In addition to this, most of the things we do have a purpose. Upon laughing, the brain pressures us to do two simultaneous things. One is visual, consisting of specific facial gestures. The second is phonic, with the production of certain sounds. During exuberant laughter, there is a change in many parts of the body including the arm, leg and trunk muscles.
Laughter helps release emotion and tension.
People often store emotions rather than express them if something angers, frightens, saddens, stresses, or bores them. Laughter is another way for these emotions to find a way out harmlessly. Currents of varying intensity produce a wide range of facial responses. The epiglottis half-closing upsets the respiratory system, so that air intake occurs in irregular gasps, rather than calm breathing. Under extreme circumstances, the tear ducts are activated, so that while the mouth is opening and closing and there is a struggle for a sufficient amount of oxygen intake, the face becomes moist and often red.