1. Pick the correct answer and 2. Write a short explanation Out Na+ 120 mM IN K+ 5 mM Na+ K+ 12 mM 125 mM Cl 125 mM Cl- 5 mM A-1.2 108 mM Assume: 1. Membrane is permeable to Na+ and K+ but not to Cl- 2. b = 0.02 If the membrane becomes permeable to Cl-, the membrane potential would.... a) Depolarize b) Hyperpolarize c) Stay the same

Under what conditions could the opening of a chloride channel actually depolarize a neuron rather than hyperpolarize it? i. The neuron is resting at -75 mV ii. The extracellular chloride concentration is lower than the intracellular chloride concentration iii. The neuron is close to its threshold of -55 mV O a. i only O b. ii only O c. i and ii only O d. ii and iii only O e. i, ii, and i O f. None of these

9. You are performing an experiment at with an artificial membrane (i.e not a living cell). You place a NaCl solution on each side of the membrane. You discover that if you place a 10-fold NaCl concentration gradient across this membrane (higher NaCl concentration outside than inside) you initially see a +20 mV membrane potential develop. If the Cl permeability is assigned a value of 1, what value would you assign to the Na" permeability? Assume 2.3RT/F = 60 mV.

9. If sodium permeability (Pna) increases compared to normal, what is the effect on the membrane potential? (determine: change in charge on the inside of the membrane and polarity)

35.Given the following table, calculate the Resting Membrane Potential (in mV, rounded to the nearest tenths), using the GHK equation. Ion [Outside] mM [Inside] mM Relative Permeability at Rest Nernst Potential (mV) K+ 4 130 1.0 -110.2 Na+ 130 5 0.04 67.4 Cl- 75 5 0.45 -97.5