Chemistry, Solutions, and Acid/Base Balance

Chemistry, Solutions, and Acid/Base Balance

Water is CohesiveWater is Cohesive

Concentrations of SolutionsConcentrations of Solutions

% solutions Molarity Osmolarity Tonicity Equivalents

% solutions Molarity Osmolarity Tonicity Equivalents

RBCs in Different SolutionsRBCs in Different Solutions

ureaurea

DiffusionDiffusion

Diffusion FactorsDiffusion Factors

Size of particle Concentration gradient Temperature Surface area Medium

Size of particle Concentration gradient Temperature Surface area Medium

Fluid CompartmentsFluid Compartments

Figure 26.1

Electrolyte Composition of Body Fluids

Electrolyte Composition of Body Fluids

Figure 26.2

Continuous Mixing of

Body Fluids

Continuous Mixing of

Body Fluids

Figure 26.3

Water Balance and ECF Osmolality

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%)

Water Balance and ECF Osmolality

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)

Water Intake and OutputWater Intake and Output

Figure 26.4

Regulation of Water Intake: Thirst

Mechanism

Regulation of Water Intake: Thirst

Mechanism

Figure 26.5

Figure 26.6

Mechanisms and

Consequences of ADH Release

Mechanisms and

Consequences of ADH Release

Figure 26.7a

Disorders of Water Balance: Dehydration

Disorders of Water Balance: Dehydration

Excessive loss of H2O from ECF

1 2 3ECF osmotic pressure rises

Cells lose H2O to ECF by osmosis; cells shrink

(a) Mechanism of dehydration

Figure 26.7b

Disorders of Water Balance: Hypotonic Hydration

Disorders of Water Balance: Hypotonic Hydration

Excessive H2O enters the ECF

1 2 ECF osmotic pressure falls

3 H2O moves into cells by osmosis; cells swell

(b) Mechanism of hypotonic hydration

Regulation of Sodium Balance:

Aldosterone

Regulation of Sodium Balance:

Aldosterone

Figure 26.8

Figure 26.10

Mechanisms and

Consequences of ANP Release

Mechanisms and

Consequences of ANP Release

pHpH

Acid-Base BalanceAcid-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)

Hydrogen Ion RegulationHydrogen 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

Chemical Buffer SystemsChemical 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

Physiological Buffer SystemsPhysiological 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

CO2 + H2O H2CO3 H+ + HCO3¯

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

CO2 + H2O H2CO3 H+ + HCO3¯

Renal Mechanisms of Acid-Base Balance

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

Respiratory Acidosis and Alkalosis

Respiratory Acidosis and Alkalosis

Result from failure of the respiratory system PCO2 is the single most important indicator of

respiratory inadequacy PCO2 levels

Normal PCO2 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 PCO2 is the single most important indicator of

respiratory inadequacy PCO2 levels

Normal PCO2 fluctuates between 35 and 45 mm Hg

Values above 45 mm Hg signal respiratory acidosis Values below 35 mm Hg indicate respiratory

alkalosis

Metabolic AcidosisMetabolic 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

Metabolic AlkalosisMetabolic 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

Respiratory and Renal Compensations

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