Which Event Occurs First

Question

Which event occurs first?
A) The diaphragm contracts.
B) Air moves into the lungs.
C) The phrenic nerve fires.
D) The inspiratory neurons in the medulla fire.

Accepted Answer

The inspiratory neurons in the medulla fire first, triggering the breathing process. The phrenic nerve then sends signals to the diaphragm to contract, which creates a vacuum and allows air to be drawn into the lungs. Therefore, D is the correct answer.