A vagal response, or a vasovagal response, occurs when the heart rhythm slows and the heart rate and blood pressure drop quickly, reducing blood flow to the brain, according to the National Center for Biotechnology Information. As a result, the individual faints or briefly becomes unconscious, states Mayo Clinic.
A vasovagal response, also called vasovagal syncope, is usually harmless, notes Mayo Clinic. It is the body's overreaction to an event, such as seeing a person bleeding, or during times of severe emotional distress. A vasovagal response is not necessarily abnormal. All healthy people have the nerve pathways related to the response, but susceptibility levels differ from person to person, according to the National Center for Biotechnology Information.