Concentration of urine is controlled by the hormone ADH (anti-diuretic hormone)This hormone is released into the bloodstream; by the posterior pituitary glandIf the water concentration in the blood is too high (dilute); this is detected by the receptors in the brainThe co-ordination centre in the brain receives information and co-ordinates a responsePituitary gland releases less ADH, so less water is now reabsorbed from the kidney tubulesThis an example of negative feedback