Which part of brain sends valuntary motor signals to smooth muscles of urinary bladder when the bladder get filled with urine?

Options

A. Medulla
B. Cerebral cortex
C. Hypothalamus
D. Brain stem

Answer

### Step-by-Step Solution:

1. **Understanding the Mechanism of Urination**:
- The urinary bladder contains mechanoreceptors that detect the stretching of the bladder wall as it fills with urine.

2. **Signal Transmission**:
- When the bladder is filled, these mechanoreceptors send signals through nerves to the central nervous system (CNS).

3. **Role of the CNS**:
- The CNS processes these signals and coordinates the response needed to empty the bladder.

4. **Muscle Involvement**:
- The smooth muscles of the bladder, known as the detrusor muscle, are responsible for bladder contraction.

5. **Sphincter Control**:
- The CNS sends voluntary motor signals to relax the sphincters, allowing urine to flow out of the bladder.

6. **Brain Regions Involved**:
- The primary brain region responsible for sending these voluntary motor signals is the **pons**, specifically the **pontine micturition center**.

7. **Additional Brain Areas**:
- While the pons plays a crucial role, the **cerebral cortex** is also involved in the regulation of this process, allowing for voluntary control over urination.

8. **Conclusion**:
- Therefore, the part of the brain that sends voluntary motor signals to the smooth muscles of the urinary bladder when it is filled with urine is the **pons**, specifically the **pontine micturition center**.