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27-1 Water, Electrolytes, and Acid-Base Balance. 27-2 Body Fluids Intracellular –All fluids inside cells of body –About 40% of total body weight Extracellular.

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Presentation on theme: "27-1 Water, Electrolytes, and Acid-Base Balance. 27-2 Body Fluids Intracellular –All fluids inside cells of body –About 40% of total body weight Extracellular."— Presentation transcript:

1 27-1 Water, Electrolytes, and Acid-Base Balance

2 27-2 Body Fluids Intracellular –All fluids inside cells of body –About 40% of total body weight Extracellular –All fluids outside cells –About 20% of total body weight –Subcompartments Interstitial fluid and plasma; lymph, CSF, synovial fluid

3 27-3 Body Fluid Compartments

4 27-4 Water Content Regulation Content regulated so total volume of water in body remains constant Kidneys primary regulator of water excretion Regulation processes –Osmosis –Osmolality –Baroreceptors –Learned behavior Sources of water –Ingestion –Cellular metabolism Routes of water loss –Urine –Evaporation Perspiration Respiratory passages –Feces

5 27-5 Extracellular Fluid Osmolality Osmolality –Adding or removing water from a solution changes this Increased osmolality –Triggers thirst and ADH secretion Decreased osmolality –Inhibits thirst and ADH secretion

6 27-6 Hormonal Regulation of Blood Osmolality

7 27-7 Regulation of ECF Volume Mechanisms –Neural –Renin-angiotensin- aldosterone –Atrial natriuretic hormone (ANH) –Antidiuretic hormone (ADH) Increased ECF results in –Decreased aldosterone secretion –Increased ANH secretion –Decreased ADH secretion –Decreased sympathetic stimulation Decreased ECF results in –Increased aldosterone secretion –Decreased ANH secretion –Increased ADH secretion –Increased sympathetic stimulation

8 27-8 Hormonal Regulation of Blood Volume

9 27-9 Hormonal Regulation of Blood Volume

10 27-10 Regulation of ECF Volume

11 27-11 Regulation of ICF and ECF

12 27-12 Regulation of Electrolytes in ECF Electrolytes –Molecules or ions with an electrical charge Water ingestion adds electrolytes to body Kidneys, liver, skin, lungs remove from body –Concentration changes only when growing, gaining or losing weight Na + Ions –Dominant ECF cations –Responsible for 90-95% of osmotic pressure Regulation of Na + ions –Kidneys major route of excretion –Small quantities lost in sweat Terms –Hypernatremia –Hyponatremia

13 27-13 Mechanisms Regulating Blood Sodium

14 27-14 Mechanisms Regulating Blood Sodium

15 27-15 Abnormal Plasma Levels of Sodium Ions

16 27-16 Regulation of Chloride, Potassium, Magnesium Ions Chloride ions –Predominant anions in ECF Magnesium ions –Capacity of kidney to reabsorb is limited –Excess lost in urine –Decreased extracellular magnesium results in greater degree of reabsorption Potassium ions –Maintained in narrow range –Affect resting membrane potentials –Aldosterone increases amount secreted Terms –Hyperkalemia –Hypokalemia

17 27-17 Potassium Ion Regulation in ECF

18 27-18 Abnormal Concentration of Potassium Ions

19 27-19 Abnormal Plasma Levels of Magnesium Ions

20 27-20 Regulation of Blood Magnesium

21 27-21 Regulation of Calcium Ions Regulated within narrow range –Elevated extracellular levels prevent membrane depolarization –Decreased levels lead to spontaneous action potential generation Terms –Hypocalcemia –Hypercalcemia PTH increases Ca 2+ extracellular levels and decreases extracellular phosphate levels Vitamin D stimulates Ca 2+ uptake in intestines Calcitonin decreases extracellular Ca 2+ levels

22 27-22 Regulation of Calcium Ions

23 27-23 Regulation of Phosphate Ions Under normal conditions, reabsorption of phosphate occurs at maximum rate in the nephron An increase in plasma phosphate increases amount of phosphate in nephron beyond that which can be reabsorbed; excess is lost in urine

24 27-24 Regulation of Blood Phosphate

25 27-25 Acids and Bases and Buffers Acids –Release H + into solution Bases –Remove H + from solution Acids and bases –Grouped as strong or weak Buffers: Resist changes in pH –When H + added, buffer removes –When H + removed, buffer replaces Types of buffer systems –Carbonic acid/bicarbonate –Protein –Phosphate

26 27-26 Regulation of Acid-Base Balance

27 27-27 Regulation of Acid-Base Balance

28 27-28 Buffer Systems

29 27-29 Respiratory Regulation of Acid-Base Balance Respiratory regulation of pH is achieved through carbonic acid/bicarbonate buffer system –As carbon dioxide levels increase, pH decreases –As carbon dioxide levels decrease, pH increases –Carbon dioxide levels and pH affect respiratory centers Hypoventilation increases blood carbon dioxide levels Hyperventilation decreases blood carbon dioxide levels

30 27-30 Respiratory Regulation of Acid-Base Balance

31 27-31 Renal Regulation of Acid-Base Balance Secretion of H + into filtrate and reabsorption of HCO 3 - into ECF cause extracellular pH to increase HCO 3 - in filtrate reabsorbed Rate of H + secretion increases as body fluid pH decreases or as aldosterone levels increase Secretion of H + inhibited when urine pH falls below 4.5

32 27-32 Kidney Regulation of Acid-Base Balance

33 27-33 Hydrogen Ion Buffering

34 27-34 Acidosis and Alkalosis Acidosis: pH body fluids below 7.35 –Respiratory: Caused by inadequate ventilation –Metabolic: Results from all conditions other than respiratory that decrease pH Alkalosis: pH body fluids above 7.45 –Respiratory: Caused by hyperventilation –Metabolic: Results from all conditions other than respiratory that increase pH Compensatory mechanisms

35 27-35 Acidosis and Alkalosis


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