Final answer:
Antidiuretic hormone (ADH) is released by the pituitary when water intake is low. ADH signals the kidneys to reabsorb more water, preventing further fluid loss in the urine and increasing overall fluid levels in the body.
Step-by-step explanation:
When water intake is low, spinal cells signal the pituitary to release antidiuretic hormone (ADH). ADH is secreted by the cells in the hypothalamus and stored in the posterior pituitary until released upon nervous stimulation. The primary role of ADH is to signal the kidneys to reabsorb more water, preventing the loss of additional fluid in the urine and increasing overall fluid levels in the body. ADH also constricts peripheral vessels.
When water intake is low, spinal cells in the brain, specifically in the hypothalamus, signal the pituitary gland to release the antidiuretic hormone (ADH), also known as vasopressin. ADH helps to prevent water loss by signaling the kidneys to reabsorb more water from the filtrate, which results in less water being lost in urine and helps maintain blood volume and pressure. As a result, urine becomes more concentrated, appearing darker. This essential hormone is also involved in vasoconstriction, which can help to increase blood pressure during episodes of hemorrhaging. It is important to note that ADH is not related to the 'fight or flight' response, which is associated with epinephrine.