A forceful expulsion of breath, often accompanied by saliva and mucus, is released through the mouth and nose during a sneeze. The involuntary process of sneezing is an essential component of an individual'sÂ immune system. A single sneeze is said toÂ release around 100,000 harmful microbes into the air.
The onset of a sneeze occurs along the nerve endings found on the nose. The nostrils and sinuses are covered with tiny, hair-like projections called cilia, which detect nasal inhalation of foreign particles. When the nose becomes irritated, a tickling sensation is felt and the brain's "sneeze center" is activated. A stimulus sends a signal to this particular region in the lower brain stem to immediately block access to the throat, mouth and eyes. This results in a violent contraction of the chest muscles and the intense build up of pressure in the lungs. Once the stress exceeds the capacity for holding the breath in, the throat muscles expand and a gust of air is ejected from the oral and nasal orifices.
Contrary to popular belief, a sneeze does not trigger the heart to suddenly stop. During a sneeze, the blood flow is altered, which in turn affects the rhythmic pattern of the heart. A lengthy delay in the next heartbeat causes that beat to be more pronounced. The myth probably stemmed from the feeling of having the heart skip a beat due to the delay, according to Dr. Richard Conti of the American College of Cardiology.