Non-breathing air movements – used to clear air passages, express emotions, or in the case of hiccups, there is no useful function at all.
Coughing
– clears the lower respiratory passages
Sneezing
– clears the upper respiratory passages
Laughing/crying
– express emotions
Yawning
– aids in oxygenation of the blood by ventilating a large proportion of the alveoli
Speech
– communication
Control of Breathing
The respiratory center is a poorly defined area of the brain stem. There are two parts of the respiratory center :
Rhythmicity area of the medulla
: two groups of neurons that extend the length of the medulla. One group, the dorsal respiratory group controls the basic rhythm of breathing. The other group is the ventral respiratory group, which becomes active in forceful breathing.
Pneumotaxic area of the pons
: these neurons regulate the impulses from the dorsal respiratory group, and so control the rate of breathing.
Chemosensitive areas in the respiratory center will also exert control over breathing. These areas are located near the vagus nerve origins in the ventral part of the medulla. They detect changes in CO2 and H+ concentrations.
If the concentration rises, the chemosensitive area sends a signal to the respiratory center to breathe faster and/or deeper
Oxygen concentrations are detected by chemoreceptors in the carotid and aortic bodies (located in the carotid artery and aorta, respectively). These receptors are less sensitive than those that sense CO2 and H+.
The inflation reflex regulates the depth of breathing. Stretch receptors (mechanoreceptors) are found in the visceral pleura, bronchioles and alveoli. If the lungs are being overstretched, impulses are sent to the pneumotaxic center to shorten inspiration duration.
Conscious control can be exerted, to a point. This is called cortical control.
Hypothalamic controls
involve the sympathetic nervous centers of the hypothalamus. Fear, anger, "sucking air" in disgust, all are considered hypothalamic in nature.