Breathing is primarily an involuntary activity regulated by the brainstem respiratory centers. However, it can also be consciously controlled, allowing us to hold our breath or take deeper breaths when needed. This voluntary control is facilitated by the cerebral motor cortex, which bypasses the medullary centers to stimulate the respiratory muscles directly.
However, the ability to hold one's breath voluntarily is not limitless. When the CO2 concentration in the blood reaches a critical level, the brainstem respiratory centers automatically resume breathing. This explains why drowning victims typically have water in their lungs.
In our lungs, receptors respond to a variety of irritants. These receptors communicate with the respiratory centers via the vagus nerve.
The Hering-Breuer reflex is a protective mechanism activated by stretch-sensitive receptors in the lungs' walls that activate during overinflation. This reflex inhibits further inhalation and initiates exhalation.
Various factors can influence our breathing rate and depth. Anticipation or emotional anxiety, for example, can stimulate the limbic system, leading to increased breathing rate and depth. Changes in body temperature can also impact breathing; increased temperature quickens the rate, while decreased temperature slows it down. Sudden severe pain can cause temporary apnea, while prolonged somatic pain increases the breathing rate.
