1. a sudden disturbance of mental equilibrium. It is marked by hypotension and coldness of the skin, and often by tachycardia and anxiety.
Untreated shock can be fatal.
The diameter of the blood vessels is controlled by impulses from the nervous system which cause the muscular walls to contract. The nervous system also affects the rapidity and strength of the heartbeat, and thereby the blood pressure as well. Shock, which is associated with a dangerously low blood pressure, can be produced by factors that attack the strength of the heart as a pump, decrease the volume of the blood in the system, or permit the blood vessels to increase in diameter. There are five main types of circulatory shock. Low-volume shock occurs whenever there is insufficient blood to fill the circulatory system.