Water balance in mammals Water balance in mammals is controlled by the kidneys, hypothalamus and the adrenal glands It involves 3 main hormones: Anti-diuretic hormone (ADH) also called vasopressin produced by hypothalamus Anti-diuretic hormone (ADH) also called vasopressin produced by hypothalamus Renin produced by kidneys Renin produced by kidneys Aldosterone produced by the adrenals Aldosterone produced by the adrenals Water balance is also called osmoregulation

Water In Water Out Metabolic water Water from food Free water Drinking Faeces Urine Evaporation from skin Exhaled air

Water Increase

Normal concentration of solutes Blood volume decreases - blood pressure falls Blood volume increases blood pressure increases Increased renin- stimulates aldosterone - active absorption of sodium Decreases renin - decreases aldosterone -decreases active absorption of sodium

Response: Response: Salt concentration in blood decreases and increased blood volume Increased water intake Effectors: Effectors: kidneys (Increased water and salt reabsorption - less urination) Stimulates pituitary gland Receptor: Receptor: osmoreceptors, hyptothalamus Adrenals produce aldosterone Stimulus: Stimulus: Blood Pressure Drops Receptor: Receptor: Glomerulus, kidneys Produce Renin Low fluid intake or high water loss Increases thirst Produces ADH Stimulus: Stimulus: High salt concentration