When we first perceive a stressor, our sensory systems send signals to the limbic system, which is activated and the stressfulness of the situation is evaluated against a variety of factors such as past experience, and the current context.
These signals are integrated to initiate the appropriate hormonal, physiological and behavioural responses (Figure 4).
The hypothalamus releases the body's major stress hormone, corticotropin releasing factor (CRF), which then signals the pituitary to release adrenocorticotropic hormone (ACTH), which travels to the adrenals to initiate the secretion of the glucocorticoid hormones. The glucocorticoids then circulate to the brain where they can interact with their receptors. The hippocampus is an area rich in glucocorticoid receptors. Chronic activation of these receptors and high levels of circulating glucocorticoids can have harmful effects on the brain and body. It is thought that overactivation of the CRF system can lead to symptoms of anxiety and depression.