Model Mathematics

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Component: environment

Component: membrane

FVRT = \frac{F V}{R T} FVRT_Ca = 2 FVRT i_Stim = \{\begin{matrix} stim_amplitude if time - (⌊ \frac{time}{stim_period} ⌋ stim_period) \geq 0 \land time - (⌊ \frac{time}{stim_period} ⌋ stim_period) ≦ stim_duration \\ 0 otherwise \end{matrix} \frac{d}{d time} (V) = \frac{- (i_Na + i_t + i_ss + i_f + i_K1 + i_B_Na + i_B_K + i_NaK + i_CaB2 + i_Ncx2 + i_pCa2 + i_LCC2 + i_Stim)}{Cm}

Component: cell_geometry

Component: sodium_current

E_Na = \frac{R T}{F} \ln (\frac{Na_o}{Na_i}) i_Na = g_Na m^{3} h j (V - E_Na)

Component: sodium_current_m_gate

m_infinity = \frac{1}{1 + ⅇ^{\frac{V + 45}{- 6.5}}} tau_m = \frac{1.36}{\frac{0.32 (V + 47.13)}{1 - (ⅇ^{(- 0.1) (V + 47.13)})} + 0.08 ⅇ^{\frac{- V}{11}}} \frac{d}{d time} (m) = \frac{m_infinity - m}{tau_m}

Component: sodium_current_h_gate

h_infinity = \frac{1}{1 + ⅇ^{\frac{V + 76.1}{6.07}}} tau_h = \{\begin{matrix} 0.4537 (1 + ⅇ^{\frac{- (V + 10.66)}{11.1}}) if V \geq - 40 \\ \frac{3.49}{0.135 ⅇ^{\frac{- (V + 80)}{6.8}} + 3.56 ⅇ^{0.079 V} + 310000 ⅇ^{0.35 V}} otherwise \end{matrix} \frac{d}{d time} (h) = \frac{h_infinity - h}{tau_h}

Component: sodium_current_j_gate

j_infinity = \frac{1}{1 + ⅇ^{\frac{V + 76.1}{6.07}}} tau_j = \{\begin{matrix} \frac{11.63 (1 + ⅇ^{(- 0.1) (V + 32)})}{ⅇ^{(- 0.0000002535) V}} if V \geq - 40 \\ \frac{3.49}{\frac{V + 37.78}{1 + ⅇ^{0.311 (V + 79.23)}} ((- 127140) ⅇ^{0.2444 V} - (0.00003474 ⅇ^{(- 0.04391) V})) + \frac{0.1212 ⅇ^{(- 0.01052) V}}{1 + ⅇ^{(- 0.1378) (V + 40.14)}}} otherwise \end{matrix} \frac{d}{d time} (j) = \frac{j_infinity - j}{tau_j}

Component: Ca_independent_transient_outward_K_current

E_K = \frac{R T}{F} \ln (\frac{K_o}{K_i}) i_t = g_t r (a s + b s_slow) (V - E_K)

Component: Ca_independent_transient_outward_K_current_r_gate

r_infinity = \frac{1}{1 + ⅇ^{\frac{V + 10.6}{- 11.42}}} tau_r = \frac{100}{45.16 ⅇ^{0.03577 (V + 50)} + 98.9 ⅇ^{(- 0.1) (V + 38)}} \frac{d}{d time} (r) = \frac{r_infinity - r}{tau_r}

Component: Ca_independent_transient_outward_K_current_s_gate

s_infinity = \frac{1}{1 + ⅇ^{\frac{V + 45.3}{6.8841}}} tau_s = 20 ⅇ^{- ({(\frac{V + 70}{25})}^{2})} + 35 \frac{d}{d time} (s) = \frac{s_infinity - s}{tau_s}

Component: Ca_independent_transient_outward_K_current_s_slow_gate

s_slow_infinity = \frac{1}{1 + ⅇ^{\frac{V + 45.3}{6.8841}}} tau_s_slow = 1300 ⅇ^{- ({(\frac{V + 70}{30})}^{2})} + 35 \frac{d}{d time} (s_slow) = \frac{s_slow_infinity - s_slow}{tau_s_slow}

Component: steady_state_outward_K_current

i_ss = g_ss r_ss s_ss (V - E_K)

Component: steady_state_outward_K_current_r_ss_gate

r_ss_infinity = \frac{1}{1 + ⅇ^{\frac{V + 11.5}{- 11.82}}} tau_r_ss = \frac{10000}{45.16 ⅇ^{0.03577 (V + 50)} + 98.9 ⅇ^{(- 0.1) (V + 38)}} \frac{d}{d time} (r_ss) = \frac{r_ss_infinity - r_ss}{tau_r_ss}

Component: steady_state_outward_K_current_s_ss_gate

s_ss_infinity = \frac{1}{1 + ⅇ^{\frac{V + 87.5}{10.3}}} tau_s_ss = 2100 \frac{d}{d time} (s_ss) = \frac{s_ss_infinity - s_ss}{tau_s_ss}

Component: inward_rectifier

i_K1 = \frac{(\frac{0.048}{ⅇ^{\frac{V + 37}{25}} + ⅇ^{\frac{V + 37}{- 25}}} + 0.01) 0.001}{1 + ⅇ^{\frac{V - (E_K + 76.77)}{- 17}}} + \frac{g_K1 (V - (E_K + 1.73))}{(1 + ⅇ^{\frac{1.613 F (V - (E_K + 1.73))}{R T}}) (1 + ⅇ^{\frac{K_o - 0.9988}{- 0.124}})}

Component: hyperpolarisation_activated_current

f_K = 1 - f_Na i_f_Na = g_f y f_Na (V - E_Na) i_f_K = g_f y f_K (V - E_K) i_f = i_f_Na + i_f_K

Component: hyperpolarisation_activated_current_y_gate

y_infinity = \frac{1}{1 + ⅇ^{\frac{V + 138.6}{10.48}}} tau_y = \frac{1000}{0.11885 ⅇ^{\frac{V + 80}{28.37}} + 0.5623 ⅇ^{\frac{V + 80}{- 14.19}}} \frac{d}{d time} (y) = \frac{y_infinity - y}{tau_y}

Component: background_currents

i_B_Na = g_B_Na (V - E_Na) i_B_K = g_B_K (V - E_K) i_B = i_B_Na + i_B_K

Component: sodium_potassium_pump

nu_1 = gamma1 {(1 + \frac{KdNaio}{Na_i})}^{2} (1 + \frac{KdNais}{Na_i} ⅇ^{\frac{\frac{(- Delta) F V}{R}}{T}}) + {(1 + \frac{alpha}{K_o})}^{2} (1 + \frac{Na_o}{KdNaes} ⅇ^{\frac{\frac{(- (1 - Delta)) F V}{R}}{T}}) i_NaK = \frac{i_NaK_max (gamma1 + 1)}{nu_1}

Component: extracellular_ion_concentrations

Component: CaRU

Component: CaRU_Transitions

expVL = ⅇ^{\frac{V - V_L}{del_VL}} alpha_p = \frac{expVL}{t_L (expVL + 1)} alpha_m = \frac{phi_L}{t_L} beta_poc = \frac{{C_oc}^{2}}{t_R ({C_oc}^{2} + {K_RyR}^{2})} beta_pcc = \frac{{Ca_i}^{2}}{t_R ({Ca_i}^{2} + {K_RyR}^{2})} beta_m = \frac{phi_R}{t_R} epsilon_pco = \frac{C_co (expVL + a1)}{tau_L K_L (expVL + 1)} epsilon_pcc = \frac{Ca_i (expVL + a1)}{tau_L K_L (expVL + 1)} epsilon_m = \frac{b1 (expVL + a1)}{tau_L (b1 expVL + a1)} mu_poc = \frac{{C_oc}^{2} + c {K_RyR}^{2}}{tau_R ({C_oc}^{2} + {K_RyR}^{2})} mu_pcc = \frac{{Ca_i}^{2} + c {K_RyR}^{2}}{tau_R ({Ca_i}^{2} + {K_RyR}^{2})} mu_moc = \frac{theta_R d ({C_oc}^{2} + c {K_RyR}^{2})}{tau_R (d {C_oc}^{2} + c {K_RyR}^{2})} mu_mcc = \frac{theta_R d ({Ca_i}^{2} + c {K_RyR}^{2})}{tau_R (d {Ca_i}^{2} + c {K_RyR}^{2})}

Component: DS_Calcium_Concentrations

C_cc = Ca_i C_co = \frac{Ca_i + \frac{J_R}{g_D} Ca_SR}{1 + \frac{J_R}{g_D}} C_oc = \{\begin{matrix} \frac{Ca_i + \frac{\frac{J_L}{g_D} Ca_o FVRT_Ca ⅇ^{- FVRT_Ca}}{1 - (ⅇ^{- FVRT_Ca})}}{1 + \frac{\frac{J_L}{g_D} FVRT_Ca}{1 - (ⅇ^{- FVRT_Ca})}} if | FVRT_Ca | > 0.000000001 \\ \frac{Ca_i + \frac{J_L}{g_D} Ca_o}{1 + \frac{J_L}{g_D}} otherwise \end{matrix}

Component: LCC_and_RyR_fluxes

J_Rco = \frac{J_R (Ca_SR - Ca_i)}{1 + \frac{J_R}{g_D}} J_Roo = \{\begin{matrix} \frac{J_R ((Ca_SR - Ca_i) + \frac{\frac{J_L}{g_D} FVRT_Ca}{1 - (ⅇ^{- FVRT_Ca})} (Ca_SR - (Ca_o ⅇ^{- FVRT_Ca})))}{1 + \frac{J_R}{g_D} + \frac{\frac{J_L}{g_D} FVRT_Ca}{1 - (ⅇ^{- FVRT_Ca})}} if | FVRT_Ca | > 0.00001 \\ \frac{J_R ((Ca_SR - Ca_i) + \frac{\frac{J_L}{g_D} 0.00001}{1 - (ⅇ^{- 0.00001})} (Ca_SR - (Ca_o ⅇ^{- 0.00001})))}{1 + \frac{J_R}{g_D} + \frac{\frac{J_L}{g_D} 0.00001}{1 - (ⅇ^{- 0.00001})}} otherwise \end{matrix} J_Loc = \{\begin{matrix} \frac{\frac{J_L FVRT_Ca}{1 - (ⅇ^{- FVRT_Ca})} (Ca_o ⅇ^{- FVRT_Ca} - Ca_i)}{1 + \frac{\frac{J_L}{g_D} FVRT_Ca}{1 - (ⅇ^{- FVRT_Ca})}} if | FVRT_Ca | > 0.00001 \\ \frac{\frac{J_L 0.00001}{1 - (ⅇ^{- 0.00001})} (Ca_o ⅇ^{- 0.00001} - Ca_i)}{1 + \frac{\frac{J_L}{g_D} 0.00001}{1 - (ⅇ^{- 0.00001})}} otherwise \end{matrix} J_Loo = \{\begin{matrix} \frac{\frac{J_L FVRT_Ca}{1 - (ⅇ^{- FVRT_Ca})} ((Ca_o ⅇ^{- FVRT_Ca} - Ca_i) + \frac{J_R}{g_D} (Ca_o ⅇ^{- FVRT_Ca} - Ca_SR))}{1 + \frac{J_R}{g_D} + \frac{\frac{J_L}{g_D} FVRT_Ca}{1 - (ⅇ^{FVRT_Ca})}} if | FVRT_Ca | > 0.00001 \\ \frac{\frac{J_L 0.00001}{1 - (ⅇ^{- 0.00001})} ((Ca_o ⅇ^{- 0.00001} - Ca_i) + \frac{J_R}{g_D} (Ca_o ⅇ^{- 0.00001} - Ca_SR))}{1 + \frac{J_R}{g_D} + \frac{\frac{J_L}{g_D} 0.00001}{1 - (ⅇ^{- 0.00001})}} otherwise \end{matrix}

Component: CaRU_states

denom = (alpha_p + alpha_m) ((alpha_m + beta_m + beta_poc) (beta_m + beta_pcc) + alpha_p (beta_m + beta_poc)) P1 = \frac{alpha_p beta_m (alpha_p + alpha_m + beta_m + beta_pcc)}{denom} P2 = \frac{alpha_m (beta_pcc (alpha_m + beta_m + beta_poc) + beta_poc alpha_p)}{denom} P3 = \frac{alpha_p (beta_poc (alpha_p + beta_m + beta_pcc) + beta_pcc alpha_m)}{denom} P4 = \frac{alpha_m beta_m (alpha_m + alpha_p + beta_m + beta_poc)}{denom}

Component: CaRU_reduced_states

r_1 = P1 mu_poc + P4 mu_pcc r_2 = \frac{alpha_p mu_moc + alpha_m mu_mcc}{alpha_p + alpha_m} r_3 = \frac{beta_m mu_pcc}{beta_m + beta_pcc} r_4 = mu_mcc r_5 = P2 epsilon_pco + P4 epsilon_pcc r_6 = epsilon_m r_7 = \frac{alpha_m epsilon_pcc}{alpha_p + alpha_m} r_8 = epsilon_m z_4 = 1 - z_1 - z_2 - z_3 \frac{d}{d time} (z_1) = (- (r_1 + r_5)) z_1 + r_2 z_2 + r_6 z_3 \frac{d}{d time} (z_2) = (r_1 z_1 - ((r_2 + r_7) z_2)) + r_8 z_4 \frac{d}{d time} (z_3) = (r_5 z_1 - ((r_6 + r_3) z_3)) + r_4 z_4

Component: RyR_current

J_R1 = P3 J_Roo + J_Rco P2 J_R3 = \frac{J_Rco beta_pcc}{beta_m + beta_pcc} i_RyR1 = \frac{(z_1 J_R1 + z_3 J_R3) N}{Vmyo} i_RyR2 = i_RyR1

Component: LCC_current

J_L1 = J_Loo P3 + J_Loc P1 J_L2 = \frac{J_Loc alpha_p}{alpha_p + alpha_m} i_LCC1 = \frac{(z_1 J_L1 + z_2 J_L2) N}{Vmyo} i_LCC2 = (- i_LCC1) 2 F Vmyo_uL

Component: Na_Ca_Exchanger

i_Ncx1 = \frac{g_NCX (ⅇ^{eta FVRT} {Na_i}^{3} Ca_o - (ⅇ^{(eta - 1) FVRT} {Na_o}^{3} Ca_i))}{({Na_o}^{3} + {K_mNa}^{3}) (Ca_o + K_mCa) (1 + k_sat ⅇ^{(eta - 1) FVRT})} i_Ncx2 = i_Ncx1 F Vmyo_uL

Component: SERCA

i_SERCA = \frac{g_SERCA {Ca_i}^{2}}{{K_SERCA}^{2} + {Ca_i}^{2}}

Component: SarcolemMal_Ca_pump

i_pCa1 = \frac{g_pCa Ca_i}{K_mpCa + Ca_i} i_pCa2 = i_pCa1 2 F Vmyo_uL

Component: Background_Ca_current

E_Ca = \frac{R T}{2 F} \ln (\frac{Ca_o}{Ca_i}) i_CaB1 = g_CaB (E_Ca - V) i_CaB2 = (- i_CaB1) 2 F Vmyo_uL

Component: SR_Ca_leak_current

i_SR = g_SRl (Ca_SR - Ca_i)

Component: troponin_Ca_buffer

i_TRPN = k_m_TRPN (B_TRPN - TRPN) - (k_p_TRPN TRPN Ca_i)

Component: calmodulin_Ca_buffer

beta_CMDN = {(1 + \frac{k_CMDN B_CMDN}{{(k_CMDN + Ca_i)}^{2}} + \frac{EGTA_tot KmEGTA}{{(KmEGTA + Ca_i)}^{2}})}^{- 1}

Component: intracellular_ion_concentrations

\frac{d}{d time} (Na_i) = \frac{(- (i_Na + i_B_Na + i_Ncx2 3 + i_NaK 3 + i_f_Na)) 1}{Vmyo_uL F} \frac{d}{d time} (K_i) = \frac{(- (i_Stim + i_ss + i_B_K + i_t + i_K1 + i_f_K + (- 2) i_NaK)) 1}{Vmyo_uL F} \frac{d}{d time} (TRPN) = i_TRPN \frac{d}{d time} (Ca_i) = beta_CMDN ((i_RyR2 - i_SERCA) + i_SR + i_TRPN - (\frac{(- 2) i_Ncx2 + i_LCC2 + i_pCa2 + i_CaB2}{2 Vmyo_uL F})) \frac{d}{d time} (Ca_SR) = \frac{Vmyo_uL}{VSR_uL} ((- i_RyR2) + i_SERCA - i_SR)