Dictionary

vasodilator An agent that acts as a blood vessel dilator, opening blood vessels by relaxing their muscular walls. For example, nitroglycerin is a vasodilator, as are the angiotensin converting enzyme (ACE) inhibitors.

vasomotor Relating to the nerves and muscles that cause blood vessels to constrict or dilate.

vasomotor rhinitis Inflammation of the nose (rhinitis) due to abnormal nerve control of the blood vessels in the nose. Vasomotor rhinitis is not allergic rhinitis. Decongestant medications are used to temporarily reduce swelling of sinus and nasal tissues leading to an improvement of breathing and a decrease in obstruction.

vasopressin See antidiuretic hormone.

vasovagal attack See vasovagal reaction.

vasovagal reaction A reflex of the involuntary nervous system that causes the heart to slow down and, at the same time, affects the nerves to the blood vessels in the legs, permitting those vessels to dilate (widen). As a result, the heart puts out less blood, the blood pressure drops, and the blood that is…

vasovagal syncope The temporary loss of consciousness in a particular kind of situation (situational syncope, or fainting) due to a vasovagal reaction. See also syncope.

VBAC Vaginal birth after caesarean section. See caesarean section, vaginal birth after.

VDRL test Venereal Disease Research Laboratory test, a blood test for syphilis. A negative (nonreactive) VDRL test is compatible with a person not having syphilis. However, a person may have a negative VDRL and still have syphilis because in the early stages of the disease, the VDRL often gives false negative results. The VDRL test…

vector In medicine, a carrier of disease or of medication. For example, in malaria a mosquito is the vector that carries and transfers the infectious agent. In molecular biology, a vector may be a virus or a plasmid that carries a piece of foreign DNA to a host cell.

VEG-F Vascular endothelial growth factor.

vein A blood vessel that carries blood that is low in oxygen content from the body back to the heart. The deoxygenated form of hemoglobin (deoxyhemoglobin) in venous blood makes it appear dark. Veins are part of the afferent wing of the circulatory system, which returns blood to the heart. In contrast, an artery is…