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fps
This script uses explicit Euler scheme. It makes it time steps per frame.
Full ring length is 1024×Δx.
u is the red curve, v is the blue one, Ta is
the green line, Ta_{av} level is shown by the black line.
Use Alt- r, s keys to control the script.

You can see here formation of a pacemaker in Aliev-Panfilov
model with non-oscillating kinetics. Pacemaking activity occurs because
the contraction of the medium (proportional to Ta(x) - Ta_{av })
that follows a propagating wave of excitation subsequently stretches the medium
in the neighborhood of the initiation site. This stretch induces a depolarizing
stretch activated current Is that initiates a subsequent excitation wave.

Excitation-contraction coupling model

We consider 1D lattice that consists of material points located
at x_{i} connected by springs. Similar to [1] all
springs follow Hooke's force-displacement relation and
may produce additional active contraction forces
f_{i}^{+} =
c(x_{i+1} - x_{i } - l_{o} )/l_{o} + Ta_{i } ≡
cδ_{i} + Ta_{i },
f_{i}^{-} =
-cδ_{i-1 } - Ta_{i-1 },

where l_{o }, c are the spring length and stiffness (we put c = 1),
Ta_{i} is the value of variable Ta dTa/dt = ε(u) (k_{T} u - Ta).
We consider the string with fixed length x_{n} - x_{o} = L.
As it is easy to check in that case
∑_{i=0}^{n-1} δ_{i} = 0.
Following [1] elastostatics is assumed in this model, i.e. the stationary
deformations corresponding to each given configuration of active
forces and boundary conditions are computed. In mechanical equilibrium
f_{i}^{+} + f_{i}^{+} = 0, ⇒
δ_{i} - δ_{i-1} =
-(Ta_{i} - Ta_{i-1 }),
δ_{i} = Ta_{av} - Ta_{i} ,
Ta_{av} = ∑_{i} Ta_{i }.
Physiological influence of contraction on cardiac tissue is given by a depolarising
stretch-activated current Is through stretch activated channels
Is = Gs ((1 + δ)^{1/2} - 1)(u - Es) ≅
0.5 Gs δ (u - Es) Gs = 1.5 and Es = 1 are the maximal conductance and reversal
potential of the stretch activated channels.
The stretch activated current is active only if δ > 0 (stretch).
(I have to set Gs = 0.5 to get 1D pacemaker).

[1] Louis D. Weise, Martyn P. Nash, Alexander V. Panfilov
"A Discrete Model to Study Reaction-Diffusion-Mechanics Systems" PLoS ONE, www.plosone.org, 1 July 2011, Volume 6, Issue 7, e21934