;;  -*- Hen -*-

;;
;; 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
	    
      ((input v)

       (const Vrest = -65)

       (component (type membrane-capacitance)
	   (const C = 1.0)
	   (output C))

       (component (type ionic-current) (name Na)

         (component (type gate)
		  
	    ;; rate functions
	    (defun amf (v)   (0.1  *  ((v + 40) / (1.0 - (exp ((neg (v + 40)) / 10))))))
	    (defun bmf (v)   (4.0  *  (exp ((neg (v + 65)) / 18))))
	    (defun ahf (v)   (0.07 *  (exp ((neg (v + 65)) / 20))))
	    (defun 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)))))

	    ;; state definitions exported by this component: Na_m Na_h 
	    )

	 (component (type pore)
		    (const  gbar_Na  = 120)
		    (output gbar_Na ) )

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

       (component (type ionic-current) (name K)

         (component (type gate)
		    
	    ;; rate functions
	    (defun anf (v)   (0.01  * ((v + 55) / (1 - (exp ((neg (v + 55)) / 10))))))
	    (defun 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)))))

	    ;; state definitions exported by this component: K_m K_h 

	    )

	 (component (type pore)
	    (const   gbar_K   = 36)
	    (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  = 0.3)
			     (output gbar_Leak ))
		  
	      (component (type permeating-ion) (name non-specific)
			 (const e_Leak = -54.4)
			 (output e_Leak ))
	      
	      ) ;; end leak current

      ))