Sneeze
A REFLEX that forcefully expels air through the NOSE. A sneeze originates with an irritation to the mucous membranes in the nose, sometimes perceptible as a tickling sensation and other times not noticeable, that activates NERVE impulses. The fifth cranial nerve (trigeminal nerve) carries the impulse to a cluster of specialized neurons (nerve cells) in the brainstem (the part of the BRAIN that regulates the body’s basic vital functions including reflexes). Scientists call this area the sneeze center, though they do not know its precise location because it is not physically distinct from other portions of the brainstem. The sneeze center sends nerve signals back to the body through numerous nerve pathways that activate a coordinated response.
A sneeze results when the brainstem signals the VOCAL CORDS to close, allowing air pressure to build in the airway, then signals the DIAPHRAGM and various muscles in the chest, THROAT, and face to contract and the vocal cords to open. This sequence of events expels air through the nose with great force; researchers have measured sneezes leaving the nose at the equivalent of 100 miles per hour. The pressure blows mucus and irritants from the nose.
When the irritation stops, the cycle of the sneeze reflex ends. People who have a health condition such as SINUSITIS or ALLERGIC RHINITIS may sneeze so often that their noses become raw and irritated. Nasal sprays containing decongestants help reduce swelling of the nasal passages; those containing antihistamines help subdue the nose’s local reaction to allergens. These approaches are often effective in reducing sneezing episodes. Increasing the moisture content of the nasal mucosa, such as by BREATHING humidified air and drinking plenty of fluids, helps relieve irritation.
Many viruses, such as those that cause COLDS and INFLUENZA, have adapted their structures to take advantage of the sneeze mechanism, using it to disperse themselves to new hosts. To reduce the spread of these infections, health experts recommend sneezing into disposable tissues and discarding them, then washing the hands thoroughly with soap and water.
Some people sneeze when they step into sunlight or look up at a sunlit sky, called photic sneezing. Doctors do not know why photic sneezing occurs, though it is an inherited trait. Some researchers speculate that sunlight (or any very bright light) stimulates brain activity near the brain’s sneeze center, which sends the message to the body to sneeze. About one in four people experiences photic sneezing.
A sneeze results when the brainstem signals the VOCAL CORDS to close, allowing air pressure to build in the airway, then signals the DIAPHRAGM and various muscles in the chest, THROAT, and face to contract and the vocal cords to open. This sequence of events expels air through the nose with great force; researchers have measured sneezes leaving the nose at the equivalent of 100 miles per hour. The pressure blows mucus and irritants from the nose.
When the irritation stops, the cycle of the sneeze reflex ends. People who have a health condition such as SINUSITIS or ALLERGIC RHINITIS may sneeze so often that their noses become raw and irritated. Nasal sprays containing decongestants help reduce swelling of the nasal passages; those containing antihistamines help subdue the nose’s local reaction to allergens. These approaches are often effective in reducing sneezing episodes. Increasing the moisture content of the nasal mucosa, such as by BREATHING humidified air and drinking plenty of fluids, helps relieve irritation.
Many viruses, such as those that cause COLDS and INFLUENZA, have adapted their structures to take advantage of the sneeze mechanism, using it to disperse themselves to new hosts. To reduce the spread of these infections, health experts recommend sneezing into disposable tissues and discarding them, then washing the hands thoroughly with soap and water.
Some people sneeze when they step into sunlight or look up at a sunlit sky, called photic sneezing. Doctors do not know why photic sneezing occurs, though it is an inherited trait. Some researchers speculate that sunlight (or any very bright light) stimulates brain activity near the brain’s sneeze center, which sends the message to the body to sneeze. About one in four people experiences photic sneezing.
Posted in Health and Wellness
