Editing Exhalation (section)

===Voluntary expiration===

The neurological pathway of voluntary exhalation is complex and not fully understood. However, a few basics are known. The [[motor cortex]] within the cerebral cortex of the brain is known to control voluntary respiration because the motor cortex controls voluntary muscle movement.<ref name="Article #1">{{cite journal |doi=10.1152/japplphysiol.00641.2002 |pmid=12754178 |title=Neural correlates of voluntary breathing in humans |journal=Journal of Applied Physiology |volume=95 |issue=3 |pages=1170–8 |year=2003 |last1=McKay |first1=L. C. |last2=Evans |first2=K. C. |last3=Frackowiak |first3=R. S. J. |last4=Corfield |first4=D. R. |s2cid=15122094 }}</ref> This is referred to as the corticospinal pathway or ascending respiratory pathway.<ref name="Article #1" /><ref name="Article #3">{{cite journal |doi=10.1378/chest.117.1.205 |pmid=10631221 |title=The Control of Breathing in Clinical Practice |journal=Chest |volume=117 |issue=1 |pages=205–225 |year=2000 |last1=Caruana-Montaldo |first1=Brendan |citeseerx=10.1.1.491.4605 }}</ref> The pathway of the electrical signal starts in the motor cortex, goes to the spinal cord, and then to the respiratory muscles. The spinal neurons connect directly to the respiratory muscles. Initiation of voluntary contraction and relaxation of the internal and external internal costals has been shown to take place in the superior portion of the primary motor cortex.<ref name="Article #1" /> Posterior to the location of thoracic control (within the superior portion of the primary motor cortex) is the center for diaphragm control.<ref name="Article #1" /> Studies indicate that there are numerous other sites within the brain that may be associated with voluntary expiration. The inferior portion of the [[primary motor cortex]] may be involved, specifically, in controlled exhalation.<ref name="Article #1" /> Activity has also been seen within the supplementary motor area and the premotor cortex during voluntary respiration. This is most likely due to the focus and mental preparation of the voluntary muscular movement.<ref name="Article #1" />

Voluntary expiration is essential for many types of activities. Phonic respiration (speech generation) is a type of controlled expiration that is used every day. Speech generation is completely dependent on expiration, this can be seen by trying to talk while inhaling.<ref name="Article #6">{{cite web|last=Newman|first=D|title=The Physiology of Speech Production|url=http://www.dur.ac.uk/daniel.newman/phon6.pdf|access-date=31 March 2012}}</ref>  Using airflow from the lungs, one can control the duration, amplitude, and pitch.<ref name="Article #5">{{cite journal |last1=Heman-Ackah |first1=Yolanda D. |year=2005 |title=Physiology of voice production: considerations for the vocal performer |journal=Journal of Singing |volume=62 |issue=2 |pages=173–6}}</ref> While the air is expelled it flows through the glottis causing vibrations, which produces sound.  Depending on the glottis movement the pitch of the voice changes and the intensity of the air through the glottis change the volume of the sound produced by the glottis.{{citation needed|date=May 2015}}