Pav·lov \ˈpäv-ˌlȯf, ˈpav-, -ˌlȯv\ , Ivan Petrovich (1849–1936), Russian physiologist. Pavlov is most famous for developing the concept of the conditioned reflex. In his classic experiment he trained a hungry dog to salivate at the sound of a bell by conditioning the dog to associate the sound of the bell with the sight of food. His earlier research had been concerned with cardiac physiology and the regulation of blood pressure. Carefully dissecting the fine cardiac nerves, he demonstrated that the strength of the heartbeat was controlled by nerves leaving the cardiac plexus. He later turned his attention to the study of the secretory activity of digestion. Having devised with the German physiologist Rudolph Heidenhain an operation to prepare what is now often called a Pavlov pouch, he was able to isolate the stomach from salivary and pancreatic secretions and thereby study the gastrointestinal secretions in a normal animal over its life span. This research led him to formulate the laws of the conditioned reflex. In 1904 he was awarded the Nobel Prize for Physiology or Medicine for his research on the physiology of digestive secretions.