In this case, the damper is normally opened by the force of the spring but can be closed by the force of the motor. Removal of electrical power re-opens the damper. This style of damper is advantageous because it is fail safe; if the control to the damper fails, the damper opens and allows air to flow.
The adrenal glands, located on the top of each kidney, are responsible for releasing different hormones. Adrenal gland disorders occur when the adrenal glands produce too much or too little of these hormones.
The outer part, the adrenal cortex, produces several classes of steroid hormones such as estrogen, progesterone, cortisol, aldosterone and some others. The inner part, called the adrenal medulla, secretes chemicals like epinephrine, norepinephrine and dopamine. These two parts of the adrenal glands are functionally very different, and have different embryological origins. In some species of fish and amphibians these functions are carried out by two different organs.