Content Writer
The renin–angiotensin system (RAS) is a hormone system that helps regulate the blood pressure and fluid balance in the human body.
- The majority of the system is made up of three hormones, namely renin, angiotensin II, and aldosterone.
- They are governed by the rate of renal blood flow in the primary stage.
- It is also known as renin–angiotensin–aldosterone system (RAAS).
- The renin–angiotensin system consists of hormones, proteins and enzymes.
- It is activated when there is a drop in blood pressure and blood volume on a long-term basis.
- The system is also activated when the concentration of sodium chloride decreases.
- It coordinates systemic vascular resistance on a long-term basis.
Key Terms: Renin-Angiotensin System, Hormones, Blood Pressure, Blood Volume, Enzymes, Proteins, Aldosterone, Angiotensin, Cells, Kidney, Lungs, Amino Acids, Tissues, Human Body
What is the Renin-Angiotensin System?
[Click Here for Sample Questions]
The renin-angiotensin system is a hormonal system that regulates arterial blood pressure and sodium concentration in the circulation.
- When renin is released into the bloodstream, it interacts with angiotensinogen (a circulating layer).
- It will produce decapeptide angiotensin I through proteolytic cleavage.
- Angiotensin transforming enzyme is present in the vascular endothelium.
- It helps in separating the two amino acids in order to produce angiotensin II (AII).
- Angiotensin II (AII) is also produced by other tissues in the body, such as the brain and heart.
The renin-angiotensin system is made up of the following members:
- Renin
- Angiotensin I
- Angiotensin II
- Angiotensin-Converting Enzyme (ACE)
Read More:
| Chapter Related Concepts | ||
|---|---|---|
| Control and coordination | Deltoid Muscles | Bones of the Ankle |
| Central nervous system | Types of Joints | Pelvic Bones |
Factors of Renin-Angiotensin System
[Click Here for Sample Questions]
The first stage of RAAS includes the secretion of the enzyme renin. Renin is released by the renal juxtaglomerular apparatus (JGA) granular cells in response to one of three factors:
- Macula densa cells detect reduced salt transport to the distal convoluted tubule.
- Afferent arteriole baroreceptors observe reduced perfusion pressure in the kidney.
- The JGA is stimulated sympathetically via one adrenoreceptor.
Atrial natriuretic peptide (ANP), which is released by stretched atria in response to rises in blood pressure, inhibits the release of renin.
Renin-Angiotensin System
Function of Renin-Angiotensin System
[Click Here for Sample Questions]
The major functions of the Renin-angiotensin system are listed below. -
- The construction of the resistance vessels helps in increased arterial pressure.
- It will also increase systemic vascular resistance.
- Renin-angiotensin system increases the body's water retention by stimulating salt delivery at renal tubular sites.
- It increases liquid retention by the kidneys.
- This is done by stimulating the release of vasopressin from the posterior pituitary.
- The renin-angiotensin system optimizes sympathetic adrenergic activity by releasing norepinephrine from sympathetic nerves.
- It prevents norepinephrine absorption.
- Another important function is that it stimulates both vascular and cardiac hypertrophy.
- The renin-angiotensin system is regulated by processes that favour the release of renin.
- It is regulated by natriuretic peptides generated by the human heart, which act as a major counter-regulatory system.
Importance of Renin-Angiotensin System
[Click Here for Sample Questions]
The importance of the renin-angiotensin system is as follows:
- The renin-angiotensin system regulates and maintains blood pressure in the cells.
- When a person's blood pressure drops or rises, this system responds by releasing renin into the bloodstream.
- In the treatment of heart failure and hypertension, manipulative treatments play a crucial role.
- ACE inhibitors and receptor blockers are used to reduce arterial blood pressure and blood volume.
Dual blockade employs a combination of angiotensin II receptor blockers and angiotensin-converting enzyme I inhibitors or therapeutic methods such as direct renin inhibition with aliskiren, a recently approved hypertension therapy.
- It also reduces ventricular afterload and ventricular preload, as well as vascular hypertrophy and reverse cardiac failure.
- Patients with renal and other cardiac disorders benefit more from therapeutic techniques.
- It aims for total suppression of the Renin-angiotensin system.
Angiotensinogen and Angiotensin I
[Click Here for Sample Questions]
Angiotensinogen is a liver-produced precursor protein for the hormone angiotensin I. Renin catalyses a reaction that transforms the angiotensinogen protein into angiotensin I.
- It is a precursor hormone that is converted to an active hormone called angiotensin II in the lungs.
- The conversion is done with an enzyme called angiotensin-converting enzyme.
- The function of angiotensinogen is to act as a precursor to angiotensin I.
- Renin cleaves or breaks apart angiotensinogen.
- It becomes smaller as it is dismantled, and its name also becomes shorter.
- As a result, it's currently known simply as angiotensin I.
- Angiotensin I decides to have a child and give it the name Angiotensin I.
- As a result, when angiotensin I is transformed in the lungs by an enzyme called ACE, it produces angiotensin II, or angiotensin junior.
Angiotensin I
Angiotensin-Converting Enzyme (ACE) and Angiotensin II
[Click Here for Sample Questions]
The angiotensin-converting enzyme, or ACE for short, is an enzyme that converts angiotensin I into angiotensin II and is found primarily in the lungs. When angiotensin II is produced, it has a significant impact on the body.
- Angiotensin II is a vasoconstrictor hormone that raises renal perfusion pressure, and glomerular filtration rate.
- It also constricts blood vessels throughout the body to raise systemic blood pressure.
The angiotensin-converting enzyme also works in the kidneys to keep blood pressure in the glomerulus normal, allowing the glomerular filtration rate to remain normal even when blood pressure is low.
Angiotensin-Converting Enzyme (ACE) and Angiotensin II
Read More:
| Class 11 Biology Related Concepts | ||
|---|---|---|
| Human Body - Anatomy & Physiology | Ball and Socket Joint | Types of Movement |
| Locomotion and Movement | Paralysis Symptoms | Muscular Tissue |
Things to Remember
- The renin-angiotensin system is a hormonal system that regulates arterial blood pressure and sodium concentration.
- Potassium is secreted into the tubules, which become part of urine and are expelled in exchange for sodium.
- Antidiuretic hormone (ADH), also known as vasopressin, is released in response to angiotensin II.
- ADH is produced in the hypothalamus and released from the posterior pituitary gland.
- The RAAS is responsible for a long-term increase in blood volume and arterial tone.
- It accomplishes this by boosting sodium, water, and vascular tone absorption.
- Angiotensinogen is a protein generated in the liver and circulating in the bloodstream.
- Aldosterone causes the kidneys to retain sodium and water, which helps to raise blood volume.
- Increased blood volume aids in the elevation of blood pressure.
Sample Questions
Ques. Describe the renin-angiotensin system. (3 marks)
Ans. The juxta glomerular cells release renin when the glomerular blood pressure drops. Angiotensin is converted by renin into angiotensin I and then angiotensin II.
- Angiotensin II raises glomerular blood pressure, which raises the rate of glomerular filtrate production (GFR).
- At the same time, angiotensin II stimulates the release of aldosterone by the adrenal cortex.
- Aldosterone promotes sodium ion and water reabsorption from DCT. GFR also rises as a result of this.
Ques. What role does renin-angiotensin play in the control of kidney function. (4 marks)
Ans. When the Juxta-Glomerular Apparatus (JGA) is activated by a decrease in glomerular blood pressure/flow, renin is released. Angiotensinogen in the blood is converted to angiotensin I, which is then converted to angiotensin II by renin.
- Angiotensin II is a potent vasoconstrictor, it raises glomerular blood pressure and thus the Glomerular Filtration Rate (GFR).
- It also instigates the excretion of aldosterone from the adrenal cortex.
- Aldosterone causes Na+ and water to be reabsorbed from the tubule's distal portions.
- Blood pressure and GFR both rise as a result of this.
- The Renin Angiotensin Aldosterone System (RAAS) is the name given to this complex process.
Ques. What is the renin-angiotensin-aldosterone system's (RAAS) purpose. (2 marks)
- Lower blood pressure
- Increase heart rate
- Raise your blood pressure.
- Lower your heart rate.
Ans. Correct answer is C.
Explaination: The RAAS is responsible for a long-term increase in blood volume and arterial tone. It accomplishes this by boosting sodium, water, and vascular tone absorption.
Ques. What RAAS (renin-angiotensin-aldosterone system) component is made and located in the liver, and is activated by renin. (2 marks)
- Aldosterone
- Angiotensin I
- Angiotensinogen
- Angiotensin II
Ans. C is the correct answer.
Explaination: Liver produces the Angiotensinogen protein and it circulates in the bloodstream. Angiotensinogen is then cleaved into angiotensin I by renin.
Ques. What part of the renin-angiotensin-aldosterone system does ACE play. (2 marks)
- It causes angiotensinogen to convert to angiotensin I.
- It induces renin to be released by kidney cells.
- It causes angiotensin II to stimulate the production of aldosterone by the adrenal glands.
- It is responsible for the conversion of angiotensin I to angiotensin II.
Ans. D is the correct answer.
Explaination: Renin cleaves a 10-amino-acid peptide from the N-terminus of angiotensin (which is continually generated by the liver) to yield angiotensin I. (inactive). Angiotensin-converting enzyme (ACE) further degrades angiotensin I to produce angiotensin II, the RAAS' major active peptide.
Ques. What role does aldosterone play. (2 marks)
- It causes blood vessels to tighten.
- It induces sodium and water retention in the kidneys.
- It induces potassium and water retention in the kidneys.
- It makes the kidneys only store water.
Ans. B is the correct answer.
Explaination: Aldosterone causes the kidneys to retain sodium and water, which helps to raise blood volume. Increased blood volume aids in the elevation of blood pressure.
Ques. What gland secretes antidiuretic hormone (ADH) when the renin-angiotensin-aldosterone pathway is activated. (2 marks)
Ans. Potassium is secreted into the tubules, becomes part of urine, and is expelled in exchange for sodium being reabsorbed into the circulation. Antidiuretic hormone (ADH), also known as vasopressin, is released in response to angiotensin II. The hypothalamus produces the ADH and releases it from the posterior pituitary gland.
Ques. What is the difference between rennin and renin. (3 marks)
Ans. Rennin is an enzyme also known as chymosin synthesized by the key cell of the stomach in some ruminant animals such as calves. It helps in the digestion of milk.
- The human kidney produces renin enzyme which is a part of the renin-angiotensin-aldosterone system (RAAS) hormone in the body that helps in managing the blood pressure level and fluid balance.
- It reacts with the angiotensinogen and leads to the production of angiotensin I which balances blood pressure in arteries.
Ques. State any four functions of the Renin-Angiotensin system. (4 marks)
Ans. Functions of the Renin-Angiotensin system are:
- The construction of the resistance vessels helps in an increased arterial pressure and systemic vascular resistance.
- Increases the body's water retention by stimulating salt delivery at various renal tubular sites.
- Increases liquid retention by the kidneys by stimulating the release of vasopressin from the posterior pituitary.
- Optimizes sympathetic adrenergic activity by releasing norepinephrine from sympathetic nerves and preventing norepinephrine absorption.
Ques. What are the importances of the Renin-Angiotensin system's importance. (5 marks)
Ans. The importances are:
- The renin-angiotensin system regulates and maintains blood pressure in the cells.
- When a person's blood pressure drops or rises, this system responds by releasing renin into the bloodstream.
- In the treatment of heart failure and hypertension, manipulative treatments play a crucial role.
- ACE inhibitors and receptor blockers are used to reduce arterial blood pressure, blood volume, ventricular afterload, and ventricular preload, as well as vascular hypertrophy and reverse cardiac failure.
- Dual blockade employing a combination of Angiotensin II Receptor Blockers and Angiotensin-converting enzyme I inhibitors, or therapeutic methods such as direct renin inhibition with aliskiren, a recently approved hypertension therapy.
Ques. How the process of angiotensin controlled? (3 marks)
Ans. The kidneys recognize a drop in blood pressure and a decrease in salt content, and they both trigger an increase in the renin-angiotensin mechanism. Moreover, renin synthesis is stimulated by a low heart rate, and this increases the conversion of angiotensin II to angiotensin I, and so on, by the sympathetic nervous system.
- Thyroxine, cortisol, and estrone are a few hormones that can activate the Renin-Angiotensin system.
- Both the neurological and circulatory systems generate natriuretic hormones, which can obstruct the Renin-Angiotensin pathway and increase the amount of salt lost during urination.
Read Also:
Comments