Fainting, “blacking out,” or syncope is the temporary loss of consciousness followed by the return to full wakefulness. This loss of consciousness may be accompanied by loss of muscle tone that can result in falling or slumping over. People faint for many reasons, including: abnormal heart rhythms, standing too fast, exhaustion, emotional upset and/or stress, overheating, illness or some medications. Some causes of fainting are not easy to explain, and some causes of unexplained fainting can be life-threatening.
Vasovagal syncope (also called “neurocardiogenic syncope”) is a common cause of fainting. The vagus nerve is overstimulated and causes the body’s blood vessels to dilate and the heart to slow down. This anti-adrenaline effect decreases the ability of the heart to pump blood upward to the brain against gravity. Without blood flow, the brain turns off.