water is the main constituent of our body accounting for about 60 percent of our body weight and is vital for life to keep ourselves functioning normally it's important that the water content of our blood is controlled if the concentration of water in our blood is too high then water will move into the body cells by osmosis too much moves into the cells then the cells May burst conversely if the concentration of water in our blood is too low then water will move out of the cells into the blood this causes the cells to shrink our kidneys work with our brain to help regulate our bodily water content by controlling how much water and salts are reabsorbed and how much is lost as urine the amount of water reabsorbed in our kidney nephrons is controlled by antidiuretic hormone or ADH ADH makes the collecting ducts of the nephrons more permeable so that more water is reabsorbed into the blood the brain monitors the water content of the blood and instructs the pituitary gland to secrete ADH into the blood according to how much is needed following things can change the concentration of the blood drinking lots of water which increases blood water content sweating a lot reduces blood water content and eating salty foods this also reduces blood water content the whole process of water regulation is an example of a negative feedback system let's take a closer look at that if the water content of the blood decreases a receptor in our brain detects that the water content is too low the coordination Center in the brain receives the information and organizes a response the pituitary gland releases ADH so more water is reabsorbed from the kidneys and more concentrated urine is produced and the blood water content then returns to normal put a content of the blood increases the opposite occurs our brain detects that the water content is too high and directs the pituitary gland to release less ADH so less water is reabsorbed from our kidneys and more dilute urine is produced and once again the blood water content returns to normal many medicines and illnesses can affect how our body controls its water content therefore it's important that pharmacists like Sarah and other healthcare workers know how our body regulates this process in order to support patients to manage their illnesses and safely take their medicines foreign [Laughter] [Music]