The Adrenal Axis (also known as the Hypothalamic-Pituitary-Adrenal Axis) refers to a complex series of interactions and feedback loops between the Hypothalamus, Pituitary and Adrenal Glands. This system is responsible for regulating the body's response to stress, immune function, energy expenditure, mood, emotion and libido.
The Adrenal Glands are located just above each kidney and produce a number of hormones, including Cortisol, Aldosterone, Adrenaline and Noradrenaline. Each gland is composed of an outer cortex and an inner medulla.
The Adrenal Cortex is responsible for producing Cortisol and Aldosterone.
Cortisol is a steroid hormone (Glucocorticoid) that is released in response to stress and low blood glucose levels. Its functions include: increasing blood glucose levels by promoting gluconeogenesis; suppressing the immune system; and aiding the metabolism of fat, protein and carbohydrates.
Aldosterone is also a steroid hormone (Mineralocorticoid) whose main function is to increase blood volume. This is achieved by promoting the reabsorption of sodium and water, whilst increasing the excretion of potassium.
The Adrenal Medulla produces Adrenaline and Noradrenaline (both having similar physiological effects). Adrenaline and Noradrenaline are released during periods of stress as part of the "fight or flight" response, resulting in increased heart rate, blood pressure and muscle perfusion. The release of Adrenaline and Noradrenaline is under the direct control of the hypothalamus.
Glucocorticoid production is regulated by the Hypothalamic-Pituitary-Adrenal-Axis.
1. Low blood volume stimulates the release of angiotensin II.
2. Angiotensin II stimulates the adrenal cortex to produce aldosterone.
3. Aldosterone has a number of different effects, including:
4. Aldosterone, therefore, causes a net increase in blood volume.
5. Increased blood volume inhibits the production of angiotensin II via negative feedback.
Becoming a physiotherapy student requires a commitment to education. Before you can become a practicing physiotherapist, you must complete an accredited program in a college or university. This article outlines the steps necessary to become a successful physiotherapy student.
Completion of a physiotherapy program can open the door to a rewarding career. Completing these steps will get you started on the path to becoming a successful physiotherapy student.
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