Under ideal conditions the body maintains homeostatic balance. This is where the body has the ideal blood pressure, temperature, the right levels of glucose in the bloodstream, and so on. Then there comes stress which was a part of our evolutionary make-up as a survival mechanism. When faced with a tiger that just jumped out of the bushes the cortex uses the data it has collected to make a decision on an appropriate response to the startling stimulus. If the cortex perceives a real threat the brain automatically sends signals straight to the hypothalamus. The hypothalamus then releases a stress hormone known as CRF. Next, the hypothalamus also signals to the pituitary gland to release hormones (ACTH) along with epinephrine and cortisol into the blood-stream that energize all of the body’s organs preparing us for fight or flight. This all works from the autonomic nervous system that has two parts to keep the body in homeostasis, which are the sympathetic and parasympathetic nervous system.
Chronic stress, especially chronic psychological stress, can bring havoc upon the entire body. The heart starts working really hard, pumping with more force, pumping more frequently. Blood pressure is increasing, going through the blood vessels with more force. The blood vessels in response slowly begin to build up more muscle wrapping around them. This makes the blood vessels more rigid, which requires more force to get the blood through them. Now we are facing problems with hypertension. Enough of that slamming of blood against the walls of the blood vessels and you begin to get little bits of damage there, little bits of tearing and scarring that wind up getting inflamed. Then plaque starts sticking to these areas along with fat, glucose, and cholesterol. Once the coronary vessels are damaged, when you increase blood flow during a period of stress, they no longer vasodilate; they constrict.
Chronic or frequent stress with high cortisol levels are associated with a decrease in the body’s natural immune response, a decrease in DNA repair, and an increase in autoimmune diseases. This keeps the body out of homeostatic balance which set us up for all kinds of illnesses and diseases.
Chronic stress can lead to neuron death in the brain. Neuron loss in the hippocampus (referred to as hippocampal atrophy); neurons in the hippocampus have high concentration of receptors that bind cortisol, and long-term elevated cortisol levels induce chances that result in the death of these neurons.