In order to survive we need efficient ways to process information. The stress response system is one of the ways we process information. The stress response system is a result of evolution and enabled us to survive and thrive. Each stress response system is highly individual, the result of both genetics and shaped by early experience. When the body senses danger it creates chemical reactions that are designed to protect us from harm. Signals are sent from the brain to the adrenal glands to release stress hormones like adrenaline and cortisol. The heart starts to pound, the pupils dilate and the airways open. The body is primed to fight or run away.

What are the main parts of this system? The amygdala is the brain’s fear centre. The prefrontal cortex is involved in executive functioning like planning, judgement and regulating emotion and mood. The hypothalmic-pituatary-adrenal axis (HPA) begins the production of cortisol (long-acting stress hormones) by the adrenal glands. The sympatho-adrenomedullary axis (SAM) starts the production of adrenaline and noradrenaline (short-acting stress hormones) by the adrenal glands and the brain. The hippocampus processes emotional information and consolidates memory.

When we perceive threat the brain activates the SAM and HPA axis, triggering a fight-or-flight response. Messages from the SAM axis travel along nerves from the brain to the adrenal glands which then release adrenaline. This is what makes us feel scared. Adrenaline makes the heart beat faster, sending blood to the places where it is needed to help the body take action. The airways open so we can take in more oxygen. Blood pressure rises. Adrenaline and noradrenaline are stimulants which help you think clearly and find a way to safety.