Test: Micturition and Role of other Organs in Excretion (August 24) - NEET MCQ

Stretch receptors of the urinary bladder are responsible for stretch reflex. If these are removed then autonomic nenous system control will not be there and bladder will always remain full and frequently pass urine into urethra.

In a person suffering from diabetes mellitus, degradation of fat increases resulting in the production of ketone bodies. These are acidic and poisonous and get excreted out in urine. Therefore, presence of ketone bodies in urine is an indicator of diabetes mellitus. pH of urine is 6. On an average, 25-30 gm of urea is excreted via urine daily. Contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincter causes release of urine.

ADH helps in water reabsorption, making the urine hypertonic.

Urea is a nitrogenous waste formed as a result of metabolism of various food/beverages in the body and is excreted in the urine. So, if a person is not taking food/ beverages he will have less urea in his urine.

The yellow colour of the urine is due to the presence of pigment urochrome, which is a breakdown product of haemoglobin from worn out RBCs.

The correct order of phenomena in the micturition process is as follows:

(i) Urine formed by the nephron is ultimately carried to the urinary bladder.
(ii) This signal is initiated by the stretching of the urinary bladder as it gets filled with urine.
(iii) In response, the stretch receptors on the bladder send signals to the CNS.
(iv) The CNS passes motor messages to initiate the contraction of smooth muscles of the bladder, causing the release of urine.

So, the correct order is (i), (ii), (iii), and (iv), which corresponds to Option A.

The ejection of urine involves a voluntary signal that comes from the Central Nervous System (CNS). The CNS controls and coordinates the release of urine from the urinary bladder, allowing an individual to voluntarily initiate and control the micturition process. Therefore, the correct answer is (2) CNS.