potentials leading to muscle activation. In this problem we'll explore that phenomenon by developing a model to understand the process. Soy sauce contains sodium chloride (i.e. salt) at a high concentration. When soy sauce is poured on the squid tissue, the extracellular concentration of both sodium and chloride go up by equal amounts because one chloride ion dissolves for every sodium ion. Because the cell membrane is partially permeable to both chloride and sodium, eventually the intracellular concentrations of these ions will also increase. Before any soy sauce is poured on the squid, the concentrations of ions outside and inside the cell are [Na]out=145mM [K]out=4mM [Cl]out=[K]out+[Na]out25mM and the intracellular concentrations are [Na]in=15mM [K]in=150mM [Cl]in=[K]in+[Na]in156mM The expressions for chloride concentration recognize that chloride will move across the membrane to balance the charge from sodium and potassium ions so that the chloride concentration depends on the sodium and potassium concentrations 1. In Japan, squid is usually served cold at a temperature of about 10C. The relative permeabilities of squid axon cell membrane to potassium, sodium and chloride are 1,0.05 and 0.45 respectively. Develop a model of the dancing squid with the following behavior: - When the soy sauce is poured on the squid the extracellular concentration of sodium doubles and the concentration of chloride increases to maintain neutrality according to the formula for chloride concentration given above. These extracellular concentrations do not change further. - Over time, sodium and chloride flow into the cell in equal amounts (i.e. one mol of chloride for each mol of sodium). - The concentrations of potassium inside and outside the cell do not change. a) Make a plot of the membrane potential against intracellular sodium concentration as the intracellular sodium concentration increases. Show your work. [5 pts] b) If the threshold for action potential generation in the axon is +10mV above the initial resting level (i.e. the membrane potential of the squid axon before any soy sauce is poured), what are the ion concentrations inside and outside of the cell at the moment the squid starts to move? You may solve this question numerically. [4 pts]