def model potassium_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 potassium_channel incl
         comp potassium_channel_n_gate;
      endcomp;
   enddef;
   def comp potassium_channel as
      var V: mV {pub: in, priv: out};
      var t: ms {pub: in, priv: out};
      var n: dimensionless {priv: in};
      var Ki: mM {pub: in};
      var Ko: mM {pub: in};
      var RTF: mV {init: 25};
      var E_K: mV;
      var g_K1: microS;
      var g_K2: microS;
      var i_K: nanoA {pub: out};
      E_K = RTF*ln(Ko/Ki);
      g_K1 = 1200{microS}*exp(-(V+90{mV})/50{mV})
        +15{microS}*exp((V+90{mV})/60{mV});
      g_K2 = 1200{microS}*pow(n, 4{dimensionless});
      i_K = (g_K1+g_K2)*(V-E_K);
   enddef;
   def comp potassium_channel_n_gate as
      var V: mV {pub: in};
      var t: ms {pub: in};
      var n: dimensionless {init: 0.01, pub: out};
      var alpha_n: per_ms;
      var beta_n: per_ms;
      alpha_n = -0.0001{per_mV_ms}*(V+50{mV})
        /(exp(-(V+50{mV})/10{mV})-1{dimensionless});
      beta_n = 0.0020{per_ms}*exp(-(V+90{mV})/80{mV});
      ode(n,t)= alpha_n*(1{dimensionless}-n)-beta_n*n;
   enddef;
   def map between environment
     and potassium_channel for
      vars V and V;
      vars t and t;
   enddef;
   def map between potassium_channel and
     potassium_channel_n_gate for
      vars V and V;
      vars t and t;
      vars n and n;
   enddef;
enddef;