Hawaii Massage License Practice Exam

What is the primary function of the phrenic nerve?

1. Stimulate limb movement

2. Control respiratory diaphragm

3. Regulate heart rate

4. Sensory perception

The correct answer is: Control respiratory diaphragm

The primary function of the phrenic nerve is to control the respiratory diaphragm. This nerve originates in the neck (C3-C5 spinal segments) and is crucial for the proper functioning of the diaphragm, which is the main muscle involved in breathing. When the phrenic nerve stimulates the diaphragm, it contracts, creating a negative pressure in the thoracic cavity that allows air to flow into the lungs. This action is essential for normal respiration, and any impairment to the phrenic nerve can lead to difficulties in breathing. The other options involve different physiological functions: stimulating limb movement pertains to motor nerves associated with the limbs, regulating heart rate relates to the autonomic nervous system's control over heart function, and sensory perception involves sensory nerves that convey information from the environment to the brain. None of these functions are performed by the phrenic nerve, reinforcing why controlling the respiratory diaphragm is its primary and most critical role.