will cause a large number of channels to open and an action potential will be initiated.