;;
;; This model is used to calculate the channel conductance assuming
;; some initial state. The calculation is based on sodium ion flow,
;; potassium ion flow and leakage ion flow. (Hodgkin, A. L. and Huxley,
;; A. F. (1952) "A Quantitative Description of Membrane Current and its
;; Application to Conduction and Excitation in Nerve" Journal of
;; Physiology 117: 500-544)
;;

nemo-model
 
 hodgkin-huxley-syn
    
      input v
 
      const Vrest = -65
 
      component (type membrane-capacitance)
		 const C = 1.0
		 output C

      component (type defaults) 
         const V_t = -35
         const t_ref = 2.0
         output V_t t_ref

      component (type post-synaptic-conductance) (name Syn)
        
        input (w from event)
        
        const tauA = 30.0
        const tauB = 500.0
        const e = 0
        
        const tau1 = (if ((tauA / tauB) > .9999) then (0.9999 * tauB) else tauA)
        const tau2 = tauB

        const tp = ((tau1 * tau2) / (tau2 - tau1) * ln (tau2 / tau1))
        const scale_factor = (1 / (neg (exp (neg (tp) / tau1)) + exp (neg (tp) / tau2)))
        
        transient (A) = (neg (A) / tau1) (onevent (A + (w * scale_factor))) (initial 0)
        transient (B) = (neg (B) / tau2) (onevent (B + (w * scale_factor))) (initial 0)
                
        g =  (B - A)
        
        output g e scale_factor

      component (type ionic-current) (name Na)

         component (type gate)
	    ;; rate functions
	    fun amf (v)   (0.1  *  ((v + 40) / (1.0 - (exp ((neg (v + 40)) / 10)))))
	    fun bmf (v)   (4.0  *  (exp ((neg (v + 65)) / 18)))
	    fun ahf (v)   (0.07 *  (exp ((neg (v + 65)) / 20)))
	    fun bhf (v)   (1.0  /  (1.0 + (exp ((neg (v + 35)) / 10))))
	    hh-ionic-gate 
	     Na  ;; ion name: exported variables will be of the form {ion}_{id}
	      initial-m (amf (Vrest) / (amf (Vrest) + bmf (Vrest))) 
	      initial-h (ahf (Vrest) / (ahf (Vrest) + bhf (Vrest))) 
	      m-power   3
	      h-power   1
	      m-alpha   (amf (v))
	      h-alpha   (ahf (v))
	      m-beta    (bmf (v))
	      h-beta    (bhf (v))

         component (type permeating-ion) (name na)
		    const e_Na = 50
		    output e_Na

         component (type pore)
		    const  gbar_Na  = 0.12
		    output gbar_Na

      component (type ionic-current) (name K)

         component (type gate)
		    
	    ;; rate functions
	    fun anf (v)   (0.01  * ((v + 55) / (1 - (exp ((neg (v + 55)) / 10)))))
	    fun bnf (v)   (0.125 * (exp ((neg (v + 65)) / 80)))
	    
	    hh-ionic-gate 
	     K  ;; ion name
	      initial-m (anf (Vrest) / (anf (Vrest) + bnf (Vrest)))
	      m-power 4
	      h-power 0 ;; h-power is 0, therefore h further declarations are omitted
	      m-alpha (anf (v))
	      m-beta  (bnf (v))


         component (type pore)
	    const   gbar_K   = 0.036
	    output  gbar_K

         component (type permeating-ion) (name k)
		    const e_K = -77
		    output e_K

      component (type ionic-current) (name Leak)
		  
                component (type pore)
			  const  gbar_Leak  = 0.0003
			  output gbar_Leak
		  
	        component (type permeating-ion) (name non-specific)
			 const e_Leak = -54.4
			 output e_Leak