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The hypothalamic pituitary adrenal axis

The HPA axis

The hypothalamic pituitary adrenal (HPA) axis is our central stress response system. If a situation is judged as being stressful, the hypothalamus is activated and takes charge of the stress response.

HPA axis diagram explanation. The diagram begins with the Hypothalamus. There is an arrow extending from the Hypothalamus to the Anterior Pituitary. This arrow represents the Corticotropin Releasing hormone. There is then an arrow extending from the Anterior Pituitary to the Adrenal cortex. This arrow represents the Adrenocorticotropic Hormone. There is then an arrow which extends from the Adrenal cortex to the Anterior Pituitary and the Hypothalamus. This arrow represents Cortisol and the negative feedback of cortisol to both areas.
  • The stressor activates the Hypothalamic Pituitary Axis.
  • The hypothalamus stimulates the pituitary gland.
  • The pituitary gland secretes adrenocorticotropic hormone (ACTH).
  • ACTH stimulates the adrenal glands to produce the hormone corticosteroid.
  • Cortisol enables the body to maintain steady supplies of blood sugar.
  • Adequate and steady blood sugar levels help person to cope with prolonged stress, and helps the body to return to normal.
The Pituitary-Adrenal-Axis The Hypothalamus, Anterior Pituitary and Adrenal Cortex are all interconnected by arrows. The arrow extending from the Hypothalamus to the Anterior Pituitary resembles CRF (Corticotrophin Releasing Factor). The Anterior Pituitary has an arrow extending to the Adrenal Cortex. This arrow resembles ACTH Adrenocorticotrophic Hormone). Cortisol extends from the Adrenal Cortex Cortisol back to the Hypothalamus. Cortisol increases: blood glucose, blood pressure and amino acids. It also exerts a negative feedback effect on the Hypothalamus that inhibits further release of CRF.

Parts of the brain involved

Where there is a chronic or constant stress, threat or repeated trauma the system remains activated. This can lead to an alteration of the body’s response to stressors, immunity, inflammation, metabolism, hormone balance, energy, emotions, mood, sexuality and other important processes.

The diagram below shows the different parts of the brain that are involved in the HPA Axis.

Parts of the brain involved in the HPA axis diagram. Pointing out: the Hippocampus, Cerebellum, Hypothalamus, Brain stem, Amygdala, Pituitary Glad and Prefrontal Cortex.