How the Adrenal Axis Works

What is the Adrenal Axis?

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.

What are the Adrenal Glands?

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.

Adrenal Cortex

The Adrenal Cortex is responsible for producing Cortisol and Aldosterone.

Cortisol

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

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.

Adrenal Medulla

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.

Cortisol Regulation

Glucocorticoid production is regulated by the Hypothalamic-Pituitary-Adrenal-Axis.

Physiology

• Corticotropin-releasing hormone (CRH) is secreted by the hypothalamus. The release of CRH is influenced by stress levels, time of day and serum cortisol levels.
• CRH travels in the blood and binds to specific receptors on the pituitary gland. This binding causes increased production of adrenocorticotropic hormone (ACTH).
• ACTH is released into the bloodstream and travels to the adrenal glands, where it binds to specific receptors on the adrenal cortex.
• The binding of ACTH to the receptors on the adrenal cortex stimulates the release of cortisol into the bloodstream, where it has a wide range of effects.
• Increased serum cortisol levels inhibit the production of CRH and ACTH via negative feedback, preventing the overproduction of cortisol.

Aldosterone Regulation

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:

• Sodium reabsorption
• Water reabsorption
• Potassium excretion

4. Aldosterone, therefore, causes a net increase in blood volume.

5. Increased blood volume inhibits the production of angiotensin II via negative feedback.

How to Become a Physiotherapy Student

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.

• Understand the entry requirements: Potential physiotherapy students need to understand any entry requirements a college or university may have and meet them. This may include minimum test scores, health requirements, and completion of undergraduate courses.
• Complete the program requirements: Physiotherapy students must complete the required coursework, practical placements and examinations. Check with your college or university to ensure you are meeting all of their requirements.
• Gather the necessary funding: Students need to be aware of tuition costs and other expenses in order to create a budget and seek financial aid if needed.
• Attend the prescribed clinical placements: Clinical placements are often an important part of physiotherapy programs. Students should attend placements to gain practical experience in the field.

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.