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正反馈调节可以产生双稳性。正反馈回路(比如 X 激活 Y、Y 激活 X)将输出信号与输入信号耦合在一起，是细胞信号转导中的重要调节机制，它可以作为<font color="#ff8000">全或无All-or-none</font>信号开关<ref name="O. Brandman, J. E 2005">O. Brandman, J. E. Ferrell Jr., R. Li, T. Meyer, Science 310, 496 (2005)</ref>。许多生物系统（如非洲爪蟾卵“Xenopus”母细胞的成熟过程<ref>{{cite journal|author1=Ferrell JE Jr. |author2=Machleder EM |s2cid=34863795 |title=The biochemical basis of an all-or-none cell fate switch in Xenopus oocytes.|journal=Science|date=1998|volume=280|issue=5365|pages=895–8|pmid=9572732|doi=10.1126/science.280.5365.895|bibcode=1998Sci...280..895F }}<!--|accessdate=20 March 2015--></ref>、哺乳动物的钙信号转导过程和芽殖酵母“budding yeast”的极化）都包含时序正反馈回路，或者多时间尺度的反馈回路<ref name="O. Brandman, J. E 2005"/> 。具有多时间尺度反馈回路（或称为”双时间开关dual-time switches”）能够(a)增加调节: 两个开关具有独立可变的激活和失活时间，或(b)过滤噪声<ref name="O. Brandman, J. E 2005"/>。
Bistability can also arise in a biochemical system only for a particular range of parameter values, where the parameter can often be interpreted as the strength of the feedback. In several typical examples, the system has only one stable fixed point at low values of the parameter. A [[saddle-node bifurcation]] gives rise to a pair of new fixed points emerging, one stable and the other unstable, at a critical value of the parameter. The unstable solution can then form another saddle-node bifurcation with the initial stable solution at a higher value of the parameter, leaving only the higher fixed solution. Thus, at values of the parameter between the two critical values, the system has two stable solutions. An example of a dynamical system that demonstrates similar features is
Bistability can also arise in a biochemical system only for a particular range of parameter values, where the parameter can often be interpreted as the strength of the feedback. In several typical examples, the system has only one stable fixed point at low values of the parameter. A [[saddle-node bifurcation]] gives rise to a pair of new fixed points emerging, one stable and the other unstable, at a critical value of the parameter. The unstable solution can then form another saddle-node bifurcation with the initial stable solution at a higher value of the parameter, leaving only the higher fixed solution. Thus, at values of the parameter between the two critical values, the system has two stable solutions. An example of a dynamical system that demonstrates similar features is
在生物化学系统中，往往只有在特定的生化参数范围内才能产生双稳性，这些参数可以被解释为反馈强度。以单一参数 <math>r</math> 描述反馈强度的系统为例。当 <math>r</math> 比较小的时候，系统只有一个稳定不动点。当 <math>r</math> 增长到临界值 <math>r_0</math> 附近时，一个鞍结分岔引起一对新的不动点出现，一个是稳定的，一个是不稳定的。当 <math>r</math> 继续增长时，不稳定解与初始稳定解形成另一个鞍结分岔，只留下较高的固定解，在两个临界值之间的参数值，系统有两个稳定的解。
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