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 Blood composition depends on: 1. Diet 2. Cellular metabolism 3. Urine output  How the kidneys manage blood composition: 1. Excretion of nitrogenous wastes 2. Water/electrolyte balance of the blood 3. Ensuring proper blood pH © 2015 Pearson Education, Inc.

 The main fluid compartments that water occupies: 1. Intracellular Fluid (ICF) : fluid inside cells 2. Extracellular Fluid (ICF) : fluid outside cells 1. interstitial fluid 2. blood plasma, CSF, lymph, humors of the eye  Changes in electrolyte balance can influence blood volume/blood pressure, cellular activity © 2015 Pearson Education, Inc.

Lungs Gastrointestinal tract Kidneys Blood plasma Interstitial fluid Intracellular fluid in tissue cells O2O2 CO 2 Nutrients O2O2 CO 2 Nutrients H 2 O, Ions H2OH2O Ions Nitrogenous wastes

 Electrolytes: charged particles (ions) that conduct an electrical current in aqueous solution  allow reactions that require electrical charge to take place  Cell membrane stability  Muscle contraction  Nerve impulse  Body electrolytes include:  Sodium (Na ⁺)  Potassium (K ⁺)  Calcium (Ca ⁺⁺)  Magnesium (Mg ⁺⁺) © 2015 Pearson Education, Inc.

 Osmoreceptors: cells in the hypothalamus  Activated by small changes in blood composition  Results in a dry mouth  Reinforces the drive to drink water  What is a diuretic? A substance that causes your kidneys to eliminate more salt and water than it should © 2015 Pearson Education, Inc.

 Hormones regulate reabsorption of water and electrolytes by the kidneys  Antidiuretic hormone (ADH)  Hypothalamus tells posterior pituitary to release ADH  prevents excessive water loss in the urine  increases water reabsorption  Aldosterone (produced by adrenal cortex)  increases sodium and water reabsorption;  decreases potassium reabsorption © 2015 Pearson Education, Inc.

 Regulates blood pressure  The juxtaglomerular (JG) apparatus of the renal tubules sense drop in BP or solute concentration  Causes release of the enzyme renin into blood  Renin produces angiotensin II  Acts directly on the blood vessels to vasoconstrict  Works to reduce filtrate volume © 2015 Pearson Education, Inc.

 Ideal blood pH: between 7.35 and 7.45  Kidneys : biggest impact in controlling pH  Other acid-base controlling systems  Blood buffers  Respiration © 2015 Pearson Education, Inc.

HCl H 2 CO 3 HCO 3 − H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Cl − (a) A strong acid such as HCl dissociates completely into its ions. (b) A weak acid such as H 2 CO 3 does not dissociate completely.

 The bicarbonate buffer system is a mixture of:  sodium bicarbonate (NaHCO 3 )  carbonic acid (H 2 CO 3 ) © 2015 Pearson Education, Inc.

 Bicarbonate ions (HCO 3 – ):  react with strong acids to change them to weak acids HCl + NaHCO 3  H 2 CO 3 + NaCl strong acid weak base weak acid salt  Carbonic acid :dissociates in the presence of a strong base to form a weak base and water NaOH + H 2 CO 3  NaHCO 3 + H 2 O strong base weak acidweak base water © 2015 Pearson Education, Inc.

 As blood pH changes:  respiratory rate can rise and fall to:  retain CO 2 (decreasing the blood pH)  remove CO 2 (increasing the blood pH) CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 − © 2015 Pearson Education, Inc.

 When blood pH rises:  Bicarbonate ions are excreted  Hydrogen ions are retained by kidney tubules  When blood pH falls:  Bicarbonate ions are reabsorbed  Hydrogen ions are secreted © 2015 Pearson Education, Inc.