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Table I.

Summary of physical and electrophysiological parameters used

Symbol Description Value Reference 
Physical parameters 
Am Surface membrane area 769231 cm2 l−1 
At t-System membrane area 3076924 cm2 l−1 
Vt Relative t-system volume 3.2e-3 liter.l−1 2, 7 
Cm Membrane capacitance 1e-6 F cm−2 
Ra t-System access resistance 72.3 Ω cm2 
Ri Longitudinal fiber resistance 180 Ω cm 
gt t-System luminal conductance 3.7e-3 S cm−1 
σt t-System tortuosity factor 0.21 
Electrophysiological parameters 
Ns Na+/K+-ATPase sarcolemmal density 9e-12 cm−2 
Nt Na+/K+-ATPase tubular membrane density 4.5e-12 cm−2 
PNa Background Na+ permeability 2.16e-8 cm s−1 4, 5 
PK Background K+ permeability 6.3e-7 cm s−1 4, 6 
PCl Background Cl- permeability 2.7e-6 cm s−1 4, 6 
PNa(v,s) Voltage-gated Na+ channel sarcolemmal permeability 0.00265 cm s−1 
PNa(v,t) Voltage-gated Na+ channel t-system permeability 0.00034 cm s−1 
PK(v,s) Voltage-gated K+ channel sarcolemmal permeability 0.0004 cm s−1 
PK(v,s) Voltage-gated K+ channel t-system permeability 0.0001 cm s−1 
Symbol Description Value Reference 
Physical parameters 
Am Surface membrane area 769231 cm2 l−1 
At t-System membrane area 3076924 cm2 l−1 
Vt Relative t-system volume 3.2e-3 liter.l−1 2, 7 
Cm Membrane capacitance 1e-6 F cm−2 
Ra t-System access resistance 72.3 Ω cm2 
Ri Longitudinal fiber resistance 180 Ω cm 
gt t-System luminal conductance 3.7e-3 S cm−1 
σt t-System tortuosity factor 0.21 
Electrophysiological parameters 
Ns Na+/K+-ATPase sarcolemmal density 9e-12 cm−2 
Nt Na+/K+-ATPase tubular membrane density 4.5e-12 cm−2 
PNa Background Na+ permeability 2.16e-8 cm s−1 4, 5 
PK Background K+ permeability 6.3e-7 cm s−1 4, 6 
PCl Background Cl- permeability 2.7e-6 cm s−1 4, 6 
PNa(v,s) Voltage-gated Na+ channel sarcolemmal permeability 0.00265 cm s−1 
PNa(v,t) Voltage-gated Na+ channel t-system permeability 0.00034 cm s−1 
PK(v,s) Voltage-gated K+ channel sarcolemmal permeability 0.0004 cm s−1 
PK(v,s) Voltage-gated K+ channel t-system permeability 0.0001 cm s−1 

References: 1, Pedersen et al., 2011; 2, Wallinga et al., 1999; 3, model derived to maintain [Na+]i in physiological range; 4, total conductance taken from Pedersen et al. (2011); 5, PCl/PK ratio (Dulhunty, 1979; Pedersen et al., 2005); 6, PNa/PK ratio model derived to obtain membrane potentials in agreement with control experiments; 7, Henneberg and Roberge, 1997. Hodgkin-Huxley parameters for voltage-gated Na+ and K+ channels are from Henneberg and Roberge (1997). Note that all intracellular ion concentrations and compartmental volumes in the model are variables, the values of which are determined solely by the choice of parameters, as demonstrated in Fig. 2. Extracellular Na+ and K+ concentrations matched those of the experimental studies, and extracellular [Cl] was chosen to make the solution electroneutral.

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