a) The action potential for a typical neuron is shown at the right. For this neuron, the sodium / potassium pump works continuously to set up the ion concentration gradients. Typically, the K* concentrations are high inside the neuron and the Nat concentrations are high outside of the cell. There are also leaky potassium channels that are always open. Which point on the membrane potential graph is specified by concentration gradients and the leaky K* channel? Why does the sign of the membrane potential at this point make sense? Membrane potential +50 (AW) O -50 -100 Action- potential Threshold 1 Resting potential Time 1 b) When a neuron first starts to receive signals, but before it reaches threshold, what happens to its membrane potential? What ion channels open? c) When the membrane potential rises rapidly, what ion channels open? Why does this positive change make sense? d) When the membrane potential falls rapidly, which ion channels open? Which ones are closed? Why does the negative membrane potential make sense?