Functioning of the kidney is regulated by hypothalamus, juxtra glomerular apperatus (JGA) and heart.
Osmorecepters are present in hypothalamus High concentration of body fluid activates these osmoreceptors to release Antidiuretic hormone (ADH) from neurohypophysis. ADH increases permeability of renal tubules for absorption of water. This prevents excess loss of water from body. Increased volume of body of body fluid suppresses these osmoreceptors and thus ADH secretion is suppressed. ADH also constricts blood vessels and increases blood pressure. This results in increase in Glomerular filtration rate (GFR).
JGA - A fall in GFR or glomerular blood pressure activates JG cells to release REnin. IT converts angiotensinogen of blood to angiotensin. Angiotensin converting enzyme (secreted by lungs) cnverts Angiotensin I to Angiotensin II.
Angiotensin II is vasoconstrictor and also stimulates adrenal cortex to secrete aldosterone. It increases blood pressure and GFR.
An increase in blood flow to atria of the heart can cause secretion of the atrial natriuretic factor (ANF). ANF causes vasodilation and decreases blood pressure. So, checks Renin-angiotensin mechanism.
The renin-angiotensin activates the renal retention of fluid so that a fall in blood volume gets compensated. High blood volume is responsible for increase in water excretion which may be due to increased excretion of Na+ in the urine. It is known as natriuresis.
Increased Na+ excretion results in decline in aldosterone secretion. Hormone (factor) which stimulates natriuresis (antagonistic to aldosterone) and promotes Na+ and water excretion in the urine is Atrial Natriuretic Factor or hormone (ANF). Its secretion is in response to rise in blood volume.
The atria of the heart have been shown to produce ANF hormone. It it responsible for lowering of blood volume and blood pressure by promoting salt and water excretion in the urine.
Uremia - Normal value of urea in blood is 0.01 to 0.03%, but when the level rises to above 0.05% then it is called uremia. It is highly harmful and it may lead to kidney failure.
Nephritis or glomerulornephritis or Bright's disease is the term used for diseases that primarily involve renal glomeruli like haematuria, proteinuria, hypertension, oedema and oligouria.
Streptococcal glomerulornephritis is common form seen mostly in children of 6 to 16 years. It is due to infection of throat called streptococcal pharyngitis.