Question

How do multiple organ systems work together to restore balance from dehydration?

Answer 1

Body fluids are mainly water and electrolytes, and the three main organs that regulate fluid balance are the brain, the adrenal glands and the kidneys.

In the body, several mechanisms work together to maintain water balance. These include

• Thirst

• Interaction of the pituitary gland and kidneys

• Osmosis

Thirst is one of the most important mechanisms to maintain water balance. When the body needs water, nerve centers deep within the brain are stimulated, resulting in the sensation of thirst. The sensation becomes stronger as the body’s need for water increases, motivating a person to drink the needed fluids. When the body has excess water, thirst is suppressed.

An interaction between the pituitary gland and the kidneys provides another mechanism. When the body is low in water, the pituitary gland (located at the base of the brain) secretes vasopressin (also called antidiuretic hormone) into the bloodstream. Vasopressin stimulates the kidneys to conserve water and excrete less urine. When the body has excess water, the pituitary gland secretes little vasopressin, enabling the kidneys to excrete excess water in the urine.

In osmosis, water flows passively from one area or compartment of the body to another. This passive flow allows the larger volumes of fluid in the cells and the area around the cells to act as reservoirs to protect the more critical but smaller volume of fluid in the blood vessels from dehydration.

Mineral salts (electrolytes), such as sodium and potassium, are dissolved in the water in the body. Water balance and electrolyte balance are closely linked. The body works to keep the total amount of water and the levels of electrolytes in the blood constant. For example, when the sodium level becomes too high, thirst develops, leading to an increased intake of fluids. In addition, vasopressin (also called antidiuretic hormone), a hormone secreted by the brain in response to dehydration, causes the kidneys to excrete less water. The combined effect is an increased amount of water in the blood. As a result, sodium is diluted and the balance of sodium and water is restored. When the sodium level becomes too low, the kidneys excrete more water, which decreases the amount of water in the blood, again restoring the balance.