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I was reading a physio book at got confused about one part of potentials. I want to start off by saying that anything with a charge has never been my forte (be it chem or physics) so I appreciate anything anyone can offer that would englighten me!
According to the text "increasing extracellular cation concentration causes a more positive potential; this is called depolarization, since the normal membrane potential is negrative. Decreasing extracellular concentration causes a more negative potential; this is called hyperpolarization."
My first rxn to this was "if intracellular is normally more negative than extracellular, then wouldn't dumping more + outside make the cell even more negative relatively? and isn't this hyperpolarization?"
The book goes on to say increasing K+ or Na+ concentration outside will depolarize the cell while decreasing K+ or Na+ concentration outside will hyperpolarize the cell. This seems to play off the above statement - which confuses me.
However, the book says changing the conductances of these ions has opposite effects (that part I get - if K+ conductance increases, K+ will leave the cell, cell becomes more negative/hyperpolarized - where increasing Na+ conductance --> Na+ enters the cell, cell becomes less negative = depolarized).
So I guess my confusion lies in this changing the extracellular milleu of ions and why that has the effect it does on the cell.... Thanks in advance for any help!!!
According to the text "increasing extracellular cation concentration causes a more positive potential; this is called depolarization, since the normal membrane potential is negrative. Decreasing extracellular concentration causes a more negative potential; this is called hyperpolarization."
My first rxn to this was "if intracellular is normally more negative than extracellular, then wouldn't dumping more + outside make the cell even more negative relatively? and isn't this hyperpolarization?"
The book goes on to say increasing K+ or Na+ concentration outside will depolarize the cell while decreasing K+ or Na+ concentration outside will hyperpolarize the cell. This seems to play off the above statement - which confuses me.
However, the book says changing the conductances of these ions has opposite effects (that part I get - if K+ conductance increases, K+ will leave the cell, cell becomes more negative/hyperpolarized - where increasing Na+ conductance --> Na+ enters the cell, cell becomes less negative = depolarized).
So I guess my confusion lies in this changing the extracellular milleu of ions and why that has the effect it does on the cell.... Thanks in advance for any help!!!