The Physical Response to Stress

From the time a source of stress, or threat, is perceived a complex bio-psycho-chemical feedback look is triggered. In your research, you should explore the "Stress Response". What happens a threat is perceived? What part of the brain is stimulated, and what does it do? What are the "Stress Hormones", and what are their function? What are some of the immediate effects of stress? What are the long-term effects of stress?