Which part of brain sends voluntary 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

To answer the question regarding which part of the brain sends voluntary motor signals to the smooth muscles of the urinary bladder when it gets filled with urine, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Urinary Bladder Function**:
- The urinary bladder is a muscular sac that stores urine. When it fills, signals are sent to the brain indicating that it needs to be emptied.

2. **Identifying the Brain Regions**:
- The options provided include the medulla, cerebellar cortex, hypothalamus, and brain stem. We need to determine which of these is responsible for sending signals to the bladder.

3. **Role of the Brain Stem**:
- The brain stem is crucial in regulating many autonomic functions, including those related to the urinary bladder. Within the brain stem, there is a specific center known as the **Pontine Micturition Center (PMC)**.

4. **Function of the Pontine Micturition Center**:
- The PMC is responsible for coordinating the process of urination. When the bladder is full, the PMC sends signals to the smooth muscles of the bladder to initiate contraction and allow for urination.

5. **Conclusion**:
- Therefore, the correct answer to the question is that the **brain stem** sends voluntary motor signals to the smooth muscles of the urinary bladder when it is filled with urine.

### Final Answer:
**Brain Stem**

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