Electrophysiology question

[dudewtf]

I'm reviewing for an exam and ran across a question that has me rather stumped. I tried simply applying the Nernst equation but it seems I'm still missing something importantn

"An electrically excitable cell with a resting potential of -70mV the following conditions are present (temperature is 37°C):

Intracellulär Extracellular
K+ 160nM 5mM
Na+ 20nM 140mM
Cl- 10nM 120mM
Ca2+ 100mM 1mM

1. When the cell depolarisering [Ca2+] rises to 15uM, while the membrane potential reaches +61mV. Under these conditions , would Ca2+ move Into or out of the cell?

2. Which way would Na+ move?

3. Which way would K+ move if Na+ were allowed to dominate?

 

The above is my translation! Let me know if something is unclear.

Now, my problem is mainly question number 3, I honestly have no idea how to approac this. I've tried asking friends as well and the don't really understand how to answer that either.

 

EDIT: Edited for clarity

Edited August 17, 2016 by dudewtf

[dudewtf]

Please, I really need help with this!

[Function]

Nederlandstalig? Je bent "depolarisering" vergeten te vertalen. Herexamen?

 

Not really on-topic but in English: should be moved to homework section.

 

On-topic and in English: question 1 already doesn't make sense.

However, I must note that the answer on these questions can't be given so easily: it all depends on the state of the N, K and Ca channels, of which a lot their closure/opening depends on the cell membrane potential, e.g. Ca-channels tend to open more after a depolarization, allowing for a Ca-influx into your cell, making it possible for Ca to bind to synaptotagmin (I'm not very sure anymore about this, but it's what remained in my mind) and allow for vesicle ejection

 

Do you know the phenomenon of "action potentials"? You should know what happens to Na, K and Ca channels in function of the cell membrane potential. That is undeniably important in understanding the genesis of action potentials. I need you to look up a few things: Na channels and their m- and h-gates; K channels and their n-gates; voltage dependent/voltage gated Ca-channels; action potentials; open probability (Po).

 

The third question sounds like a question that'd sound from my very professor in physiology. Say no more if his name starts with an L (please do tell me if it does ).

If Na were allowed to dominate, what would happen to the cell's membrane potential? If not considering K-channels and their n-gates, what would you expect to K-ions, thinking very logically? Then considering K-channels and their n-gates, what would happen?

Edited September 2, 2016 by Function