syncope, situational

syncope, situational The temporary loss of consciousness in a particular kind of situation. The situations that trigger this reaction are diverse and include having blood drawn, straining while urinating or defecating, and coughing. The reaction can be caused also by emotional stress, fear, or pain. When experiencing the trigger condition, the person often becomes pale and feels nauseated, sweaty, and weak just before losing consciousness. Situational syncope is caused by a reflex of the involuntary nervous system called the vasovagal reaction that causes the heart to slow down (bradycardia) while at the same time leading the nerves that serve the blood vessels in the legs to permit those vessels to dilate (widen). The result is that the heart puts out less blood, blood pressure drops, and circulating blood tends to go into the legs rather than to the head. The brain is deprived of oxygen, and the fainting episode occurs. Also known as vasovagal syncope, vasodepressor syncope, and Gower syndrome. See also syncope; vasovagal reaction.