Question

The outline of principal events of urination is given below in random manner.
(i) Stretch receptors on the wall of urinary bladder send signals to the CNS.
(ii) The bladder fills with urine and becomes distended.
(iii) Micturition.
(iv) CNS passes on motor messages to initiate the contraction of smooth muscles of bladder and simultaneous relaxation of urethral sphincter.

• A. (i) $\to$ (ii) $\to$ (iii) $\to$ (iv)
• B. (iv) $\to$ (iii) $\to$ (ii) $\to$ (i)
• C. (ii) $\to$ (i) $\to$ (iv) $\to$ (iii)
• D. (iii) $\to$ (ii) $\to$ (i) $\to$ (iv)

Answer 1

Answer: (C)

(ii) $\to$ (i) $\to$ (iv) $\to$ (iii)

Process of urination involves these following steps: -

1. Filling of the urinary bladder with the urine and after filling, the bladder becomes distended.
2. The filled bladder stretches the receptors present on its wall and send signals to the CNS.
3. After receiving the signal the CNS passes the signal to initiate the contraction of smooth muscles of bladder and simultaneous relaxation of the urethral sphincter.
4. Ultimately after the contraction of detrusor muscles of the urinary bladder and relaxation of the sphincter causes Micturition.

So, the correct answer is (ii) → (i) → (iv) → (iii).