The impulse for voluntary muscles during forced breathing starts in ...............

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks where the impulse for voluntary muscles during forced breathing originates. This indicates that we need to identify the part of the nervous system responsible for controlling voluntary muscle movements during the act of forced breathing.

2. **Identifying the Role of the Respiratory System**: The respiratory system is primarily responsible for gas exchange, which involves obtaining oxygen and removing carbon dioxide. This process requires ventilation of the lungs.

3. **Distinguishing Between Tidal and Forced Breathing**: Tidal breathing is the normal, relaxed breathing that primarily involves the diaphragm. In contrast, forced breathing requires additional muscle involvement, such as the intercostal muscles and abdominal muscles, which are classified as voluntary muscles.

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