Homework 1

Q) for question 2, saying the cell membrane hyperpolarizes means that the cell is becoming more negative right? because repolarizing means that the cell is becoming more negative, BUT had to depolarize first.   

A) Hyperpolarizes means that the difference between the ECF and ICF is becoming larger than at rest. So if the cell is already negative, then when it hyperpolarizes it becomes more negative.

After a cell depolarizes (the difference between ICF and ECF became smaller, went towards 0) the cell must "repolarize" meaning that it must build up its normal charge difference between the ICF and ECF (this is done with the Na/K pump). 

This is the way I think of this concept:

Lets pretend that the ECF and the ICF are the two poles on a magnet. As you know, a magnet is polarized and has a positive end and a negative end. There is a difference in the charges of the two poles.

If the magnet was hyperpolarized, that would mean that the two poles would have much stronger charges than normal (hyper= increase). The positive pole would become more positive and the negative pole more negative. Thus the charge difference between the two poles would become much larger than the original magnet. This magnet would become super strong.

If the same magnet was depolarized, that would mean that the two poles would have much weaker charges than normal (de=less). The positive pole would become less positive and the negative pole less negative. Thus the charge difference between the two poles would become much less than the original magnet and the magnet's strength would be very weak. The charge difference between the two poles of the magnet could even become 0 and the magnet would not be a magnet anymore, just a neutrally charged blob of metal.

If you were to repolarize that weak, depolarized magnet, that would mean that you are adding charge to the poles, making the charges at the poles stronger. Repolarize means that you will restore the charges of the two poles (and the difference in charge between the two poles) to the way it was originally, thus bringing the magnet back to its original strength. 

So that's how I remember what the words polarize, depolarize, hyperpolarize, and repolarize mean.  When thinking about cells specifically, think more about the difference of the charges between the ICF and the ECF, and not so much about which one is negative and which is positive (since the ECF is always set to 0).