Regulation of urine formation - class-IX

The juxtaglomerular apparatus is a type of endocrine organ that is small in size, located within kidneys and helps in the regulating the function of nephrons. This is mainly  involved in the secretion of renin and erythropoietin in response to changes in the renal blood pressure or blood flow. 

When someone drinks lot of water which is excess amount for his body, as a result osmolarity of the blood will decreases.The decrease in osmolarity will suppress the release of ADH. Correct option is (A).

Vasopressin, also known as antidiuretic Hormone (ADH) is a hormone synthesized in the hypothalamus and stored in the posterior pituitary glands. It absorbs water from renal tubule thereby conserving water in our body. It constantly regulates and balances the water level of the body. Osmotic sensors and baroreceptors join with ADH in water metabolism.

• Diabetes insipidus is a rare disorder that occurs when a person's kidneys pass an abnormally large volume of urine that is insipid dilute and odourless.
• People with diabetes insipidus have normal blood glucose levels; however, their kidneys cannot balance fluid in the body. 
• Hence, the Urine of a human being suffering from diabetes insipidus is Tasteless and watery.
• So, the correct answer is 'Tasteless and watery'.

Over 180 liters of urine is produced in the human body every day. Out of this, only 1.5 liters is actually excreted. This means that 99% of the urine produced is reabsorbed in the body. Various solutes are absorbed in different parts of the renal tubule. Maximum water absorption takes place in the proximal convoluted tubule. 

Antidiuretic hormone or ADH ( also known as vasopressin ) is involved in reabsorption of water in kidney. Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation. In the absense of antidiuretic hormone, the collecting ducts are virtually impermiable to water, and it flows out as urine.

The maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations. is called Osmoregulation. It  is carried out by 'anti-diuretic hormone'. 

Vassopressin or anti-diuretic hormone helps prevent loss of water from the body by increasing the reabsorption of water from the kidney and making urine more concentrated. It is also responsible for increasing the blood pressure by constricting the blood vessels. So, the correct option is 'increasing blood pressure'.

The proximal convoluted tubule is the primary site for the reabsorption of bicarbonate and the secretion of hydrogen ions, which contributes to the acidification of urine.

A. Renin is an aspartic protease protein as well as an enzyme which is secreted by the kidneys in the Renin-angiotensin-aldosterone system that regulates the arterial blood pressure.

The urinary bladder stores urine collected from the ureters and expels it to the exterior through the urethra, which represents the terminal opening and passage of the urinary tract.

ADH is anti diuretic hormone. It is secreted from posterior pituitary. It stimulates water absorption and hence reduces urine volume.

Glomerular filtration rate (GFR) is driven by net filtration pressure. Compression of the renal capsule increases hydrostatic pressure in the Bowman space, which opposes filtration and thus decreases GFR.

Drinking sea water increases blood osmolarity due to its high salt concentration, which strongly stimulates osmoreceptors in the hypothalamus to secrete antidiuretic hormone (ADH) to conserve water. Distilled water would lower osmolarity and decrease ADH secretion, while isotonic water causes little change.

Kidneys play a very large role in human osmoregulation by regulating the amount of water reabsorbed from glomerular filtrate in kidney tubules, which is controlled by hormones such as antidiuretic hormone(ADH), aldosterone and corticotropin. 

When the level of water in blood goes up for example in cold or when we had a lot to drink, the hypothalamus detects the change and sends a message to the pituitary. The release of ADH into the blood is slowed down or even stopped. Without ADH the kidneys will not save as much water and we produce large volumes of dilute urine. The level of water in the blood falls back to the normal level.

The reabsorption of water in the earlier parts of the nephron (regardless of a person's state of hydration), independent of ADH is termed as 'obligatory reabsorption of water', whereas the water reabsorption in the distal part of the nephron (in accordance with the body's state of hydration), under the influence of ADH, is termed as 'facultative reabsorption of water'.
In facultative reabsorption, the collecting ducts become more permeable to water due to the effect of ADH, so water is reabsorbed by osmosis. Osmosis is a passive process (the diffusion of water from an area of higher water concentration to an area of lower water concentration), no expenditure of ATP energy is required in it.
Thus water reabsorption under the influence of ADH is facultative and passive reabsorption.

The primary hormone involved in regulating water loss is the antidiuretic hormone (ADH). When the body has excess water, cells in the hypothalamus of the brain respond and send a signal to the pituitary and only a small amount of ADH is released and water is lost. When we are dehydrated these same brain cells cause more ADH to be released and water leaves the collecting duct and is returned to the blood. Thus reducing the volume of urine. Adrenocortico hormones are secreted by adrenal cortex under the influence of adrenocorticotropic hormone. The major adrenal cortex enzymes are mineralocorticoids and glucocorticoids. The mineralocorticoids act on kidney tubules and help in maintaining sodium and potassium balance.

Vasopressin also known as antidiuretic hormone (ADH), is a neurohypophysial hormone found in most mammals. Its two primary functions are to retain water in the body and to constrict blood vessels. Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation. In the absence of antidiuretic hormone, the collecting ducts are virtually impermeable to water, and it flows out as urine. 

When renal blood flow is reduced, juxtaglomerular cells in the kidneys convert the prorenin present in the blood into renin and secrete it directly into circulation. Plasma renin then carries out the conversion of angiotensinogen released by the liver to angiotensin I. Angiotensin I is subsequently converted to angiotensin II by the enzyme angiotensin-converting enzyme found in the lungs. Angiotensin II is a potent vasoactive peptide that causes blood vessels to constrict, resulting in increased blood pressure.

ADH targets nephrons in kidney to increase water reabsorption and thereby decreasing water content in urine. Inability of neurohypophysial system to produce ADH, causes excess urine production with resultant ion loss from blood. This condition is known as diabetes insipidus (watery urine). 

Osmoreceptors in the body are activated by changes in blood volume, body fluid volume and ionic concentration. An excessive loss of fluid from the body can activate these receptors, which stimulate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis. ADH facilitates water reabsorption from latter parts of the tubule (Distal convoluted tubule and Collecting duct), thereby preventing diuresis. An increase in body fluid volume can switch off the osmoreceptors and suppress the ADH release to complete the feedback. ADH mainly acts on collecting ducts of kidney and increase the water reabsorption in this part.

Vasopressin (ADH) is a peptide hormone, secreted from the posterior pituitary, increases water permeability of the kidney's collecting duct and distal convoluted tubule by inducing translocation of aquaporin-CD water channels in the collecting duct plasma membrane. Thus, increases the water absorption in the collecting duct and helps in water retaintion in the body.

ADH regulates the water balance in body by decreasing the excretion of free water from kidney (antidiuretic effect). It does so by increasing the permeability of ADH responsive cells in linings of distal convoluted tubules and collecting ducts of renal nephrons. 

Anti-diuretic hormone or the vasopressin is secreted by the hypothalamus and is stored and released by the posterior pituitary. This hormone is responsible for maintaining blood volume. When salty food is consumed, it increases the ions in the bloodstream and reduces the volume of the blood. The ADH will be released in this condition, that will directly act on the water reabsorbing channels in the collecting ducts of the nephrons. So, water will be reabsorbed from the filtrate and restored back to the blood. 

Diabetes insipidus is a rare condition that occurs when the kidneys are unable to conserve water during the process of filtering blood. Diabetes insipidus is caused by a lack of antidiuretic hormone (ADH), also called vasopressin, which prevents dehydration, or the kidney's inability to respond to ADH. ADH enables the kidneys to retain water in the body. The hormone is produced in the hypothalamus. It is stored and released from the pituitary gland.

ADH is secreted by pituitary gland. It increases the water permeability of distal convoluted tubules and collecting tubules, hence, plays a significant role in water re-absorption. The absence of ADH will reduce water reabsorption which may lead to water diuresis or diabetes insipidus.

Renin is an enzyme secreted by the kidneys that converts angiotensinogen into angiotensin I, which is a key step in the renin-angiotensin-aldosterone system.

 A fall in glomerular blood flow/glomerular blood pressure/GFR can activate the JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II. Angiotensin II, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. Angiotensin II also activates the adrenal cortex to release Aldosterone. Aldosterone causes reabsorption of Na+ and water from the distal parts of the tubule. This also leads to an increase in blood pressure and GFR. This complex mechanism is generally known as the Renin-Angiotensin mechanism. Hence Angiotensin  II and aldosterone regulate solute reabsorption during urine formation.

Aldosterone is the hormone produced by the adrenal gland. Aldosterone balance sodium and potassium in our body. When Excess of aldosterone is produced by the adrenal gland causes the body to lose potassium and retain sodium. It leads to excretion of dilute urine.

During the summer season, The hormone whose concentration is maintained at a high level is Vasopressin or ADH(antidiuretic hormone). When excess water is lost through urine the blood volume is decreased and its osmolarity is increased which stimulates the posterior pituitary to release ADH.ADH decreases the volume of urine by increasing the reabsorption of water by kidneys and prevents diuresis. Hence it is also called antidiuretic hormone.

The term diuresis refers to the excessive production of urine. When excess water is lost through urine the blood volume is decreased and its osmolarity is increased which stimulates the posterior pituitary to release ADH.ADH decreases the volume of urine by increasing the reabsorption in the later parts of the tubule and prevents diuresis. 

When excess water is lost through urine the blood volume is decreased and its osmolarity is increased which stimulates the posterior pituitary to release ADH. ADH decreases the volume of urine by increasing the reabsorption of water by kidneys and prevents diuresis. Thus ADH takes part in reabsorption of water.

When excess water is lost through urine the blood volume is decreased and its osmolarity is increased which stimulates the posterior pituitary to release ADH.ADH decreases the volume of urine by increasing the reabsorption by kidneys and prevents diuresis. Hence when someone drinks a lot of water, ADH release is suppressed.

The term diuresis refers to the excessive production of urine. When excess water is lost through urine the blood volume is decreased and its osmolarity is increased which stimulates the posterior pituitary to release ADH.ADH decreases the volume of urine by increasing the reabsorption by kidneys and prevents diuresis. Hence it is also called antidiuretic hormone.

The hormone ADH (vasopressin) is released from the neurohypophysis (posterior pituitary gland). ADH is synthesized by the hypothalamus and stored in the neurohypophysis. When blood volume is decreased or sodium concentration of blood is increased due to dehydration the ADH is released from the neurohypophysis. ADH causes retention of water by kidneys and maintains blood volume.

When excess water is lost through urine the blood volume is decreased and its osmolarity is increased which stimulates the posterior pituitary to release vasopressin. Vasopressin(ADH) decreases the volume of urine by increasing the facultative absorption of water by kidneys and prevents diuresis. Hence facultative absorption of water from primary urine is influenced by the hormone vasopressin.

When excess water is lost through urine the blood volume is decreased and its osmolarity is increased which stimulates the posterior pituitary to release Vasopressin. Vasopressin(ADH) decreases the volume of urine by increasing the facultative absorption of water by kidneys and prevents diuresis. ORS (oral rehydration salt) replaces the lost fluids and essential salts, prevent dehydration and maintain blood volume. Hence Intake of ORS inhibits secretion of vasopressin.

The juxta glomerular apparatus is a specialised structure made by the glomerular afferent arteriole and the distal convoluted tubule.It is located near the vascular pole of the glomerulus .The main function of juxta glomerular apparatus is to regulate the filteration rate of glomerulus and blood pressure of the body. 

When GFR falls, the juxtaglomerular cells in the kidney detect the change and release renin to activate the RAAS pathway, which helps restore blood pressure and GFR.

Antidiuretic hormone (ADH) is also known as vasopressin because of its ability to cause vasoconstriction and raise blood pressure at high concentrations, in addition to its primary role in water reabsorption in the kidneys.

Angiotensinogen is a plasma protein produced and released into the circulation by the liver cells. It is also known as renin substrate. It is the component of the renin-angiotensin system, a hormone system which regulates blood pressure and fluid balance. So, the correct answer is 'Liver cells'.

About $0-80%$ of the glomerular filtrate is reabosrbed in the proximal convoluted tubule (PCT). Glucose, amino acids, vitamins, hormones, sodium, potassium, chlorides, phosphates, bicarbonates, much of water and some urea are reabsorbed from the filtrate. 

A comparison of the volume of the filtrate formed per day ($180$ litres per day) with that of the urine released ($%1.5$ litres). suggests that nearly $99%$ of the filtrate is reabsorbed by the renal tubules into the blood. 

The main driving force favouring fluid filtration from the glomerular capillary to Bowman's space is glomerular capillary blood pressure($P _{GC}$). 

Antidiuretic hormone (ADH) is a hormone that helps your kidneys manage the amount of water in your body. 

Tubular reabsorption is the process by which solutes and water are removed from the tubular fluid and transported into the blood. It is called reabsorption. Reabsorption is a two-step process beginning with the active or passive extraction of substances from the tubule fluid into the renal interstitium, and then the transport of these substances from the interstitium into the bloodstream. These transport processes are driven by Starling forces, diffusion, and active transport. Some key regulatory hormones for reabsorption include: aldosterone, which stimulates active sodium reabsorption; antidiuretic hormone, which stimulates passive water reabsorption. Both hormones exert their effects principally on the collecting ducts.

ADH targets nephrons in the kidney to increase water reabsorption and thereby decreasing water content in urine. The inability of the neurohypophysial system to produce ADH causes excess urine production with resultant ion loss from the blood. This condition is known as diabetes insipidus (watery urine). This makes option A correct and option B incorrect. Since ADH regulates the urine volume, not its pH, option C is incorrect. Urochrome is the yellow pigment, derived from the breakdown of heme, which is deposited in blood and then is excreted by kidney with urine. This makes option D incorrect. The correct answer is A.

Juxtaglomerular cells are the specialized smooth muscle cells present in the walls of the afferent arterioles that go to the glomerulus. Their function is to produce an enzyme called renin when the osmolarity of blood changes. Renin converts angiotensin secreted by the liver into angiotensin$I$. This is later converted into angiotensin$II$ by an enzyme released by lungs. Angiotensin$II$ acts on adrenal glands to stimulate the release of aldosterone. Aldosterone helps in reabsorption of na+ and water from distal convoluted tubule and the concentration of Na$^+$ ions decreases in the filtrate. 

A fall in GFR can stimulate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR comes back to normal.

A) LH is Luteinising Hormone which is not involved in the concentration of urine.

Caffeine is a central nervous system stimulant of the methylxanthine
class of psychoactive drugs. It is the most mildest stimulant and is
most widely consumed psychoactive drug. It is present in coffee, tea and cola drinks.
Therefore, the correct answer is option D.

The water reabsorption in the distal part of the nephron is in accordance with the body's state of hydration, under the influence of ADH and is termed as 'facultative reabsorption of water'.  ADH is secreted in the hypothalamus of brain and released into blood stream from the pituitary gland. The collecting ducts become more permeable to water due to the effect of ADH, so more water is reabsorbed by osmosis and no expenditure of ATP energy is required. The release of ADH is triggered when osmoreceptors in the hypothalamus detect an increase in osmolarity of the blood above a set point of ${300 mosm L^{-1}}$. In this situation the osmoreceptors cells also promotes thirst. Drinking reduces the osmolarity of the blood, which inhibits the secretion of ADH.

Juxtaglomerular cells are specialized smooth muscle cells of glomerular arterioles. They synthesize, store and secrete the enzyme renin. It plays a critical role in the renin angiotensin system and thus in renal autoregulation of the kidney.