Applied Math Talk: Dynamics of neuroendocrine stress response given by Prof. Maria Rita D’Orsogna (CSUN)

The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system
that regulates numerous physiological processes. Disruptions are
correlated with stress-related diseases such as PTSD and major depression. We characterize “normal” and “diseased” states of the HPA axis as basins of attraction of a dynamical system describing the main hormones regulated by the HPA axis. Our model includes hormonal self-upregulation, release, synthesis; interaction,
delay and feedback mechanisms. External input is associated to psychological trauma, while parameter changes represent physiological damage. We show that transitions between the  “normal” and “diseased” states may be induced solely by
external input, with all physiological parameters unchanged, emphasizing
the severe consequences of psychological trauma. We also find that the
timing and duration of the traumatic event is an important determinant
of if and how stress disorders will manifest. Finally, we propose mechanisms whereby exposure therapy may act to normalize downstream dysregulation of the HPA axis.