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THE CONTROL OF WATER BALANCE © 2016 Paul Billiet ODWS Osmoregulation A combination of three factors: Concentration The concentration of the solutes dissolved in the boy fluid will influence osmosis Volume The volume of the body fluids will influence the pressure they exert Composition The different types of dissolved solutes will influence body function. © 2016 Paul Billiet ODWS Conformers and Regulators Conformers change with their environment Their tissues must tolerate changes in solute concentration © 2016 Paul Billiet ODWS Conformers and Regulators Regulators resist changes in the environment They possess homeostatic mechanisms to control their internal concentration © 2016 Paul Billiet ODWS Estuarine invertebrates In estuaries the salt levels are always changing Fresh water Shore crab (Carcinus maenas) © 2016 Paul Billiet ODWS © P Billiet Seawater Estuarine invertebrates Upogebia pugettensis Neotrypaea californiensis © 2016 Paul Billiet ODWS Mud Crab (Rhithropanopeus harrisii) © 2016 Paul Billiet ODWS © 2016 Paul Billiet ODWS Fluid compartments and exchange surfaces EXTERNAL ENVIRONMENT Exchange surfaces Lungs Intestines Skin Kidneys Capillary networks BLOOD PLASMA (3dm3) TISSUE FLUID (11dm3) CYTOPLASM (28dm3) Plasma membranes NB volumes for a 70kg male © 2016 Paul Billiet ODWS BODY FLUID BALANCE INPUT ......……....… AND …......…….. OUTPUT Drinking COLON BODY LUNGS Breath SKIN Sweat KIDNEYS Urine • A mammal cannot stop breathing because it would suffocate • A mammal cannot stop sweating because it would over heat • It can reduce water loss by the kidneys • It can add water to the body by drinking © 2016 Paul Billiet ODWS Dehydration NEGATIVE FEEDBACK Dehydration Blood concentration rises © 2016 Paul Billiet ODWS Thirst reflex Hypothalamus Kidney Osmoreceptors ADH Concentration of circulating blood Drinking, water absorbed by the colon Less urine + concentrated urine Blood concentration falls Hyperhydration NEGATIVE FEEDBACK Concentration of circulating blood Drinking Blood concentration falls Hypothalamus Osmoreceptors Kidney More urine + diluted urine Blood concentration rises Note: for a terrestrial animal this is a less likely situation and it is easy to lose water Dehydration is more likely so the control system has evolved to saving or getting water © 2016 Paul Billiet ODWS
