Physical Therapy Assistant Practice Exam

Which nerve innervates the diaphragm?

1. C3, C4, C5

2. C5, C6, C7

3. C7, C8, T1

4. C4, C5, C6

The correct answer is: C3, C4, C5

The correct answer is based on the anatomical and physiological function of the diaphragm and the specific nerve roots that contribute to its innervation. The diaphragm is primarily innervated by the phrenic nerve, which is formed from the nerve roots C3, C4, and C5. This innervation is critical for the diaphragm's role in respiration. When the diaphragm contracts, it creates negative pressure in the thoracic cavity, allowing air to be drawn into the lungs. The significance of the contribution from each of these cervical nerve roots is that a lesion at any point along these roots can impair diaphragmatic function, potentially leading to respiratory distress. Understanding this innervation pattern is fundamental in both clinical practice and the assessment of patients with respiratory issues.