Regulation of Kidney Function Notes Class 11 (original) (raw)
Last Updated : 23 Jul, 2025
The Kidneys which are present in the human body are responsible for multiple functions in humans which include the formation of urine, water metabolism, ionic balance, and regulation of blood pressure. Therefore with the help of these kidneys, the wastes are being removed from human body. These kidneys are responsible for regulating water balance in human beings and also filtering waste and excess of these fluids from the blood.
Human Excretory System
A human excretory system consists of:
- **Kidneys: Human body consists of two Kidneys which are bean-shaped structures and are reddish brown in color. They are situated between the last thoracic and lumbar vertebra. In each kidney, there consists of a notch in the inner side which is known as hilum. From this hilum, the nerves and ureter blood vessels enter.
- **Ureters: They are the tube-like structure that carries out urine from the kidney to the urinary bladder. There is a pair of ureters which are attached to each kidney.
- **Urinary Bladder: It is a hollow organ in the lower part of the abdomen which is a temporary storage of urine.
- **Urethra: They are a normal tube-like structure that carries out the urine from the urinary bladder to outside the human body.
Regulation of Kidney Function
The Kidney function is regulated by the hormonal feedback mechanism which involves hypothalamus regulation, regulation involving Juxtaglomerular Apparatus (JGA), and to some extent, the heart. If there is a change in blood volume, fluid volume or ionic concentration it activates the hypothalamic osmoreceptors whereas if there is excessive fluid loss or an increase in blood pressure these osmoreceptors respond by stimulating the neurohypophysis which further secrete ADH.
Main Hormones that Regulate Kidneys
The Juxtaglomerular Apparatus(JGA)
The regulation of Juxtaglomerular Apparatus(JGA) is also called the Angiotensin mechanism. Whenever the blood flow in the glomerulus decreases, renin is also released from juxtaglomerular cells. By the renal sympathetic nerves renin levels are increased through a direct action on granular cells and a decrease in the flow to the macula densa. When there is increased in renal sympathetic nerve activity it causes drop in the GFR which gradually increase the water reabsorption and proximal sodium ions. This results in reduction of fluid in the macula densa which later on helps in the renin production at high level. The Juxtaglomerular apparatus responds to decrease in blood pressure.
The Renin-Angiotensin-Aldosterone System (RAAS)
Angiotensin is an enzyme, it is located in the endothelium which is used to convert angiotensin I to angiotensin II. In the cardiovascular system angiotensin II stimulates vasoconstriction. The cardiovascular system further stimulates aldosterone production in the adrenal glands which increase the sodium reabsorption in the kidneys. **The RAAS is responsible for basic regulation of blood pressure.
Hypothalamus
Antidiuretic Hormone (ADH) or Vasopressin
From neurohypophysis the Antidiuretic hormone or vasopressin are released if the osmoreceptors are activated. These are activated when there is a change in blood pressure or there is an excessive loss of fluids. Antidiuretic hormone stimulates the reabsorption of water from the distal parts of the tubules hence this prevents water loss and diuresis whereas when there is sufficient body fluid these osmoreceptors are switched off and therefore the release of ADH is suppressed. This ADH causes constriction of blood vessels which results in **increase of blood pressure which further increases the flow of blood in the glomerulus.
Atrial Natriuretic Peptide (ANP)
Atrial Natriuretic Peptide is a 28 amino acid peptide hormone which are located in the granules in atrial myocytes. ANP is released when there is increased blood flow in the atria of the heart. Renal tubules are inhibited from reabsorbing water and salt. The reduced sodium ion and the water level enhance the urine result, allowing the blood volume to become normal. ANP exerts moderate effects in vasodilatory which results in **low blood pressure but increase in capillary pressure.
Micturition
Micturition is defined as a process where urine is expelled out (passed out) from the human body. The urine which are formed in the nephron is stored in the urinary bladder until a voluntary signal is given by the CNS which involves contraction of soft muscles of the urinary bladder and relaxation of urethral sphincter which causes release in urine.
Disorders of Excretory System
Some of the disorders which are related to excretory system are mentioned below:
- Uremia: It is a type of disorder in which urea is accumulated in the blood due to malfunctioning of kidneys which can lead to kidney failures. Through the process of hemodialysis this disorder is being treated.
- Renal failure: In this condition the glomerular filtration and both the kidneys stops working. Kidney transplant is the only treatment available in this disorder.
- Renal Calculi: It is a condition in which stones salts are formed in the kidney. By operation this disorder can be cured.
- Glomerulonephritis: In this condition there is an inflammation of glomeruli happens which occurs due to the entry of protein and RBCs.