Webster's New World Medical Dictionary

syncope, coughing
The temporary loss of con-
sciousness upon coughing. See also 
syncope; syn-
cope, situational; vasovagal reaction.
syncope, defecation
The temporary loss of con-
sciousness upon defecating (having a bowel move-
ment). See also 
syncope; syncope, situational;
vasovagal reaction.
syncope, micturition
The temporary loss of
consciousness upon urinating (micturation). See
also 
syncope; syncope, situational; vasovagal
reaction.
syncope, situational
The temporary loss of con-
sciousness in a particular kind of situation. The sit-
uations that trigger this reaction are diverse and
include having blood drawn, straining while urinat-
ing 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 syn-
drome. See also 
syncope; vasovagal reaction.
syncope, swallowing
The temporary loss of
consciousness upon swallowing. See also 
syncope;
syncope, situational; vasovagal reaction.
syncope, vasodepressor
See 
syncope,
situational.