Fig. 2.

A Stress-mediated Collapse of Regulatory Repertoire. Introducing an environmental stressor (orange node) into the HPA regulatory circuit (a) alters the stable attractor space in [CRH, ACTH, Cort, R, Stress] such that cycles supported at rest collapse (b). Under normal regulatory feedback tone and sensitivity, stress serves to galvanize the Healthy regulatory cycle while also allowing for transition to a pathologic stationary point (red asterisk). Alternatively, in the case of a heightened sensitivity to stress the previous stability landscape collapses altogether to 3 stationary points, one belonging to the medium to high range cortisol cycle (blue asterisk) and two belonging to the low to medium range cortisol regime (red asterisk)