I usually recommend that one start with the book The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma by Bessel van der Kolk. There are a plethora of resources out there on the subject and endless research articles on an array of different components of this area of study and practice. This Dr. van der Kolk is an excellent and accessible writer, and this book is a great place to start your reading. It is written in a manner easily accessible to all levels of understanding.
I have attached a single slide I use in presentations to describe the biological control of the stress response: The Hypothalmic - Pituitary - Adrenal Axis (HPA) and neuro-hormonal mechanism of response. The Hypothalmus is our 'smoke detector' which triggers a neuro - endocrine activation that release a plethora of stress mediators from cortisol, adrenalin, opiods etc. which act systemically to prepare the entire body for 'fight, flight, or freeze.' With chronic stress, these feedback systems are continually activated having widespread and deleterious effect on every biological system.