Ion Channels of Excitable Membranes ? ? electrochemical gra-

di- ent NaCl Na^{+} Cl^{−} KCl CaCl_{2}

K^{+} Cl^{−} Ca^{2+} nM ? ?? Na^{+} K^{+} Cl^{−} Ca^{2+} Na^{+}/K^{+}−

AT P ase Na^{+} K^{+} ? Na^{+}−

Ca^{2+} Na^{+} Ca^{2+} Na^{+} Ca^{2+} Na^{+} Na^{+} Ca^{2+} against

10^{8} ? permeability

C I A G R S Ω V V = IR. (1)

V = IG. (2)

S G S I_{S} S V driv- ing

force

Na^{+} K^{+} S S S I_{S} = G_{S}(DrivingF orce_{S}).

(3)

V_{m} E_{S} ?? S

DrivingF orce_{S} = (V_{m}−E_{S}). (4)

I_{S} = G_{S}(V_{m}−E_{S}). (5)

??

E_{m} = \frac{RT}{F} ln\frac{P_{K}[K]_{e} + P_{Na}[Na]_{e} + P_{Cl}[Cl]_{i}}{P_{K}[K]_{i} + P_{Na}[Na]_{i} + P_{Cl}[Cl]_{e}} ,

(6)

E_{m} P_{S} S ?

\begin{matrix}F & 9.6485 × 10^{4} & Cmol^{−1} \\ T (K) & 273.15 & ^{∘}Celcius \\ R & 8.3145 & V Cmol^{−1}K^{−1} \end{matrix}

? ? ? ? ? ? Na^{+} K^{+} Na^{+} ? ? ?? Are rate constants constant? ? ? Ca^{+2} ? ? ? ?