'Human paranasal sinuses have been shown to have higher volumes in individuals living in warmer climates, and thus may be considered radiators of the brain'
By Pat Kelly. US Researchers have claimed that we yawn not because of fatigue or boredom, but as a reflex action to cool an overheated brain.
The team from the University of Maryland and Yale University hypothesised that excessive yawning is a symptom of increased brain temperature. This, they said, could be as a result of a damaged central nervous system or possibly a prelude to a migraine or even an epileptic seizure.
In the study — published in the newly-resurrected journal Medical Hypotheses — they observed that mucus within the sinus is constantly evaporating to cool cerebrospinal fluid and blood vessels. Yawning, by opening the sinuses, facilitates this process further by opening the sinuses on either side of the nose.
“The function of the paranasal sinuses has been a controversial subject since the time of Galen,” the authors said. “Human paranasal sinuses have been shown to have higher volumes in individuals living in warmer climates, and thus may be considered radiators of the brain.
“The present authors hypothesise that the thin posterior wall of the maxillary sinus may flex during yawning, operating like a bellows pump, actively ventilating the sinus system, and thus facilitating brain cooling,” they commented.
“Such a powered ventilation system has not previously been described in humans, although an analogous system has been reported in birds.”
The study can be accessed at http://www.sciencedirect.com/science/article/pii/S0306987711004142.
pat.kelly@imt.ie
About Pat Kelly
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