Water Regulation - Biology Notes PDF

Regulation of water Average person expels 1.5 L urine/day (lowest 0.4, highest 25) Movement of water If VERY dehydrate...

Regulation of water Average person expels 1.5 L urine/day (lowest 0.4, highest 25) Movement of water If VERY dehydrated, some urine will be produces (excretion of requires excess solutes and waste) 1. Aquaporin minimal urine production called “obligatory urine loss” channels ANTIDIURETIC HORMONE 2. A gradient of changes how much water is reabsorbed by nephrons solutes to move Diuretic -> word diuresis (produce more urine) by osmosis ADH causes anti-diuresis (less urine) ADH signals nephrons to reabsorb more water in kidneys ADH has a role in affecting diameter of blood vessel DIURETICS Another name for ADH = Vasopressin alcohol compounds release of ADH NEUROENDOCRINE CELLS Diabetes insipidus Neurons that release neurotransmitters instead of hormones are rare disease called ‘neuroendocrine cells’ Produces large volumes of urine became nephron tubules don’t reabsorb enough water These type of cells produce ADH located in hypothalamus Axons project into posterior pituitary (pituitary gland) DIABETES INSIPIDUS If the total body water decreases, then the Neurogenic (central) diabetes insipidus extracellular fluid (ECF) volume decreases caused by damage (head trauma, or surgery to hypothalamus or posterior which causes a decrease in blood pressure. * He pituitary gland) If the total body water decreases, then the ratio ADH not released normally of items dissolved in the blood and water will increase (same amount of solutes but dissolved in less plasma volume). The osmolarity of blood Nephrogenic diabetes insipidus will increase. Rare genetic mutations ADH can’t respond to the hormone when it’s in the blood Barorecpetors sensory receptors located in aortic arch and in carotid sinus “normal” BP, receptors send AP to cardiovascular centre in medulla oblongata BP decrease = less AP BP increase = more AP Osmoreceptors sensory receptor in hypothalamus plasma osmolarity increase = more AP, more ADH plasma osmolarity decrease = less AP Plasma osmolarity high, water rushes out of osmoreceptor and shrivels, AP generated, excited neurotransmitter released onto neuroendocrine cells, which generates AP, ADH stored in vesicles and axon terminals, ADH released and enters blood vessels nearby Receptors for ADH found on plasma membrane of some cells of the body, including principle cells of collecting duct Principle cells contain Aquaporin ll channels in the vesicles Once ADH enters cells, stimulates movement of vesicles, move to the luminal/apical membrane Allows for more movement of water into collecting ducts