1.   a.  Graph a neuronal action potential in a normal patient.  Label the axes, ion channels opening and closing, ion fluxes and resting membrane potential.

 b. The kidneys are critical for secreting potassium and maintaining normal potassium concentrations in the blood.  A patient with failing kidneys may be hyperkalemic (elevated blood potassium). Elevated plasma potassium causes cells to become less polarized. Show on the graph above the relative resting membrane potential in a hyperkalemic individual.

 c.  In the hyperkalemic individual, would the resting membrane potential be the same distance from threshold potential, closer to threshold or further from threshold?

 d.  What would you expect in terms of muscle tone in the hyperkalemic individual i.e. no change, flaccid, or twitchy

2.  What are 2 key differences in transmembrane transport between diffusion and active transport? Be brief.

3.  You discover a new unicellular organism and begin to study its physiology.

 a.  You determine that its membrane composition is typical of a mammalian cell.  What kind of molecules form the bilayer--describe the molecules and their specific orientation in relation to the extracellular and intracellular fluid environments.  A drawing with labels would be adequate.

 b.  You already know that water diffuses readily across your creature’s membrane.  You place your creature in a dish of hypertonic saline and note that the creature starts to shrivel.  What can you surmise about: 1) water diffusion across the membrane; 2) movement of sodium across the membrane.