vasovagal syncope during blood draw. #vasovagalsyncope #vasovagal #parasympatheticactivation #passingout #syncope | Mary Johnson

Have You Ever Fainted? Here's WhyVasovagal syncope is a common physiological response to emotional stress or physical triggers like the sight of blood. This is a protective overreaction of the vagus nerve. When this nerve over-stimulates, it causes a rapid drop in heart rate and blood pressure, leading to a temporary loss of consciousness. You can counteract this by using isometric muscle contractions to force blood flow back to the cranial vault. Understanding the autonomic nervous system allow