Understanding depression and anxiety

2.1 The operation and control of the HPA axis

The following activity includes an interactive animation that will help you to appreciate the nature of stress and the role played by stress and the hypothalamic–pituitary–adrenal (HPA) axis when we come to consider the aetiology of emotional disorders such as depression and anxiety.

The animation is designed to help you understand the operation of the HPA axis – how it is controlled under normal conditions and how the controls are disrupted under conditions of chronic stress.

Activity 6  The operation and control of the hypothalamic–pituitary–adrenal (HPA) axis

Allow 1 hour

The stress response has evolved to mobilise the body and mind for action when a threat is perceived. The response has two main strands which act in parallel. The first is the sympathetic response, which triggers the release of adrenalin from the medulla of the adrenal gland. The second strand involves the hypothalamic–pituitary–adrenal, or HPA, axis, and triggers the release of cortisol from the cortex of the adrenal gland.

In this activity you will look at the operation and control of the HPA axis in three different conditions – first, under normal relaxed or baseline conditions; second, under normal conditions when there is an episode of stress which is resolved; and third, under conditions of continual or chronic stress when regulation of the HPA axis breaks down.

Overview of the HPA axis flow diagram

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Baseline, acute and chronic stages

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Re-run of HPA animation stages

Baseline

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Acute

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Chronic

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HPA axis components: more information

Identify two factors from the list below that would help to bring cortisol levels back to baseline levels after experiencing a stressful event.