The process of release of urine is called micturition and the neural mechanism causing it is called the micturition reflex.
The urinary bladder and the internal sphincter are supplied by sympathetic and parasympathetic nervous systems of autonomic nervous system. In response, the Stretch receptors on the walls of the bladder send signals to the Central Nervous System (CNS).
The CNS passes on motor messages to initiate the contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincter causing the release of urine.
Disorders of excretory system includes
(i) Uremia It is the malfunctioning of kidneys, which leads to accumulation of urea in blood in turn the kidney faliure. In such patients urea can be removed by haemodialysis.
(ii) Renal Failure (RF) It is caused by a decrease in glomerular filteration. in Acute Renal Failure (ARF) both kidneys abruptly stop working due to damaged renal tubules, kidney stones, antibiotics, etc. Haemodialysis and renal transplant are the only ways to auruve overcome renal failure.
(iii) Renal Calculi It is the formation of stones or insoluble mass of crystallised salts in the kidney.
(iv) Glomerulonephritis It is the inflammation of glomeruli of kidney.
