rico11

It's a prep question for a test I have on Tuesday, so I want to make sure I have everything correct. My general thought is that everything will flow down the electrochemical gradient, but what effect will that have on ATPases? Would it be better for me to just disregard them and assume they'll be overwhelmed? For the higher EC [Na+], can I assume that too much Na+ will come in through ion channels and the ATPases/K+ leak channels won't be able to establish the correct -70 mV Vm? Or does the neuron have gated Na+ channels that won't let Na+ in? But I would assume since the outside would be even more positive, the channels would have to open to let more positive ions in the intracellular fluid. I feel like I know a lot about the neuron, but not enough to completely say what would happen in this situation. Any clarification?

Hey everyone, My question is, what would happen if you raised the extracellular potassium concentration for a neuron to be very large (like 220 mMol)? I believe it would cause an influx of K+ ions through the membrane and you'd end up getting a very positive charge inside the cell. What effect would that have on action potentials? Would they just stop then? I guess one AP would fire, then the cell would stay depolarized. What would this do to Na/K ATPase? Would it just stop as there is already a lot of K+ or would it keep going? Also, what would happen if you raised the extracellular Na+ concentration to very large (like 220 mMol)? I assume there would be less of a change because Na+ already has a large concentration outside the cell, but it may result in more K+ efflux to balance out the resting Vm, since there would be more positively charged ions outside the membrane. What would happen if you removed all Na+ from the extracellular fluid? Specifically, what would happen to Vm? I suppose action potentials would not occur because for an action potential to fully happen the cell needs Na+ to depolarize the cell to around +30 (I believe?) And I would think K+ would leak out, going down the electrochemical gradient, which is stronger due to the absence of Na+. I'm confused with what that would do to the Vm though. Wouldn't it eventually flow to an equilibrium, or no? Please help, I've got ideas, but I need some clarification and help to understand this.

Okay, so thermogenin (UCP1) increases heat production, but how does it changed the ATP produced per oxygen used and how does it change the amount of ATP made per mole of a given fuel? I believe that thermogenin just imports H+ atoms back into the matrix and lowers the H+ gradient in the mitochondria. So I would think the rate that ATP synthase would be slowed by a weaker H+ gradient, which would in turn, reduce the rate of ATP production, but wouldn't change the efficiency of the production (it would make it slower, but make just as much ATP with the same input). Can anyone clarify for me? Thanks! -Ricardo

Hi everybody! I was wondering, if performing an experiment to measure metabolic heat production with varying temps from -20 to 50 degrees C in a mammal, what would be the effect if you shaved off its fur? Would convective forces play a larger role even if there is no wind? Would the lower critical limit have a greater slope after shaving the fur off? Or would the lower critical limit just occur at a higher temp (rather than 10 C it occurs at 20 C)? Because there is no wind, I'm wondering if the ambient temperature would cause a steeper slope in the lower critical limit, or if the slope would only be steeper once applying wind. Thanks!