Why Do We Yawn? The definition of yawning is to open the mouth involuntarily with a prolonged, deep inhalation of air. Yawning is a normal response to fatigue and drowsiness, but excessive yawning can be caused by a vasovagal reaction and may indicate a heart problem. Normal yawning may be induced to cleanse the brain. At the deepest part of the breath when the lungs have the greatest force, the lungs fill up the ribcage, …showed first 75 words of 531 total…

…showed last 75 words of 531 total…have the capacity to hold about one fourth of that, so our cerebrospinal fluid is replaced several times per day during normal circulation. The flow of the CSF has much to do with the intercranial pressure, which is different from the blood pressure of the body. When yawning puts pressure on the brain, the CSF is forced through its absorption pathways at an accelerated rate taking brain waste products with it. Yawning cleans the brain.