def model sodium_ion_channel as
   def import using "Noble62_units.xml" for
      unit mV using unit mV;
      unit ms using unit ms;
      unit mM using unit mM;
      unit per_ms using unit per_ms;
      unit per_mV using unit per_mV;
      unit per_mV_ms using unit per_mV_ms;
      unit microS using unit microS;
      unit nanoA using unit nanoA;
   enddef;
   def group as encapsulation for
      comp sodium_channel incl
      comp sodium_channel_m_gate;
      comp sodium_channel_h_gate;
   endcomp;
   enddef;
   def comp sodium_channel as
      var V: mV {pub: in, priv: out};
      var t: ms {pub: in, priv: out};
      var g_Na_max: microS {init: 400000};
      var g_Na: microS;
      var E_Na: mV;
      var m: dimensionless {priv: in};
      var h: dimensionless {priv: in};
      var Nai: mM {pub: in};
      var Nao: mM {pub: in};
      var RTF: mV {init: 25};
      var i_Na: nanoA {pub: out};
      E_Na = RTF*ln(Nao/Nai);
      g_Na = pow(m, 3{dimensionless})*h*g_Na_max;
      i_Na = (g_Na+140{microS})*(V-E_Na);
   enddef;
   def comp sodium_channel_m_gate as
      var V: mV {pub: in};
      var t: ms {pub: in};
      var m: dimensionless {init: 0.01, pub: out};
      var alpha_m: per_ms;
      var beta_m: per_ms;
      alpha_m = -0.10{per_mV_ms}*(V+48{mV})
        /(exp(-(V+48{mV})/15{mV})-1{dimensionless});
      beta_m = 0.12{per_mV_ms}*(V+8{mV})
        /(exp((V+8{mV})/5{mV})-1{dimensionless});
      ode(m, t)=alpha_m*(1{dimensionless}-m)-beta_m*m;
   enddef;
   def comp sodium_channel_h_gate as
      var V: mV {pub: in};
      var t: ms {pub: in};
      var h: dimensionless {init: 0.8, pub: out};
      var alpha_h: per_ms;
      var beta_h: per_ms;
      alpha_h = 0.17{per_ms}*exp(-(V+90{mV})/20{mV});
      beta_h = 1.00{per_ms}
        /(1{dimensionless}+exp(-(V+42{mV})/10{mV}));
      ode(h, t) = alpha_h*(1{dimensionless}-h)-beta_h*h;
   enddef;
   def map between sodium_channel
     and sodium_channel_m_gate for
      vars V and V;
      vars t and t;
      vars m and m;
   enddef;
   def map between sodium_channel
     and sodium_channel_h_gate for
      vars V and V;
      vars t and t;
      vars h and h;
   enddef;
enddef;