Micturition is carried out by a reflex.

Answer

### Step-by-Step Text Solution:

1. **Understanding Micturition**: Micturition, commonly known as urination, is the process of expelling urine from the urinary bladder through the urethra.

2. **Role of the Nervous System**: Micturition is controlled by the nervous system, specifically through a reflex action. This means that the process does not require conscious thought and is instead an automatic response.

3. **Sensory Neurons and Reflex Arc**: When the bladder fills with urine, stretch receptors in the bladder wall are activated. These sensory neurons send signals to the spinal cord rather than directly to the brain. This is important because it allows for a quicker response.

4. **Spinal Cord Processing**: The signals from the bladder synapse in the spinal cord, where they are processed. This reflex action allows for faster responses because it bypasses the brain, which would take longer to process the information.

5. **Activation of Motor Neurons**: The spinal cord then activates spinal motor neurons that control the muscles involved in micturition. This includes the detrusor muscle of the bladder, which contracts to push urine out.

6. **Relaxation of Sphincters**: Concurrently, the internal and external sphincters (muscles that control the release of urine) relax, allowing urine to flow from the bladder into the urethra.

7. **Conclusion**: Therefore, micturition is indeed a reflex action that is primarily mediated by the spinal cord, with input from the brain to coordinate the process.