Lecture 2 Notes

by Reads (690)

Normal Physiological Concentrations of IONS:

                   Inside  axon        Outside axon    Na+                 15 mM                  150 mM    K+                 100 mM                    5 mM    Cl-                 13 mM                  150 mM    Ca++                 0.0002 mM               2 mM    proteins (A-)      400 mM                    –    

II. If the problem involves CHANGING THE ION CONCENTRATIONS INSIDE OR OUTSIDE OF THE CELL
from the normal physiological concentrations to some other value, you MUST figure out how that changes the Eq for that ion. To get the new Eq, use the simplified Nernst equations above. You will find, by plugging in different numbers for the concentrations INSIDE and OUTSIDE, that the following is true:

K+:        Changes from normal will greatly affect Vm of resting cell.        add more K+ outside           or                ———->  makes Eq K+ LESS NEGATIVE    decrease K+ inside cell               than -80 mV         —————————————————–    decrease K+ outside           or                ———->  makes Eq K+ MORE NEGATIVE    increase inside K+                    than -80 mV        Na+:        Changes from normal will affect Vm ONLY if channels are OPEN!        add more Na+ outside           or                ———->  makes Eq Na+ MORE POSITIVE    decrease Na+ inside                   than +62 mV         —————————————————-    decrease Na+ outside          or                 ———->  makes Eq Na+ MORE NEGATIVE    increase Na+ inside                   than +62 mV        Cl-:        Changes from normal will affect Vm ONLY if channels are open.        add more Cl- outside          or                 ———–>  makes Eq Cl- MORE NEGATIVE    decrease Cl- inside                    than -65 mV        —————————————————–    decrease outside Cl-          or                 ———–>  makes Eq Cl- MORE POSITIVE    increase Cl- inside                    than -65 mV    

Note:
add, increase, decrease, etc. means adding or reducing compared to the normal physiological concentrations of the ion.

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