Stimuli are signals that trigger the senses. Receptors detect the stimuli and neurons send the signals to the brain where they're interpreted. Each sense organ includes receptors that capture relevant stimuli for transmission to the brain. The receptors in the skin are mechanoreceptors and thermoreceptors.
AWWA Butterfly valves are quick opening valves that consist of a metal circular disc or vane with its pivot axes at right angles to the direction of flow in the pipe, which when rotated on a shaft, seals against seats in the valve body. They are normally used as throttling valves to control flow.
There are also two semilunar valves; one between the right ventricle and the lungs (pulmonary semilunar valve) and one between the left ventricle and the aorta (aortic semilunar valve). The main purpose of the valves is to prevent backflow of blood in the heart. There are things called the chordae tendinae and papillary muscle that help control the opening and closing of the valves as blood flows through them. There are also valves in the veins.