The fluids in your body are composed of water and dissolved substances, including electrolytes, which are crucial for body function. Your goals for learning are: To list the general functions and importance of water and electrolytes in the body. To identify the fluid compartments and the relative concentrations of electrolytes within those fluid spaces. What you need to know: The definition of osmosis which is the diffusion of water through a selectively permeable membrane from a higher water concentration (and lower solute concentration) to a lower water concentration (and higher solute concentration). Membrane transport mechanisms We ingest water and electrolytes through the gastrointestinal, or GI, tract. Fluids are absorbed into the plasma in the intestine. The fluids circulate within the plasma, bathing the cells in the body. The kidneys remove excess ions and water from the body through the urine. Although water is also lost at other sites. Water performs several important functions in the body. Water helps maintain body temperature. When water vaporizes off the skin, it takes large quantities of heat with it. This process cools the body temperature down. Because water has a high heat capacity, it can absorb and release large quantities of heat before significantly changing temperature. Our bodies are composed of 50 to 70 percent water and that large percentage of water holds heat in the body and helps prevent fluctuation in body temperature. Water acts as a protective cushion in amniotic fluid and cerebral-spinal fluid. Water acts as a lubricant in the serous fluids, joints, and gastrointestinal tract. [EATING SOUND] Water is the reactant for hydrolysis reactions that occur in the body. Starch is hydrolyzed in the mouth by the enzyme salivary amylase. With the help of this enzyme, water molecules are added to the bonds between the glucose unit in the starch hydrolyzing the starch to glucose. Note that water can also be formed during some chemical reactions in the body such as the reactions that produce metabolic water. Water acts as a solvent to dissolve molecules and ions in the body. For example, if you eat a salty pretzel, the water in your saliva will dissolve the salt. Water is a polar molecule. When water dissolves ions, the partial negative charge on the oxygen attracts positive ions such as sodium and the partial positive charge on the hydrogen attracts negative ions such as chloride. Except for the salts deposited in bone and teeth, most other ions in the body are dissolved because of water’s ability to act as a solvent. Water within cells is an important solvent. It dissolves many of the proteins and other solutes. We are now looking at a blood vessel. Because of water’s ability to dissolve ions and molecules within the body fluids, water functions as a medium for the delivery of nutrients and the removal of wastes from the cells through the plasma. The percentage of water in a person depends on the amount of fat tissue which is only about 20 percent water compared to lean body mass or muscle mass which is about 65 percent water. Let’s determine the approximate percentage of water in the bodies of each of these people. A healthy young man who is muscular and does not have a lot of fat in his body is about 60 percent water. Newborns have the highest percentage of water in their bodies at 73 percent. A healthy young woman naturally has more fat and less muscle than a man and is about 50 percent water. The more fat a person has in his or her body, the less water is present. Older people tend to have less lean body mass and therefore contain less water. Water along with its dissolved solutes occupies three main compartments within the body. Intracellular fluid is the fluid within cells, it is also known as cytosol. Extracellular fluid is the fluid found outside of cells. There are two major kinds of extracellular fluid. Interstitial fluid is the fluid surrounding the cells. Plasma is the fluid component of the blood. Let’s consider a 70-kilogram man. 60 percent of his weight or approximately 40 liters is fluid. Approximately 62% of the body’s fluid is intracellular. [TAP WATER SOUND] Approximately 30 percent of the body’s fluid is interstitial. Approximately 8 percent of the body’s fluid is plasma. You are looking at plasma, a typical body fluid. The term “body fluid” refers to the water in the body and all the dissolved substances which are also known as solutes. Since the water dissolves the solutes, it is the solvent. A typical body fluid contains electrolytes also known as ions. Proteins are considered to be colloids when dispersed in body fluids. Compared to simple ions, proteins are huge molecules. Because they bear a negative charge, we will consider them to be electrolytes. Non-electrolytes are uncharged molecules found in body fluids. Glucose is an example of a non-electrolyte. Blood cells do not dissolve in water. They are suspended particles and are not considered to be a part of the body fluid. Electrolytes are charged particles or ions that are dissolved in body fluids. The major positive ions, or cations, in body fluids, are; Sodium ion, Potassium ion, Calcium ion, and Magnesium ion. The major negative ions, or anions, in body fluids, are; chloride ion, bicarbonate ion, phosphate ions, sulfate ion, organic acids, and proteins. Each fluid compartment needs just the right types and levels of electrolytes for proper functioning of neurons, muscle cells, and other cells in the body. The electrolyte composition of extracellular fluids and intracellular fluids have significant differences. Filling in the pie graph will help illustrate these differences. In addition to sodium, extracellular fluid contains the positive ions; potassium, calcium, and magnesium. The intracellular fluid contains the positive ions; potassium, sodium, and magnesium. The extracellular fluid contains the following negative ions: chloride, protein, bicarbonate, phosphate, organic acid, and sulfate. The intracellular fluid contains the negative ions; phosphate, protein, bicarbonate, chloride, and sulfate. The composition of interstitial fluid is almost identical to that of plasma, except for one negative electrolyte, protein. There is very little protein in interstitial fluid. To summarize; the major positive ion of the extracellular fluid is sodium and its major negative ion is chloride. The major positive ion of the intracellular fluid is potassium and its major negative ions are protein and phosphates. Let’s count the number of positive and negative ions, or particles, in this sample of intracellular fluid and see if the number of positive ions equals the number of negative ions. There are 9 positive ions and 6 negative ions here, so the number of ions are not equal. Now let’s count the number of positive and negative charges in this sample of intracellular fluid. There are 11 positive charges and 11 negative charges in this intracellular fluid. The laws of chemistry dictate that within a fluid compartment, the total number of positive charges must be equal to the total number of negative charges. Even though there are six negative ions and nine positive ions here, the charges balance because the individual ions have different charges, there may not be the same number of positive and negative ions in the compartment, the charges will always balance. Now, let’s look at a few of the many important functions electrolytes perform in the body. Electrolytes serve as cofactors for enzymes. A very important reaction in the body occurs when carbon dioxide and water form carbonic acid. We can speed up this reaction with the enzyme carbonic anhydrase. Cofactors are non-protein substances that act along with enzymes to speed up reactions in the body. Calcium, Magnesium, and other cations such as Zinc can serve as cofactors for enzymes. Zinc is a cofactor for this enzyme. Let’s add it the enzyme. This enzymatic reaction shown here cannot occur without a zinc ion present. Many other enzymes in the body require positive metal ions as cofactors in order to function. Electrolytes in the form of sodium and potassium ions also contribute to membrane potential in all cells and are responsible for action potentials in neuron and muscle cells. [BODY ORGAN SOUND] Calcium ions are important electrolytes because they are involved in the secretion and action of hormones and neurotransmitters. The blue balls represent vesicles containing neurotransmitters. Calcium is also involved in the contraction of muscles including the heart. Some electrolytes such as bicarbonate phosphate and protein help maintain acid /base balance. By pumping sodium out of the cell, the sodium potassium pump uses ATP to keep the concentration of sodium low in the cells. During secondary active transport, some transport proteins will allow sodium to diffuse from areas of high to low concentration and drag with it a molecule or another ion such as glucose seen here from an area of lower to higher concentration. Glucose enters the proximal convoluted tubular cells of the kidney tubulars and the intestine by secondary active transport. Finally, electrolytes, including proteins, also play a major role in promoting the movement of water between fluid compartments through osmosis. Let’s take a closer look at what happens during osmosis. Osmosis is the movement of water across a membrane from the side that has more water and therefore less solute to the side that has less water and therefore more solute. When there are equal amounts of water particles on either side of the membrane, water moves freely back and forth across the membrane in both directions at the same rate. We say that the two solutions are isotonic, meaning that they have the same total concentration of non-penetrating solute particles. Let’s see what happens when more solute particles are added to the right side of the container. Now more solute is present on the right side and it is hypertonic compared to the left side. Because less solute is present on the left side, we say that solution is hypotonic compared to the right side. Note that if you increase the concentration of solute, you decrease the concentration of water. Water still moves freely across the membrane in both directions. However less water will move from right to left because the higher concentration of water on the left side creates a greater chance of a collision between a water molecule and a channel on the left side. As a result, more water will move from the left side to the right side of the container. Let’s see how solutions of different tonicity affect real cells. In a hypertonic solution, water moves out of cells and they shrink, or crenate. In a hypertonic solution, water moves into cells and they expand. We measure the ability of a solution to cause osmosis in terms of osmotic pressure which is expressed in millimeters of mercury, a unit of pressure. Osmotic pressure is defined as the external pressure applied to the top of the fluid to prevent osmosis from occurring. The greater the number of solute particles dissolved in solution, the higher the osmotic pressure. Here we see a patient ready to receive an intravenous solution. Normally patients are given an isotonic IV solution. In this patient, the hypertonic and hypotonic IVs are contraindicated. Let’s see what happens to this patient’s blood cells when each IV is given. If we put a red blood cell in a hypotonic solution, the cell will expand. If too much water enters the cell, it could eventually undergo hemolysis or break open. When a cell is placed in a more dilute solution, more water hits water channels on the outside of the membrane than on the inside causing more water to move to the into the cell. This is why hypotonic IV solutions are only used in specific clinical situations. If we put a red blood cell in a hypertonic solution, the cell will shrink, or crenate because more water hits water channels in the membrane on the inside of the cell than on the outside of the cell. There is a net flow of water out of the cell that causes the cell to shrink. This is why hypertonic IV solutions are only used in specific clinical situations. If we put a red blood cell in an isotonic solution, the cell volume will remain constant. Here’s a summary of what we’ve covered. Fluids are composed of water and all the substances, or solutes, dissolved in the water in the body. Most fluids within the body exist in three major compartments: intracellular, plasma, and interstitial. The interstitial compartment and the plasma are the extracellular compartments. Within a solution, positive and negative charges must balance regardless of the number of ions present. The concentrations of dissolved ions, or electrolytes, in the intracellular compartment are very different than the concentrations of electrolytes in the extracellular compartment. Both water and electrolytes have many important functions in the body. Osmosis is the movement of water across a membrane from the side that has more water to the side that has less water.
Table of contents
- 1. Introduction to Anatomy & Physiology5h 40m
- What is Anatomy & Physiology?20m
- Levels of Organization13m
- Variation in Anatomy & Physiology12m
- Introduction to Organ Systems27m
- Homeostasis9m
- Feedback Loops11m
- Feedback Loops: Negative Feedback19m
- Feedback Loops: Positive Feedback11m
- Anatomical Position7m
- Introduction to Directional Terms3m
- Directional Terms: Up and Down9m
- Directional Terms: Front and Back6m
- Directional Terms: Body Sides12m
- Directional Terms: Limbs6m
- Directional Terms: Depth Within the Body4m
- Introduction to Anatomical Terms for Body Regions3m
- Anatomical Terms for the Head and Neck8m
- Anatomical Terms for the Front of the Trunk8m
- Anatomical Terms for the Back9m
- Anatomical Terms for the Arm and Hand9m
- Anatomical Terms for the Leg and Foot15m
- Review- Using Anatomical Terms and Directions12m
- Abdominopelvic Quadrants and Regions19m
- Anatomical Planes & Sections17m
- Organization of the Body: Body Cavities13m
- Organization of the Body: Serous Membranes14m
- Organization of the Body: Serous Membrane Locations8m
- Organization of the Body: Thoracic Cavity8m
- Organization of the Body: Abdominopelvic Cavity12m
- 2. Cell Chemistry & Cell Components12h 37m
- Atoms- Smallest Unit of Matter57m
- Isotopes39m
- Introduction to Chemical Bonding19m
- Covalent Bonds40m
- Noncovalent Bonds5m
- Ionic Bonding37m
- Hydrogen Bonding19m
- Introduction to Water7m
- Properties of Water- Cohesion and Adhesion7m
- Properties of Water- Density8m
- Properties of Water- Thermal14m
- Properties of Water- The Universal Solvent17m
- Acids and Bases12m
- pH Scale21m
- Carbon8m
- Functional Groups9m
- Introduction to Biomolecules2m
- Monomers & Polymers11m
- Carbohydrates23m
- Proteins25m
- Nucleic Acids34m
- Lipids28m
- Microscopes10m
- Prokaryotic & Eukaryotic Cells26m
- Introduction to Eukaryotic Organelles16m
- Endomembrane System: Protein Secretion34m
- Endomembrane System: Digestive Organelles15m
- Mitochondria & Chloroplasts21m
- Endosymbiotic Theory10m
- Introduction to the Cytoskeleton10m
- Cell Junctions8m
- Biological Membranes10m
- Types of Membrane Proteins7m
- Concentration Gradients and Diffusion9m
- Introduction to Membrane Transport14m
- Passive vs. Active Transport13m
- Osmosis33m
- Simple and Facilitated Diffusion17m
- Active Transport30m
- Endocytosis and Exocytosis15m
- 3. Energy & Cell Processes10h 7m
- Introduction to Energy15m
- Laws of Thermodynamics15m
- Chemical Reactions9m
- ATP20m
- Enzymes14m
- Enzyme Activation Energy9m
- Enzyme Binding Factors9m
- Enzyme Inhibition10m
- Introduction to Metabolism8m
- Redox Reactions15m
- Introduction to Cellular Respiration22m
- Types of Phosphorylation11m
- Glycolysis19m
- Pyruvate Oxidation8m
- Krebs Cycle16m
- Electron Transport Chain14m
- Chemiosmosis7m
- Review of Aerobic Cellular Respiration19m
- Fermentation & Anaerobic Respiration23m
- Introduction to Cell Division22m
- Organization of DNA in the Cell17m
- Introduction to the Cell Cycle7m
- Interphase18m
- Phases of Mitosis48m
- Cytokinesis16m
- Cell Cycle Regulation18m
- Review of the Cell Cycle7m
- Cancer13m
- Introduction to DNA Replication22m
- DNA Repair7m
- Central Dogma7m
- Introduction to Transcription20m
- Steps of Transcription19m
- Genetic Code25m
- Introduction to Translation30m
- Steps of Translation23m
- Post-Translational Modification6m
- 4. Tissues & Histology10h 3m
- Introduction to Tissues & Histology16m
- Introduction to Epithelial Tissue24m
- Characteristics of Epithelial Tissue37m
- Structural Naming of Epithelial Tissue19m
- Simple Epithelial Tissues1h 2m
- Stratified Epithelial Tissues55m
- Identifying Types of Epithelial Tissue32m
- Glandular Epithelial Tissue26m
- Introduction to Connective Tissue36m
- Classes of Connective Tissue8m
- Introduction to Connective Tissue Proper40m
- Connective Tissue Proper: Loose Connective Tissue56m
- Connective Tissue Proper: Dense Connective Tissue49m
- Specialized Connective Tissue: Cartilage44m
- Specialized Connective Tissue: Bone12m
- Specialized Connective Tissue: Blood9m
- Introduction to Muscle Tissue7m
- Types of Muscle Tissue45m
- Introduction to Nervous Tissue8m
- Nervous Tissue: The Neuron8m
- 5. Integumentary System2h 20m
- 6. Bones & Skeletal Tissue2h 16m
- An Introduction to Bone and Skeletal Tissue18m
- Gross Anatomy of Bone: Compact and Spongy Bone7m
- Gross Anatomy of Bone: Periosteum and Endosteum11m
- Gross Anatomy of Bone: Bone Marrow8m
- Gross Anatomy of Bone: Short, Flat, and Irregular Bones5m
- Gross Anatomy of Bones - Structure of a Long Bone23m
- Microscopic Anatomy of Bones - Bone Matrix9m
- Microscopic Anatomy of Bones - Bone Cells25m
- Microscopic Anatomy of Bones - The Osteon17m
- Microscopic Anatomy of Bones - Trabeculae9m
- 7. The Skeletal System2h 35m
- 8. Joints2h 17m
- 9. Muscle Tissue2h 33m
- 10. Muscles1h 11m
- 11. Nervous Tissue and Nervous System1h 35m
- 12. The Central Nervous System1h 6m
- 13. The Peripheral Nervous System1h 26m
- Introduction to the Peripheral Nervous System5m
- Organization of Sensory Pathways16m
- Introduction to Sensory Receptors5m
- Sensory Receptor Classification by Modality6m
- Sensory Receptor Classification by Location8m
- Proprioceptors7m
- Adaptation of Sensory Receptors8m
- Introduction to Reflex Arcs13m
- Reflex Arcs15m
- 14. The Autonomic Nervous System1h 38m
- 15. The Special Senses2h 41m
- 16. The Endocrine System2h 48m
- 17. The Blood1h 22m
- 18. The Heart1h 42m
- 19. The Blood Vessels3h 35m
- 20. The Lymphatic System3h 16m
- 21. The Immune System14h 37m
- Introduction to the Immune System10m
- Introduction to Innate Immunity17m
- Introduction to First-Line Defenses5m
- Physical Barriers in First-Line Defenses: Skin13m
- Physical Barriers in First-Line Defenses: Mucous Membrane9m
- First-Line Defenses: Chemical Barriers24m
- First-Line Defenses: Normal Microbiota7m
- Introduction to Cells of the Immune System15m
- Cells of the Immune System: Granulocytes28m
- Cells of the Immune System: Agranulocytes26m
- Introduction to Cell Communication5m
- Cell Communication: Surface Receptors & Adhesion Molecules16m
- Cell Communication: Cytokines27m
- Pattern Recognition Receptors (PRRs)48m
- Introduction to the Complement System24m
- Activation Pathways of the Complement System23m
- Effects of the Complement System23m
- Review of the Complement System13m
- Phagocytosis17m
- Introduction to Inflammation18m
- Steps of the Inflammatory Response28m
- Fever8m
- Interferon Response25m
- Review Map of Innate Immunity
- Introduction to Adaptive Immunity32m
- Antigens12m
- Introduction to T Lymphocytes38m
- Major Histocompatibility Complex Molecules20m
- Activation of T Lymphocytes21m
- Functions of T Lymphocytes25m
- Review of Cytotoxic vs Helper T Cells13m
- Introduction to B Lymphocytes27m
- Antibodies14m
- Classes of Antibodies35m
- Outcomes of Antibody Binding to Antigen15m
- T Dependent & T Independent Antigens21m
- Clonal Selection20m
- Antibody Class Switching17m
- Affinity Maturation14m
- Primary and Secondary Response of Adaptive Immunity21m
- Immune Tolerance28m
- Regulatory T Cells10m
- Natural Killer Cells16m
- Review of Adaptive Immunity25m
- 22. The Respiratory System3h 20m
- 23. The Digestive System2h 5m
- 24. Metabolism and Nutrition4h 0m
- Essential Amino Acids5m
- Lipid Vitamins19m
- Cellular Respiration: Redox Reactions15m
- Introduction to Cellular Respiration22m
- Cellular Respiration: Types of Phosphorylation14m
- Cellular Respiration: Glycolysis19m
- Cellular Respiration: Pyruvate Oxidation8m
- Cellular Respiration: Krebs Cycle16m
- Cellular Respiration: Electron Transport Chain14m
- Cellular Respiration: Chemiosmosis7m
- Review of Aerobic Cellular Respiration18m
- Fermentation & Anaerobic Respiration23m
- Gluconeogenesis16m
- Fatty Acid Oxidation20m
- Amino Acid Oxidation17m
- 25. The Urinary System2h 39m
- 26. Fluid and Electrolyte Balance, Acid Base Balance Coming soon
- 27. The Reproductive System2h 5m
- 28. Human Development1h 21m
- 29. Heredity Coming soon
26. Fluid and Electrolyte Balance, Acid Base Balance
Fluid Balance
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