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Chemistry, Solutions, and Acid/Base Balance
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Water is Cohesive
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Concentrations of Solutions % solutions Molarity Osmolarity Tonicity Equivalents % solutions Molarity Osmolarity Tonicity Equivalents
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RBCs in Different Solutions
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urea
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Diffusion
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Diffusion Factors Size of particle Concentration gradient Temperature Surface area Medium Size of particle Concentration gradient Temperature Surface area Medium
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Fluid Compartments Figure 26.1
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Electrolyte Composition of Body Fluids Figure 26.2
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Continuous Mixing of Body Fluids Figure 26.3
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Water Balance and ECF Osmolality To remain properly hydrated, water intake must equal water output Water intake sources Ingested fluid (60%) and solid food (30%) Metabolic water or water of oxidation (10%) To remain properly hydrated, water intake must equal water output Water intake sources Ingested fluid (60%) and solid food (30%) Metabolic water or water of oxidation (10%)
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Water Balance and ECF Osmolality Water output Urine (60%) and feces (4%) Insensible losses (28%), sweat (8%) Increases in plasma osmolality trigger thirst and release of antidiuretic hormone (ADH) Water output Urine (60%) and feces (4%) Insensible losses (28%), sweat (8%) Increases in plasma osmolality trigger thirst and release of antidiuretic hormone (ADH)
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Water Intake and Output Figure 26.4
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Regulation of Water Intake: Thirst Mechanism Figure 26.5
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Figure 26.6 Mechanisms and Consequences of ADH Release
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Figure 26.7a Disorders of Water Balance: Dehydration Excessive loss of H 2 O from ECF 1 2 3 ECF osmotic pressure rises Cells lose H 2 O to ECF by osmosis; cells shrink (a) Mechanism of dehydration
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Figure 26.7b Disorders of Water Balance: Hypotonic Hydration Excessive H 2 O enters the ECF 1 2 ECF osmotic pressure falls 3 H 2 O moves into cells by osmosis; cells swell (b) Mechanism of hypotonic hydration
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Regulation of Sodium Balance: Aldosterone Figure 26.8
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Figure 26.10 Mechanisms and Consequences of ANP Release
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pH
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Acid-Base Balance Normal pH of body fluids Arterial blood is 7.4 Venous blood and interstitial fluid is 7.35 Intracellular fluid is 7.0 Alkalosis or alkalemia – arterial blood pH rises above 7.45 Acidosis or acidemia – arterial pH drops below 7.35 (physiological acidosis) Normal pH of body fluids Arterial blood is 7.4 Venous blood and interstitial fluid is 7.35 Intracellular fluid is 7.0 Alkalosis or alkalemia – arterial blood pH rises above 7.45 Acidosis or acidemia – arterial pH drops below 7.35 (physiological acidosis)
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Hydrogen Ion Regulation Concentration of hydrogen ions is regulated sequentially by: Chemical buffer systems – act within seconds The respiratory center in the brain stem – acts within 1-3 minutes Renal mechanisms – require hours to days to effect pH changes Concentration of hydrogen ions is regulated sequentially by: Chemical buffer systems – act within seconds The respiratory center in the brain stem – acts within 1-3 minutes Renal mechanisms – require hours to days to effect pH changes
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Chemical Buffer Systems One or two molecules that act to resist pH changes when strong acid or base is added Three major chemical buffer systems Bicarbonate buffer system Phosphate buffer system Protein buffer system Any drifts in pH are resisted by the entire chemical buffering system One or two molecules that act to resist pH changes when strong acid or base is added Three major chemical buffer systems Bicarbonate buffer system Phosphate buffer system Protein buffer system Any drifts in pH are resisted by the entire chemical buffering system
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Physiological Buffer Systems The respiratory system regulation of acid- base balance is a physiological buffering system There is a reversible equilibrium between: Dissolved carbon dioxide and water Carbonic acid and the hydrogen and bicarbonate ions CO 2 + H 2 O H 2 CO 3 H + + HCO 3 ¯ The respiratory system regulation of acid- base balance is a physiological buffering system There is a reversible equilibrium between: Dissolved carbon dioxide and water Carbonic acid and the hydrogen and bicarbonate ions CO 2 + H 2 O H 2 CO 3 H + + HCO 3 ¯
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Renal Mechanisms of Acid-Base Balance Only the kidneys can rid the body of metabolic acids (phosphoric, uric, and lactic acids and ketones) and prevent metabolic acidosis The ultimate acid-base regulatory organs are the kidneys Only the kidneys can rid the body of metabolic acids (phosphoric, uric, and lactic acids and ketones) and prevent metabolic acidosis The ultimate acid-base regulatory organs are the kidneys
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Respiratory Acidosis and Alkalosis Result from failure of the respiratory system P CO2 is the single most important indicator of respiratory inadequacy P CO2 levels Normal P CO2 fluctuates between 35 and 45 mm Hg Values above 45 mm Hg signal respiratory acidosis Values below 35 mm Hg indicate respiratory alkalosis Result from failure of the respiratory system P CO2 is the single most important indicator of respiratory inadequacy P CO2 levels Normal P CO2 fluctuates between 35 and 45 mm Hg Values above 45 mm Hg signal respiratory acidosis Values below 35 mm Hg indicate respiratory alkalosis
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Metabolic Acidosis All pH imbalances except those caused by abnormal blood carbon dioxide levels Metabolic acid-base imbalance – bicarbonate ion levels above or below normal (22-26 mEq/L) Metabolic acidosis is the second most common cause of acid-base imbalance All pH imbalances except those caused by abnormal blood carbon dioxide levels Metabolic acid-base imbalance – bicarbonate ion levels above or below normal (22-26 mEq/L) Metabolic acidosis is the second most common cause of acid-base imbalance
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Metabolic Alkalosis Rising blood pH and bicarbonate levels indicate metabolic alkalosis Typical causes are: Vomiting of the acid contents of the stomach Intake of excess base (e.g., from antacids) Constipation, in which excessive bicarbonate is reabsorbed Rising blood pH and bicarbonate levels indicate metabolic alkalosis Typical causes are: Vomiting of the acid contents of the stomach Intake of excess base (e.g., from antacids) Constipation, in which excessive bicarbonate is reabsorbed
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Respiratory and Renal Compensations Acid-base imbalance due to inadequacy of a physiological buffer system is compensated for by the other system The respiratory system will attempt to correct metabolic acid-base imbalances The kidneys will work to correct imbalances caused by respiratory disease Acid-base imbalance due to inadequacy of a physiological buffer system is compensated for by the other system The respiratory system will attempt to correct metabolic acid-base imbalances The kidneys will work to correct imbalances caused by respiratory disease
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