The feedforward-feedback system of the hypothalamus-pituitary-adrenal axis

The hypothalamus-pituitary-adrenal axis is a complex system that is crucial for the survival of the organism stress. The mathematical model providing the qualitative behaviour of this endocrine system is needed. The mathematical model describing the feedforward-feedback mechanism of the hypothalamus-pituitary-adrenal axis is presented in this paper. The analysis via Hopf bifurcation reveals an important role of the composite delay time on the homeostasis and the pulsatility status of the hormone secretion in the body.