Physiologically, deep breaths and open mouths can cool the brain slightly, but the evidence that this is a real cause of yawning is not convincing. A logical but disproven theory on why we yawn is to improve oxygen in the blood or remove carbon dioxide. This seems logical since yawning does bring in more oxygen with a deep breath and the expiration removes more carbon dioxide than the usual breath, but research by putting people in low-oxygen or high- carbon-dioxide environments does not cause yawning.
The short answer is that yawning is normal. It is common and usually is totally benign. However, if there is an increase in yawning that cannot be explained by lack of sleep or some of the other causes mentioned above, then yawning can be a symptom of some disease. The most common medical problems that are associated with increased yawning are sleep deprivation, insomnia, sleep apnea, narcolepsy, and many medicines that cause sleepiness.
There are some other medical diseases that cause yawning including bleeding around the heart, brain tumor, multiple sclerosis, stroke, and even heart attack. In most people yawning is a normal reflex, although poorly understood. However, if you experience excessive yawning for no apparent reason, it is wise to visit your physician and make sure there is nothing going on that is abnormal. The Bottom Line In most people yawning is a normal reflex, although poorly understood.
Another hypothesis is that we yawn because we are tired or bored. But this, too, is probably not the case because the PVN also plays a role in penile erection, which is not typically an event associated with boredom.
It does appear that the PVN of the hypothalamus is, among other things, the "yawning center" of the brain. It contains a number of chemical messengers that can induce yawns, including dopamine, glycine, oxytocin and adrenocorticotropic hormone ACTH.
ACTH, for one, surges at night and prior to awakening, and induces yawning and stretching behavior in humans. The process of yawning also appears to require production of nitric oxide by specific neurons in the PVN.
Yawning likewise appears to have a feedback component: if you stifle or prevent a yawn, the process is somewhat unsatisfying. The stretching of jaw and face muscles seems to be necessary for a yawn to be satisfying. More information is needed to fully understand the origin and meaning of the yawn.
It may be that other parts of the brain are involved. Interestingly, although yawning is a normal function, why it occurs excessively in some patients with brain damage or with multiple sclerosis is unclear. Answer originally published on August 12, Sign up for our email newsletter. Already a subscriber? It is controlled by a brain region called the hypothalamus, and involves production of adrenaline and cortisol, hormones that increase alertness and help us deal with stress.
That might also explain why people often yawn when feeling anxious — as do monkeys. Explaining contagious yawning is even trickier.
Apart from humans, the only other species known to catch yawns from one another are chimps, dogs which can be infected by human yawns , the wonderfully named high-yawning Sprague-Dawley rat, budgerigars and lions, who appear to use yawning to send signals to the rest of the pride.
These animals are all very sociable, which suggests contagious yawning might have something to do with empathy, or at least a tendency to mimic and synchronise actions with others, a foundation of empathy. But whether contagious yawning helps us build social relationships is another matter.
It could simply be a by-product of the way we and other highly-social animals instinctively respond to others. What is yawning?
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