Editing Exhalation (section)

====Yawning====

[[Yawning]] is considered a non-respiratory gas movement.  A non-respiratory gas movement is another process that moves air in and out of the lungs that do not include breathing. Yawning is a reflex that tends to disrupt the normal breathing rhythm and is believed to be contagious as well.<ref name="yawning primary">{{cite journal |doi=10.1080/09515080802513292 |title=Content and Contagion in Yawning |journal=Philosophical Psychology |volume=21 |issue=6 |pages=721–37 |year=2008 |last1=Sarnecki |first1=John |s2cid=144972289 }}</ref>  The reason why we yawn is unknown. A common belief is that yawns are a way to regulate the body's levels of O<sub>2</sub> and CO<sub>2,</sub> but studies done in a controlled environment with different levels of O<sub>2</sub> and CO<sub>2</sub> have disproved that hypothesis.  Although there is not a concrete explanation as to why we yawn, others think people exhale as a cooling mechanism for our brains.  Studies on animals have supported this idea and it is possible humans could be linked to it as well.<ref name=Yawning>{{cite journal |doi=10.3389/fnevo.2011.00007 |pmid=22319494 |title=Changes in Physiology before, during, and after Yawning |journal=Frontiers in Evolutionary Neuroscience |volume=3 |pages=7 |year=2012 |last1=Corey |first1=Timothy P. |last2=Shoup-Knox |first2=Melanie L. |last3=Gordis |first3=Elana B. |last4=Gallup |first4=Gordon G. |pmc=3251816 |doi-access=free }}</ref> What is known is that yawning does ventilate all the alveoli in the lungs.{{citation needed|date=June 2022}}