Human Physiology: The Renin-Angiotensin-Aldosterone System Essay

The Renin-Angiotensin-Aldosterone system consists of a cascade of proteins and is involved in the processes of blood pressure regulation. The proteins included into the RAAS are Renin, Angiotensinogen, Angiotensin I and Angiotensin II (Levick 200).

If a person’s blood pressure is normal and the salt in the organism is in homeostasis, the Renin-Angiotensin-Aldosterone system (RAAS) is not activated. In the case when blood pressure decreases, RAAS becomes activated in the following way. Firstly, low blood pressure and associated sodium concentration changes cause liver to release Angiotensinogen (Levick 201). Secondly, kidneys secrete an enzyme named Renin that cleaves Angiotensinogen (Levick 201). As a result, Angiotensin I is formed, although still inactive.

Furthermore, Angiotensin I is converted by ACE (angiotensin converting enzyme). ACE is largely present in the pulmonary circulation system, but it is also produced by the vascular endothelium of certain tissues (e.g. brain, adrenal gland, heart and kidney) (Levick 204). ACE causes inactive Angiotensin I to convert into vasoactive Angiotensin II (Levick 204). The action of Angiotensin II is the following: it binds the AT1 receptors located on vascular endothelium and reduces the synthesis of nitric oxide (Levick 207). Low level of nitric oxide and AT1 receptor stimulation lead to vasoconstriction (Levick 207).

In addition, AT1 receptor stimulation caused by Angiotensin II makes the adrenal cortex to produce Aldosterone (Sherwood 351). The presence of Aldosterone leads to retention of sodium (Sherwood 351).

Vasoconstriction and sodium retention lead to the increase of blood pressure. As the blood pressure increases, kidneys stop producing Renin. It should be noted that Angiotensin II also causes the release of ADH (antidiuretic hormone), also referred to as vasopressin, in hypothalamus (Sherwood 353). Vasopressin also causes vasoconstriction, stimulates the absorption of water by kidneys and influences the functioning of the central nervous system, causing the need for salt and thirst (Sherwood 354). Hence, the activation of RAAS would lead to the stabilization of blood pressure and would also cause thirst.

 

Works Cited

Levick, J. Rodney. An Introduction to Cardiovascular Physiology. Butterworth-Heinemann, 2013.

Sherwood, Lauralee. Human Physiology: From Cells to Systems. Cengage Learning, 2015.

The terms offer and acceptance. (2016, May 17). Retrieved from

[Accessed: March 28, 2024]

"The terms offer and acceptance." freeessays.club, 17 May 2016.

[Accessed: March 28, 2024]

freeessays.club (2016) The terms offer and acceptance [Online].
Available at:

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"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: March 28, 2024]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: March 28, 2024]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: March 28, 2024]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: March 28, 2024]
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