I am studying for an exam and there is something I can't seem to understand. My textbook says that the endolymph contains 150mM potassium, 2mM Na+ and 130mM Cl-. The perilymph contains 5mM potassium, 140mM Na+ and 110mM Cl-. "Thus" the electric potential between perilymph and endolymph is +80mV (endolymph being positive).

I can see that there are chemical gradients but why is the endolymph so much more positively charged than the perilymph?

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    $\begingroup$ Homework questions are off-topic on Biology unless you have shown your attempt at an answer. For more information see our homework policy. $\endgroup$ – MattDMo Aug 25 '16 at 22:10
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    $\begingroup$ Marina - @MattDMO is right that you should provide more information. Most importantly, are you referring referring to 'why' (functional aspect to the workings of the inner ear) or to the 'how' (mathematical underpinnings of membrane potentials). If the latter, you should find your answer in this site - there have been many questions on potential differences and their mathematical grounds (search for Nernst or Goldman equations). If the former, then it would be a more interesting question imo. Either way, try to edit your question to make it specific where the bottleneck is. $\endgroup$ – AliceD Aug 26 '16 at 8:51