Figure 6.
![Figure 6. Threshold behavior of the toy couplon at constant SR calcium. (A) Dynamics of the “toy model” of the couplon, when the variable casr ([Ca2+]JSR) is held at a fixed value. There is a sharp threshold value of nopen above which CICR will regenerate until almost all RyRs are open, and below which it will fall exponentially to near zero. (B) The CICR threshold is a steep function of JSR calcium, allowing CICR to cease regeneration when the JSR is depleted.](https://cdn.rupress.org/rup/content_public/journal/jgp/142/3/10.1085_jgp.201311034/5/jgp_201311034_fig6.jpeg?Expires=1773461611&Signature=ink~cObXwVCLwfp-H2lp49Dj7ioe9d3yQ3FBj-q3ucum1pocmL2FyCErGmKBYMaNNRkB99cQ~SkiGod9YmDilPTRKgedsVVjkCc1KTgz7OVe8Gz8DusRbThD2qheygFgurCFBGJ3NhbTEjpPH3mZiYmqt6RxBuPe54H11lUhpHimeKk89WnHCgTlEqLnpPw6t~NLoqJLoGLjdG8MYHjAtcmeouJmXEdRWKlmrtL11wJXs09qo39xv7UWYHT6GwGeeLI-AXel7BwanFSvngrskxVI8hWQy9OqkHxEGT8--7nEPtF7xj622gDtdN5ang9vF2OCEj3Fnddt-NiBVranmg__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Threshold behavior of the toy couplon at constant SR calcium. (A) Dynamics of the “toy model” of the couplon, when the variable casr ([Ca2+]JSR) is held at a fixed value. There is a sharp threshold value of nopen above which CICR will regenerate until almost all RyRs are open, and below which it will fall exponentially to near zero. (B) The CICR threshold is a steep function of JSR calcium, allowing CICR to cease regeneration when the JSR is depleted.
