Regulation Of Kidney Function: Structure, Flow Chart, Regulation

Why Kidney Regulation Is Important?

Kidney regulation refers to the coordinated control of filtration, reabsorption, secretion, and hormonal signals that keep the body’s internal environment stable. It ensures that fluids, ions, and wastes are adjusted precisely according to the body’s needs.

• It helps keep the right amount of water and ions (like Na⁺, K⁺, and Cl⁻) in the body for normal cell and organ function.

• The kidneys regulate blood volume and release hormones like renin to keep blood pressure within a healthy range.

• They remove metabolic wastes, toxins, and drugs to prevent their harmful buildup in the body.

• By controlling pH, osmolarity, and fluid levels, kidneys create a stable internal environment essential for survival.

Excretory System Overview

The kidneys are some of the most important organs of the body. They serve to filter all the blood to remove waste products and excess fluids, as well as maintain fluid and electrolyte balance and perform many other functions.

Each kidney contains about one million functional units called nephrons within the nephrons, the actual filtering process occurs along with secretion and reabsorption. Apart from that, kidneys also help in maintaining blood pressure and the number of red blood cells and control the body's acid-base status.

Control of Kidney Function

The regulation of kidney function is a complicated process to ensure that the kidneys produce effective filtration of blood and also maintain the internal environment of the surroundings of the body. Mechanisms involved in this regulation are renal, neural, and hormonal, that is intrinsic renal processes.

Hormonal Regulation of Kidney Function

The hormonal regulation of kidney function includes:

Regulation via Hypothalamus

This is a part of the brain that is involved in the functions regulating the kidney through the release of a set of different hormones. An important hormone in this system is Antidiuretic Hormone, more commonly known as vasopressin.

Antidiuretic Hormone (ADH)

The hypothalamus detects changes in blood osmolarity and, in high osmolarity conditions, releases ADH from the posterior pituitary. It increases water reabsorption in the kidney, reducing urine output and returning blood osmolarity to normal by dilution.

Renin-Angiotensin-Aldosterone System (RAAS)

In response to the decrease in blood pressure, the juxtaglomerular cells secrete the enzyme renin, which will give rise to a renin-angiotensin-aldosterone cascade. Angiotensin II is a strong vasoconstrictor and mediates the release of aldosterone from the adrenal cortex. Aldosterone increases the reabsorption of sodium, and its reabsorption increases water reabsorption, which will then increase the blood.

Renal & Tubular Regulation Mechanisms

The renal and tubular regulation mechanisms are discussed below:

Juxtaglomerular Apparatus (JGA)

The juxtaglomerular apparatus is the structure in the kidney critical in increasing blood pressure and filtration rate. It is mainly composed of juxtaglomerular cells, the macula densa, and extraglomerular mesangial cells.

Tubuloglomerular Feedback

The macula densa cells of JGA can sense the alteration in the concentration of sodium chloride in the filtrate. In the event of a decreased concentration of Na+, the macula densa can cause juxtaglomerular cells to secrete renin in circulation, which alters the level of filtration and reabsorption in Na+.

Additional Kidney Regulation Factors

These additional regulatory factors help maintain homeostasis during stress, dehydration, or changes in blood pressure.

Sympathetic neural control: It constricts renal blood vessels during stress, reducing GFR and conserving fluid for essential organs.

Blood volume and pressure: Changes in blood volume or pressure directly alter GFR, prompting the kidneys to adjust urine output to restore balance.

Osmolarity of interstitial fluid: The solute concentration in the renal medulla influences water movement, helping regulate urine concentration and overall fluid balance.

Regulation of Kidney Function NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Hormonal regulation of Kidney Function

• Renal and Tubular Mechanism

Practice Questions for NEET

Q1. Assertion: Renin-angiotensin-aldosterone (RAAS) regulation of blood pressure and kidney function is essential.

Reason: When there is a drop in blood pressure or blood volume, the RAAS is triggered.

1. Assertion and reason are both true, and reason is the correct explanation of assertion.

2. Both assertion and reason are accurate, but reason is not the correct explanation of assertion.

3. The assertion is correct, but the reasoning is incorrect.

4. Both the assertion and reason are incorrect.

Correct answer: 1) Assertion and reason are both true, and reason is the correct explanation of assertion.

Explanation:

Both the claim and the justification are true. The complex RAAS system is essential for controlling kidney and blood pressure function. It becomes active when there is a drop in blood pressure or blood volume, which causes the kidneys to release renin. Angiotensinogen is then transformed into angiotensin I, which is then changed into angiotensin II by the action of renin. Angiotensin II increases blood vessel constriction, which raises blood pressure, and stimulates aldosterone release, which encourages sodium ion reabsorption in kidney tubules. In the end, this aids in preserving the body's fluid balance and blood pressure.

Hence, the correct answer is an option (1) Assertion and reason are both true, and the reason is the correct explanation of assertion.

Q2. What is the primary function of the JGA [juxtaglomerular apparatus] in the human body?

1. Regulating blood pressure

2. Digesting food

3. Synthesizing hormones

4. Maintaining body temperature

Correct answer: 1) Regulating blood pressure

Explanation:

The JGA (juxtaglomerular apparatus) is a group of specialized cells found in the kidney that plays a crucial role in regulating blood pressure. The primary function of JGA is to monitor the blood pressure and sodium levels in the blood and adjust the release of renin, a hormone that helps regulate blood pressure. When blood pressure is low, JGA releases renin, which triggers a series of chemical reactions that result in the production of angiotensin II, a powerful vasoconstrictor that narrows the blood vessels and raises blood pressure. Therefore, JGA helps maintain blood pressure within a healthy range, which is essential for optimal organ function and overall health.

Hence, the correct answer is Option 1) Regulating blood pressure.

Q3. A decrease in blood pressure/volume will not cause the release of:

1. Renin

2. Atrial Natriuretic Factor

3. Aldosterone

4. ADH

Correct answer: 2) Atrial Natriuretic Factor

Explanation:

ANF is an atrial natriuretic factor that causes vasodilation and leads to a decrease in blood pressure. The increase in the blood flow to the atria of the heart causes the release of ANF. It is mainly released by the atria of the heart in response to high blood volume. It reduces the water, sodium, and adipose concentration in the circulatory system and thus reduces blood pressure.

Hence, the correct answer is option 2) Atrial Natriuretic Factor.

Also Read:

• MCQs on Regulation of Kidney Function

• Ultrafiltration

• Hemodialysis

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