Micturition is carried out by a reflex.

Answer

### Step-by-Step Solution:

1. **Understanding Micturition**: Micturition refers to the process of expelling urine from the urinary bladder. It is a vital bodily function that involves both involuntary and voluntary actions.

2. **Formation of Urine**: Urine is formed in the kidneys through a process called filtration, which occurs in the nephron, the functional unit of the kidney.

3. **Storage in the Urinary Bladder**: Once urine is formed, it is transported to the urinary bladder, where it is stored until it is ready to be expelled.

4. **Role of the Central Nervous System (CNS)**: The urinary bladder can hold urine until a signal is sent from the CNS, which is responsible for voluntary control over micturition.

5. **Stretch Receptors**: As the bladder fills with urine, stretch receptors in the bladder wall detect the increase in volume. These receptors send signals to the CNS indicating that the bladder is full.

6. **Motor Response**: In response to the signals from the stretch receptors, the CNS sends motor messages back to the bladder. This initiates contractions of the smooth muscles in the bladder wall.

7. **Relaxation of the Urethral Sphincter**: Along with the contraction of the bladder muscles, the motor messages also cause relaxation of the urethral sphincter, which is a muscle that controls the release of urine.

8. **Expulsion of Urine**: The combination of bladder contraction and sphincter relaxation leads to the expulsion of urine from the bladder through the urethra. This entire process is known as the micturition reflex.

9. **Conclusion**: Therefore, micturition is indeed carried out by a reflex known as the micturition reflex, which involves both the CNS and the urinary system.