CH15 Fluid, Electrolyte, and Acid-Base Balance

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Questions and Answers

Which hormone increases sodium reabsorption and potassium secretion at the kidney tubules?

Aldosterone (correct)

Adrenaline

Calcitonin

Parathyroid hormone

What is the primary way the body obtains electrolytes?

In response to hunger and thirst mechanisms (correct)

Through kidney function

Through sweat glands

Through supplements

What is the greatest route of electrolyte loss in the body?

Kidney function (correct)

Perspiration

Urine

Feces

What is the effect of parathyroid hormone on bone cells?

It increases activity in bone-resorbing cells Signup and view all the answers

What is the primary function of calcitonin?

To regulate calcium balance Signup and view all the answers

What is an acid in the context of electrolyte balance?

An electrolyte that releases hydrogen ions when dissolved in water Signup and view all the answers

What happens when there is a severe electrolyte deficiency?

A person may experience a salt craving Signup and view all the answers

What is the effect of aldosterone on potassium ions in the kidney?

It increases potassium secretion Signup and view all the answers

What is the primary function of electrolytes in the body?

To control osmosis between body compartments Signup and view all the answers

Which electrolyte is involved in nerve impulse transmission, muscle contraction, and creation of osmotic pressure?

Na+ Signup and view all the answers

What is the role of Cl- in the body?

Regulating osmotic pressure between body compartments Signup and view all the answers

Which electrolyte is the most abundant ion in the body?

Ca++ Signup and view all the answers

What is the function of HPO42- in the body?

Required for synthesis of nucleic acids and ATP, and for buffering reactions Signup and view all the answers

What is the role of K+ in the body?

Maintaining fluid volume and regulating pH Signup and view all the answers

What is the function of electrolytes in maintaining acid-base balance?

Helping to regulate pH levels Signup and view all the answers

What is the general definition of electrolytes?

Chemical substances that release cations and anions when dissolved in water Signup and view all the answers

What percentage of body fluids are located outside of body cells?

37% Signup and view all the answers

What type of fluid is responsible for 80% of ECF?

Interstitial fluid Signup and view all the answers

What is the main function of the cell membrane in maintaining fluid balance?

It is selectively permeable Signup and view all the answers

What are the two main forces behind molecular movement between body compartments?

Osmotic pressure and hydrostatic pressure Signup and view all the answers

What is the daily water intake of a normal adult?

2,500 ml Signup and view all the answers

What is the percentage of body weight that is made up of water?

45% to 75% Signup and view all the answers

What is the term for the proper levels of water and electrolytes being in the various body compartments according to their needs?

Fluid balance Signup and view all the answers

Which of the following is NOT a type of extracellular fluid?

Intracellular fluid Signup and view all the answers

What do bases release when they are dissolved in water?

Hydroxide ions (OH-) Signup and view all the answers

What is the primary regulator of acid-base balance in the body?

The concentration of H+ (or the pH level) Signup and view all the answers

What is the normal pH range of ECF in the body?

7.35 to 7.45 Signup and view all the answers

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

All of the above Signup and view all the answers

What is the function of acid-base buffer systems in the body?

To prevent rapid, drastic changes in body fluid pH Signup and view all the answers

What happens when acid is added to the blood?

The pH decreases Signup and view all the answers

What is the role of the bicarbonate ion (HCO3-) in the bicarbonate buffer system?

To convert a strong acid into a weak acid Signup and view all the answers

What is the role of the kidney in the regulation of acid-base balance?

To control the concentration of HCO3- Signup and view all the answers

What is the source of H+ in aerobic respiration of glucose?

Carbonic acid dissociation Signup and view all the answers

What is the effect of low plasma protein concentration on fluid movement in capillaries?

Decreased fluid enters venular end of capillaries by osmosis Signup and view all the answers

What is the result of obstruction of lymph vessels?

Decreased fluid movement from interstitial spaces into lymph capillaries Signup and view all the answers

What is the effect of increased venous pressure on fluid movement in capillaries?

Increased capillary filtration Signup and view all the answers

What is the effect of inflammation on capillary permeability?

Capillaries become more permeable Signup and view all the answers

What is the source of H+ in the oxidation of sulfur-containing amino acids?

Sulfuric acid Signup and view all the answers

Study Notes

Body Fluids

A typical adult body contains approximately 40 L of body fluids, with 25 L (63%) located inside body cells (intracellular fluid, ICF) and 15 L (37%) located outside of body cells (extracellular fluid, ECF)
ECF consists of 80% interstitial fluid and 20% blood plasma
ICF is mostly water and rich in K+, Mg++, HPO42-, SO42-, and protein anions
ECF contains more Na+, Cl-, HCO3-, and Ca++
The cell membrane is selectively permeable, maintaining a relatively unchanged distribution of substances in different body fluids

Fluid Balance

Fluid balance refers to the proper levels of water and electrolytes in the various body compartments according to their needs
Osmotic pressure and hydrostatic pressure are the main forces behind molecular movement between body compartments

Water Balance

Water is the most abundant constituent in the body, varying from 45% to 75% of body weight
Water balance occurs when water intake equals water output
A normal adult consumes about 2,500 ml of water daily, including 1,500 ml in beverages, 750 ml in food, and 250 ml from cellular respiration and anabolic metabolism

Electrolyte Balance

Electrolytes are chemical substances that release cations and anions when dissolved in water
Electrolytes serve four primary functions in the body:
- As essential minerals (e.g., iodine, calcium)
- Controlling osmosis between body compartments by establishing proper osmotic pressure (e.g., sodium, chloride)
- Helping maintain acid-base balance (e.g., hydrogen ion, bicarbonate ion)
- Carrying electrical current that allows the production of action potentials (e.g., sodium, potassium)
The most important electrolytes include Na+, K+, Cl-, Ca++, and HPO42-

Regulation of Electrolytes

Na+ is the most abundant extracellular cation, involved in nerve impulse transmission, muscle contraction, and creation of osmotic pressure
Cl- is a major extracellular anion, involved in regulating osmotic pressure, forming HCI in the stomach, and involved in the "chloride shift" process in blood
K+ is the most abundant cation in ICF, involved in maintaining fluid volume, nerve impulse transmission, muscle contraction, and regulating pH
Ca++ is the most abundant ion in the body, located mainly in ECF, and is a major structural component of bones and teeth
HPO42- is an important intracellular anion, another major structural component of bones and teeth, and is required for synthesis of nucleic acids and ATP, and for buffering reactions
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

Acid-Base Balance

Acids are electrolytes that release hydrogen ions (H+) when dissolved in water
Bases are electrolytes that release hydroxide ions (OH-) when dissolved in water
Acid-base balance is primarily regulated by the concentration of H+ (or the pH level) in body fluids, especially ECF
Normal pH range of ECF is from 7.35 to 7.45
Most H+ comes from metabolism, including 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, respiratory centers in the brain stem, and by kidney tubule secretion of H+

Acid-Base Buffer Systems

Chemical acid-base buffer systems, such as the bicarbonate buffer system, help regulate pH levels
The bicarbonate buffer system is important because two of its components are rigorously controlled by the body: the lungs control CO2 and the kidney control HCO3-

Sources of H+

Aerobic respiration of glucose produces CO2, which reacts with water to form carbonic acid
Anaerobic respiration of glucose produces lactic acid
Incomplete oxidation of fatty acids releases acidic ketone bodies
Oxidation of sulfur-containing amino acids produces sulfuric acid
Hydrolysis of phosphoproteins and nucleic acids gives rise to phosphoric acid

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Description

This quiz covers the basics of body fluids, including intracellular and extracellular fluids, as well as their composition and function. It also touches on electrolyte and acid-base balance.