<Li> g is the total conductance of all permeant ions, in this case g + g + g </Li> <P> For determination of membrane potentials, the two most important types of membrane ion transport proteins are ion channels and ion transporters . Ion channel proteins create paths across cell membranes through which ions can passively diffuse without direct expenditure of metabolic energy . They have selectivity for certain ions, thus, there are potassium -, chloride -, and sodium - selective ion channels . Different cells and even different parts of one cell (dendrites, cell bodies, nodes of Ranvier) will have different amounts of various ion transport proteins . Typically, the amount of certain potassium channels is most important for control of the resting potential (see below). Some ion pumps such as the Na+ / K+ - ATPase are electrogenic, that is, they produce charge imbalance across the cell membrane and can also contribute directly to the membrane potential . Most pumps use metabolic energy (ATP) to function . </P> <P> For most animal cells potassium ions (K) are the most important for the resting potential . Due to the active transport of potassium ions, the concentration of potassium is higher inside cells than outside . Most cells have potassium - selective ion channel proteins that remain open all the time . There will be net movement of positively charged potassium ions through these potassium channels with a resulting accumulation of excess negative charge inside of the cell . The outward movement of positively charged potassium ions is due to random molecular motion (diffusion) and continues until enough excess negative charge accumulates inside the cell to form a membrane potential which can balance the difference in concentration of potassium between inside and outside the cell . "Balance" means that the electrical force (potential) that results from the build - up of ionic charge, and which impedes outward diffusion, increases until it is equal in magnitude but opposite in direction to the tendency for outward diffusive movement of potassium . This balance point is an equilibrium potential as the net transmembrane flux (or current) of K is zero . A good approximation for the equilibrium potential of a given ion only needs the concentrations on either side of the membrane and the temperature . It can be calculated using the Nernst equation: </P> <Dl> <Dd> E e q, K + = R T z F ln ⁡ (K +) o (K +) i, (\ displaystyle E_ (eq, K ^ (+)) = (\ frac (RT) (zF)) \ ln (\ frac ((K ^ (+)) _ (o)) ((K ^ (+)) _ (i))),) </Dd> </Dl>

What is an increase in a cell's membrane potential