Hi could someone explain the SAM pathway and HPA axis? As in what is the order of each because I've been seeing different variations. Thanks
In terms of stress, the SAM pathway (sympathetic-adrenomedullary system) and the HPA (hypothalamic-pituitary-adrenal) axis are biological functions that are both activated during different stages of the stress response. However, they are not massive parts of the study design, and besides potentially the extended response, I doubt that VCAA will assess you directly on these concepts.
The SAM pathway describes how the sympathetic nervous system initiates the fight-flight response in response to a stressor. When the body perceives a stressor, the hypothalamus signals to the
sympathetic nervous system to activate. The sympathetic nervous system then communicates to the
adrenal medulla, which is the inner part of the adrenal glands. The adrenal glands then secrete adrenaline and noradrenaline, which you might have learnt are the stress hormones which increase energy and arousal in the body. This thus is the activation of the fight-flight response.
The HPA axis is typically activated during the resistance stage of the GAS model after the stressor has been prolonged and the body cannot maintain the fight-flight response. This involves the release of cortisol as a stress hormone which increases the body's energy levels and equips it to continue to deal with the stress. After the body detects the prolonging of the stress, the
hypothalamus stimulates/activates the
pituitary gland, which is located in the brain nearby to the hypothalamus. The pituitary gland then secretes a hormone known as ACTH into the bloodstream. ACTH travels through the body and communicates to the
adrenal glands, which is then stimulated to secrete stress hormones called corticosteroids, the primary hormone released being cortisol. Once a certain level of cortisol has been reached in the body, it signals to the pituitary gland, which then signals to the hypothalamus to be switched off.
This is all really biological and isn't, again, a major part of the study design, so you don't need to know how to describe it in detail. However, it's interesting to know how it functions.
If you need clarification on any part of this, let me know.