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Ch 15 Fluids, Electrolytes, and Acid - Base Balance

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54 Questions

What is the normal pH range of the extracellular fluid (ECF)?

7.35 to 7.45

What is the primary function of acid-base buffer systems?

To maintain a stable pH level in body fluids

What happens to the pH of blood when acid is added to it?

The pH decreases

What is the role of the kidneys in regulating acid-base balance?

To secrete H+ ions

What is the weakest acid in the bicarbonate buffer system?

Carbonic acid (H2CO3)

What is the primary source of H+ ions in the body?

All of the above

What is the role of buffers in maintaining acid-base balance?

To minimize changes in pH

What is the base member of the bicarbonate buffer system?

Bicarbonate ion (HCO3-)

What is the primary function of the bicarbonate buffer system?

To minimize H+ increase in the blood

What is the role of the protein buffer system in the body?

To release and accept H+ ions

What is the effect of a slower breathing rate on blood CO2 levels?

An increase in CO2 levels

What is the response of nephrons to a high-protein diet?

Increase H+ secretion into urine

What is the primary goal of compensation in acid-base imbalances?

To return blood pH to the normal range

What is the result of respiratory acidosis?

A decrease in CO2 expiration

What is the role of the phosphate buffer system in the body?

To regulate H+ levels

What is the effect of increased CO2 levels in the blood on carbonic acid levels?

An increase in carbonic acid levels

What is the primary function of aldosterone in regulating electrolyte balance?

Enhancing sodium reabsorption and potassium secretion in the kidneys

Which of the following hormones regulates calcium ion concentration in the body?

Calcitonin

What is the primary mechanism by which electrolytes are lost from the body?

Excretion through the kidneys

What is the term for the process by which the body regulates the concentration of electrolytes?

Electrolyte balance

Which of the following is a symptom of severe electrolyte deficiency?

Salt craving

What is the role of parathyroid hormone in regulating calcium ion concentration?

Stimulating bone resorption and increasing calcium ion concentration

What are acids in the context of acid-base balance?

Electrolytes that release hydrogen ions

How do electrolytes regulate the body's fluid balance?

By controlling the amount of water reabsorbed in the kidneys

What is the primary source of hydrogen ions in metabolic acidosis?

Lactic acid, fatty acids, and ketone bodies

What is the role of nephrons in regulating acid-base balance?

Excreting hydrogen ions

Which of the following is an example of a chemical buffer system?

Phosphate buffer system

What happens to blood pH when there is increased CO2 retention?

It decreases

What is the effect of hyperventilation on blood pH?

It increases

What is the role of ammonia in the renal excretion of hydrogen ions?

It helps transport H+ ions outside the body

What is the primary mechanism of respiratory acidosis?

Increased CO2 retention

What is the primary source of H+ ions in the body fluids?

Carbon dioxide gas

What is the result of metabolic acidosis in the body?

Decreased pH of blood

How do nephrons respond to a decrease in pH of body fluids?

They increase H+ secretion into urine

Which buffer system is mainly responsible for regulating H+ levels in the kidneys?

Phosphate buffer system

What is the effect of respiratory acidosis on blood pH?

Decreases blood pH

What is the role of the bicarbonate buffer system in the blood?

To regulate H+ levels

What is the cause of respiratory acidosis?

Deficiency of CO2 expiration

What is the primary source of hydrogen ions in the body?

Hydrolysis of proteins and amino acids

What is the effect of metabolic acidosis on the body's pH levels?

It decreases the pH levels

How do the kidneys regulate acid-base balance?

By controlling the concentration of bicarbonate ions

What is the function of buffer systems in the body?

To maintain a constant pH level

What is the effect of respiratory acidosis on the body's CO2 levels?

It increases CO2 levels

What is the role of the bicarbonate buffer system in regulating acid-base balance?

It decreases the concentration of H+ ions

What is the effect of a decrease in respiratory rate on the body's pH levels?

It decreases the pH levels

What is the source of hydrogen ions in the body during aerobic respiration of glucose?

Carbonic acid dissociation

Which of the following is a factor associated with edema?

Obstruction of lymph vessels

What is the effect of inflammation on capillaries?

They become abnormally permeable

What is the source of hydrogen ions in the body during anaerobic respiration of glucose?

Lactic acid production

What is the effect of low plasma protein concentration on blood vessels?

It decreases plasma osmotic pressure

What is the source of hydrogen ions in the body during the oxidation of sulfur-containing amino acids?

Sulfuric acid production

What is the effect of increased venous pressure on capillaries?

It increases capillary filtration

What is the source of hydrogen ions in the body during the hydrolysis of phosphoproteins and nucleic acids?

Phosphoric acid production

What is the effect of obstruction of lymph vessels on fluid movement?

It decreases fluid movement from interstitial spaces into lymph capillaries

Study Notes

Acid-Base Balance

  • Bases release hydroxide ions (OH-) when dissolved in water.
  • Acid-base balance is primarily regulated by the concentration of H+ (or pH level) in body fluids, especially Extracellular Fluid (ECF).

pH Regulation

  • Normal pH range of ECF is from 7.35 to 7.45.
  • Most H+ comes from metabolism (glycolysis, oxidation of fatty acids and amino acids, and hydrolysis of proteins).
  • Homeostasis of pH in body fluids is regulated by acid-base buffer systems (primary control), respiratory centers in brain stem, and kidney tubule secretion of H+.

Acid-Base Buffer Systems

  • Buffer systems are chemical reactions that consist of a weak acid and a weak base, to prevent rapid, drastic changes in body fluid pH.
  • One of the most carefully regulated concentrations in the body is that of H+ ion.
  • When acid (H+) is added to the blood, the pH decreases, and buffers bind some of the added H+.
  • When acid is taken away, blood becomes more alkaline (pH increases), and buffers release H+ to replace some of the acid that was lost.

Bicarbonate Buffer System

  • The pair bicarbonate/carbonic acid forms an important buffer system.
  • H2CO3 (carbonic acid) is the acid member of the pair because it can release H+.
  • HCO3- is the base member of the pair because it can accept H+.
  • This system is important because two of its components are rigorously controlled by the body: the lungs control CO2 and the kidney control HCO3-.

Hormonal Regulation of Electrolytes

  • Level of electrolytes are mainly regulated by hormones:
    • Aldosterone (from adrenal cortex) causes an increase in sodium reabsorption and potassium secretion at the kidney tubules.
    • Parathyroid hormone (PTH) from the parathyroid glands and Calcitonin (CT) from the thyroid gland regulate calcium balance.

Electrolyte Intake and Output

  • Electrolyte intake:
    • Electrolytes are usually obtained in sufficient quantities in response to hunger and thirst mechanisms.
    • In a severe electrolyte deficiency, a person may experience a salt craving.
  • Electrolyte output:
    • Electrolytes are lost through perspiration, feces, and urine.
    • The greatest electrolyte loss occurs as a result of kidney functions.
    • Quantities lost vary with temperature and exercise.

Electrolyte Balance

  • Concentrations of Na, K, and calcium ions in body fluids are very important.
  • Regulation of Na+ and K+ ions involve the secretion of Aldosterone from adrenal glands.
  • Calcitonin from the thyroid gland and Parathyroid hormone from the parathyroid glands regulate Ca+ ion concentration.

Other Buffer Systems

  • Phosphate buffer system produces sodium hydrogen phosphates (NaH2PO4 and Na2HPO4) to regulate H+ levels, mainly in kidney tubules and erythrocytes.
  • Protein buffer system relies on the carboxylic acid group of amino acids to release H+, and the amino group to accept H+, mainly inside body cells and in blood plasma.

Respiratory and Renal Regulation

  • Respiratory centers in the pons and medulla oblongata regulate the rate and depth of breathing, which controls the amount of carbon dioxide gas (CO2) remained in the blood and body fluid.
  • Nephrons react to the pH of body fluids and regulate the secretion of H+ into urine.
  • Tubule H secretion and reabsorption of filtered HCO3- also help regulate pH levels.

Compensation

  • Compensation is a series of physiological responses that react to acid-base imbalances, by returning blood pH to the normal range (7.35 – 7.45).
  • Respiratory acidosis and respiratory alkalosis are primary disorders of CO2 pressure in the lungs.

Acid-Base Balance

  • Acid-base balance is primarily regulated by the concentration of H+ (or the pH level) in body fluids, especially extracellular fluid (ECF)
  • Normal pH range of ECF is from 7.35 to 7.45
  • Most H+ comes from metabolism -- glycolysis, oxidation of fatty acids and amino acids, and hydrolysis of proteins

Acid-Base Buffer Systems

  • Bicarbonate buffer system produces carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3) to minimize H+ increase, mainly in the blood
  • Phosphate buffer system produces sodium hydrogen phosphates (NaH2PO4 and Na2HPO4) to regulate H+ levels, mainly in kidney tubules and erythrocytes
  • Protein buffer system relies on the carboxylic acid group of amino acids to release H+, and the amino group to accept H+, mainly inside body cells and in blood plasma

Respiratory and Metabolic Acidosis and Alkalosis

  • Respiratory acidosis: increased CO2 retention due to hypoventilation, resulting in a fall in blood pH to below normal
  • Metabolic acidosis: increased production of acids such as lactic acid, fatty acids, and ketone bodies, or loss of blood bicarbonate, resulting in a fall in blood pH to below normal
  • Respiratory alkalosis: a rise in blood pH due to loss of CO2 and carbonic acid through hyperventilation
  • Metabolic alkalosis: a rise in blood pH produced by loss of acids or by excessive accumulation of bicarbonate base

Compensatory Mechanisms

  • Renal mechanisms: nephrons secrete more H+ to correct acidosis and secrete less H+ to correct alkalosis
  • Respiratory compensation: the respiratory center regulates the rate and depth of breathing to control pH by regulating the rate and depth of breathing
  • Chemical buffer systems act rapidly and are the first line of defense against pH shift
  • Physiological buffer systems (respiratory mechanism CO2 excretion) and renal mechanisms (H+ excretion) act slowly and are the second line of defense against pH shift

Learn about acid-base balance, pH regulation, and the role of electrolytes, metabolism, and homeostasis in maintaining normal pH levels in body fluids.

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