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Chapter 9 Lecture Chapter 9: Nutrients Involved in Fluid and Electrolyte Balance © 2017 Pearson Education, Inc. Body Fluids • Body fluid is the liquid portion of cells and tissues • Characterized by its ability to move freely and changeably, adapting to the shape of the container that holds it • About 50–70% of healthy adult body weight © 2017 Pearson Education, Inc. Body Fluids • Intracelluar fluid: within the cell • 2/3 of body fluid • Extracellular fluid: outside the cell • 1/3 of body fluid • Interstitial fluid flows between cells that make up a particular tissue or organ (muscle, liver) • Intravascular fluid is the water in the blood and lymph • Plasma transports blood cells within arteries, veins, and capillaries © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Body Fluids • Fluid composition of tissue varies by: • Tissue type: lean tissues have higher fluid content than fat tissues • Gender: males have more lean tissue and therefore more body fluid than females • Age: decrease in body water results partly from loss of lean tissue as people age © 2017 Pearson Education, Inc. Electrolytes • Electrolytes are dissolved substances that disassociate in solution into electrically charged particles called ions • Positive charge (cations): sodium, potassium • Negative charge (anions): chloride, phosphorus • Predominant electrolytes • Extracellular fluid: sodium, chloride • Intracellular fluid: potassium, phosphorus © 2017 Pearson Education, Inc. Functions of Body Fluids • Fluids dissolve and transport substances • Water is an excellent solvent because it dissolves a variety of substances • Water-soluble substances are readily transported in the bloodstream: amino acids, glucose, water-soluble vitamins, minerals, some medications • Fatty substances must be attached to or surrounded by water-soluble proteins © 2017 Pearson Education, Inc. Functions of Body Fluids • Fluids account for blood volume • Appropriate body fluid levels are essential for maintaining healthful blood volume • Blood pressure increases when blood volume rises • High blood pressure (hypertension) is a risk factor for heart disease and stroke • Low blood pressure can cause people to feel tired, confused, or dizzy • Kidneys help to regulate blood volume and blood pressure © 2017 Pearson Education, Inc. Functions of Body Fluids • Fluids account for blood volume • Antidiuretic hormone (ADH) released from the pituitary gland stimulates the kidneys to reabsorb water, reducing urine output • Enzyme renin secreted from the kidneys responds to decreased blood pressure; catalyzes the conversion of blood protein angiotensinogen to angiotensinogen I © 2017 Pearson Education, Inc. Functions of Body Fluids • Fluids account for blood volume • Angiotensin I is converted to Angiotensin II (vasoconstrictor); increases blood pressure • Hormone aldosterone secreted from the adrenal glands signals the kidneys to retain sodium and chloride, thereby retaining water, increasing blood pressure, and decreasing urine output © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Functions of Body Fluids • Fluids help maintain body temperature • Fluids maintain body temperature within a safe range • Water has a high capacity for heat, which means that only sustained high heat can increase body temperature • Sweating releases heat as the evaporation of water from the skin cools the skin and blood © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Functions of Body Fluids • Protect and lubricate tissues • Cerebrospinal fluid protects the brain and spinal cord • Amniotic fluid protects the fetus • Synovial fluid lubricates joints • Tears cleanse and lubricate eyes • Saliva moistens food for swallowing • Pleural fluid allows lungs to expand and retract without friction © 2017 Pearson Education, Inc. Functions of Electrolytes • Electrolytes help regulate fluid balance • Cell membranes are permeable to water, but not freely permeable to electrolytes • Water moves by osmosis to areas where the concentration of solute is high • This action provides a means to control movement of water into and out of the cells • Osmotic pressure keeps electrolytes in solution from drawing liquid toward them across a semipermeable membrane © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Functions of Electrolytes • Electrolytes enable nerves to respond to stimuli • Nerve impulses are initiated at nerve cell membranes in response to a change in electrical charge across the membrane • Depolarization—Action Potential— Repolarization • Sodium and potassium ensure that nerve impulses are generated, transmitted, and completed © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Functions of Electrolytes • Electrolytes signal muscles to contract • Muscles are stimulated to contract in response to stimulation of nerve cells • Increased flow of calcium ions from its storage site into the muscle stimulates muscle contraction • Muscles can relax after contraction once the electrical signal is complete and calcium is pumped out of the muscle cell © 2017 Pearson Education, Inc. Fluid Balance • Fluids gained through consumption and metabolism • As much as 90% of fluids needs met by beverages and food • Metabolic water formed from metabolic reactions contributes 10–14% of the water the body needs each day © 2017 Pearson Education, Inc. Fluid Balance • Thirst mechanism (hypothalamus) prompts us to drink. It is stimulated by: • Increased concentration of salt and other dissolved substances in the blood • A reduction in blood volume and blood pressure, such as during profuse sweating, vomiting, diarrhea, or low fluid intake • Dry mouth and throat from reduced saliva • ADH signals the kidneys to retain water © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Fluid Balance • Sensible fluid loss • Kidneys excrete water as urine • Sweat during exercise or in hot environment • Insensible fluid loss • Skin (not sweating) or lungs during exhalation • Significant loss • Illness, traumatic injury, blood donation, surgery, exercise, high altitude, low humidity, pregnancy, breastfeeding, diuretics © 2017 Pearson Education, Inc. How Much Water Should We Drink? • Requirements are individualized • Amount needed varies with age, body size, health status, physical activity level, environment • Athletes, highly active people, and people working in hot environments may need additional fluid to replace fluid lost in sweat • Sources of drinking water: tap, carbonated, mineral, bottled • Distilled and purified water not suitable for drinking © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Minerals Contribute to Fluid Balance • Major extracellular cation • Functions of sodium: • Allows cells to maintain fluid balance • Blood pressure regulation • Transmission of nerve signals • Muscle contraction and relaxation • Assists in glucose absorption from the small intestine © 2017 Pearson Education, Inc. Sodium • How much sodium? • AI: 1.5 g/d; other health groups recommend no more than 2.3 or 2.4 mg/d • Found naturally in many foods, processed and restaurant foods are high in sodium • High sodium diets associated with high blood pressure © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Sodium (cont.) • What if you consume too much sodium? • Hypernatremia is abnormally high blood sodium concentration • Patients with congestive heart failure or kidney disease cannot effectively excrete sodium • Causes high blood volume, edema (swelling), and high blood pressure © 2017 Pearson Education, Inc. Sodium (cont.) • What if you don't consume enough sodium? • Hyponatremia is abnormally low blood sodium level • From prolonged sweating, vomiting, diarrhea • Symptoms: headaches, dizziness, fatigue, nausea, vomiting, and muscle cramps • If untreated: seizures, coma, and death © 2017 Pearson Education, Inc. Potassium • Major intracellular cation • Together with sodium, maintains fluid balance, regulates transmission of nerve impulses, and muscle contraction • High potassium intake helps maintain a lower blood pressure • How much potassium? • Recommended intake is 4.7 g/day © 2017 Pearson Education, Inc. Potassium (cont.) • Sources of potassium • Good sources include: fresh fruits, vegetables, legumes, and whole grains • Processing foods increases sodium and decreases potassium content © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Potassium (cont.) • What happens if you consume too much potassium? • Hyperkalemia: high blood potassium levels • Can alter normal heart rhythm, resulting in heart attack and death • People with kidney disease are unable to regulate their blood potassium levels and should avoid consuming potassiumcontaining salt substitutes © 2017 Pearson Education, Inc. Potassium (cont.) • What happens if you don't consume enough potassium? • Hypokalemia: low blood potassium levels • Seen in people with kidney disease or diabetic ketoacidosis • Can occur when taking certain diuretics and with extreme dehydration, vomiting, diarrhea, alcohol abuse, long-term consumption of natural licorice (glycyrrhizic acid or GZA), or eating disorder (abnormal heart rhythms) © 2017 Pearson Education, Inc. Chloride • Major extracellular anion • Functions of chloride • Assists with fluid balance • Aids digestion: hydrochloric acid (HCl) in the stomach • Assists the immune system • Transmission of nerve impulses • Recommended intake • AI: 2.3 g/day © 2017 Pearson Education, Inc. Chloride (cont.) • What happens if you consume too much chloride? • Primary dietary source: table salt • Hypertension in salt-sensitive individuals • What happens if you don't consume enough chloride? • This is rare but can occur in people with severe dehydration, frequent vomiting, and eating disorders © 2017 Pearson Education, Inc. Phosphorus (cont.) • Major intracellular anion • Functions of phosphorus: • Fluid balance maintenance • Critical role in bone formation • Regulates biochemical reactions by activating or deactivating enzymes (phosphorylation) • Found in ATP, DNA, RNA, cell membranes (phospholipids), and lipoproteins © 2017 Pearson Education, Inc. Phosphorus (cont.) • Recommended intake • RDA for phosphorus is 700 mg/day • Sources of phosphorus • Widespread in many foods • High in protein foods (meat, milk, eggs) • More readily absorbed from animal sources • Phytic acid: plant storage form (beans, whole grains, nuts) • Soft drinks © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Phosphorus (cont.) • What happens if you consume too much phosphorus? • High blood phosphorus can occur among people with kidney disease or when taking too many vitamin D supplements • Causes muscle spasms, convulsions • What if you don't consume enough phosphorus? • Deficiencies of phosphorus are rare © 2017 Pearson Education, Inc. Disorders Related To Fluid And Electrolyte Imbalance • • • • • • • • Dehydration Heat stroke Water intoxication Hypertension Neuromuscular disorders Kidney disorders Congestive heart failure Obesity © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Dehydration • Dehydration occurs when fluid loss exceeds fluid intake • Commonly due to heavy exercise or high environmental temperatures • Elderly and infants are at increased risk © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Heat Stroke • Heat stroke occurs from failure in the body's heat-regulating mechanisms • Hot, humid environments • Symptoms: rapid pulse, hot and dry skin, high body temperature, loss of consciousness • Fatal during exercise in extreme heat • Stop exercising when feeling dizzy, lightheaded, disoriented, or nauseated © 2017 Pearson Education, Inc. Water Intoxication • Overhydration (water intoxication) can occur, but it is rare • Kidneys retain too much water, causing overhydration and hyponatremia • Documented cases of deaths among college students (hazing rituals) © 2017 Pearson Education, Inc. Hypertension • Hypertension: major chronic disease characterized by high blood pressure • Often without symptoms • Increases a person's risk of heart disease, stroke, kidney disease • Can reduce brain function, impair physical mobility, and cause death • Systolic pressure over 140 mm Hg • Diastolic pressure over 90 mm Hg © 2017 Pearson Education, Inc. Hypertension (cont.) • What causes hypertension? • Primary (or essential) hypertension: unknown cause for 90–95% of cases • 5–10% of cases are caused by kidney disease, sleep apnea, and chronic alcohol abuse • Salt sensitivity: about 2/3 adults with hypertension © 2017 Pearson Education, Inc. Hypertension (cont.) • Recommendations for reducing hypertension: • Losing weight • Regular exercise • Limiting alcohol intake • Reducing sodium intake • Eating more whole grains, fruits, vegetables, and low-fat dairy foods • DASH diet • Avoid tobacco products © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Hypertension (cont.) • Medications • Help in normalizing blood pressure • Should also continue to practice healthful lifestyle changes • Hypertension: "the silent killer" • Often no obvious symptoms of this disease • Importance of regular blood pressure check © 2017 Pearson Education, Inc. Neuromuscular Disorders • Electrolyte imbalances can alter nervous system and muscle function • Seizures: uncontrollable muscle spasms • Muscle cramps: involuntary, spasmodic, and painful muscle contractions © 2017 Pearson Education, Inc. Kidney and Heart-Related Disorders • Kidney disorders • Kidneys have major role in regulation of fluid, electrolyte, and acid-base balance • Kidney disease can lead to edema and fluid retention • Congestive heart failure • Heart can no longer pump adequate supply of blood throughout the body • Heart can fail on the left or right sides, with varying consequences © 2017 Pearson Education, Inc. Obesity • Popularity of sweetened beverages (U.S.) • 20% of calories from beverages: sweetened soft drinks, fruit juices, sweetened bottled waters, energy drinkds, bottled teas, specialty coffee • Appetite not curbed: extra calories from drinks are not compensated for by eating less • Displace more nutritious beverages such as milk (source of protein, calcium, vitamin D, and other nutrients important for bone health) © 2017 Pearson Education, Inc.