我們提出一個從詳細的生理學離子模型簡化後導出的二變數模型，並驗證該二變數動力學系統可以捕抓到與完整離子模型相似的動力學分叉圖。
將零斜率線分析和疊代圖分析應用在我們提出的二變數模型藉此研究心臟細胞的動力響應和分叉行為。
理論結果表明，細胞膜內鈣離子在肌質和肌漿網之間的循環在心臟動力學的穩定性中起著至關重要的作用。
此外，歸功於二變數模型的簡潔，我們可以更容易看到藏在雙週期心臟動力學背後的機制。

We propose a two-variable reduced model that is derived from a detailed physiological ionic model and show that this two-variable dynamical system captures realistically the essence of the bifurcation behavior as seen in the ionic model. The dynamical response and bifurcation behavior of a cardiac cell are investigated with the proposed two-variable model by nullcline analysis and iterative map analysis. The theoretical results indicate that intracellular calcium cycling between bulk myoplasm and sarcoplasmic reticulum (SR) plays a crucial role in influencing the stability of cardiac dynamics.
In addition, due to the simplicity of the two-variable model, one can see easily the mechanism behind the period-2 cycle of calcium dynamics.

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