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Effect of temporary impairment of blood circulation to a part of the body. It is often used as a synonym for fainting, which is loss of consciousness due to inadequate blood flow to the brain. Paleness, nausea, sweating, and then pupil dilation, yawning, deep rapid breathing, and rapid heartbeat usually precede it. It lasts from under a minute to several minutes and may be followed by headache, confusion, and a weak feeling. The cause may be physical (e.g., heart failure, low blood sugar) or emotional (e.g., fear, anxiety). Abnormal vagus or autonomic nerve response can cause fainting (without preceding symptoms) triggered by ordinary activities such as urination, swallowing, coughing, or standing up or by pressure on the pulse point in the neck. Local syncope is coldness and numbness in a small area, especially the fingers, from diminished blood flow.
This entry comes from Encyclopædia Britannica Concise. For the full entry on syncope, visit Britannica.com.