The following data were obtained from the cells of a frog. Ion Intracellular Con

Question

The following data were obtained from the cells of a frog. Ion Intracellular Conc. (mM)Extracellular Conc. (mM) Permeability at Rest 150 18 4 87 400 Na CI Proteins 160 110 392 7. Depolarizations (APs) are possible because of the huge amount of stored potential energy (in the dCNa on both sides of the membrane) between Vm and the ENa, set by Gibb-Donnan, which is then released as kinetic energy. Prove mathematically that during the depolarization of the action potential, Vm ENa+ Le., show that the difference between Nalo and Nah is relatively small at the peak of the action potential, where the ENa -30 m V and the resting membrane potential (V)-70 mV. Remember that at this point in the action potential, the influence of K is negligible (5)

Explanation / Answer

At the peak of the action potential ENa+ = 30mV

Resting membrane potential Vm =-70mV

At the peak of the action potential, the membranes are fully permeable to the Na+ ions because of all the Na+ gates are open. Due to this increase in the permeability to the Na+ ions the concentration of the ion reaches equilibrium on both the sides of the membrane and thus, Vmis nearly equal to the ENa+

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