Chapter 8 Water and Electrolytes Water and Water Balance Describe how the elements of a water molecule allow other particles to dissolve in water so effectively Water consists of two hydrogen atoms and one oxygen atom bonded together o The bonding causes a shift in charge among the individual atoms Hydrogen side slightly Oxygen side slightly Allows water to attract other water molecules Other substances that are also charged can dissolve in it Water and Water Balance List the body compartments that water is found in and describe the distribution of water within these compartment Within the body water is found in two major compartments o Intracellular Inside the cells 60 percent of body water o Extracellular Outside the cells 40 of body water Includes Interstitial fluid water surrounding the cells in between Intravascular fluid in veins and arteries Water Balance Water balance o Water intake vs water loss List sources of water intake and water losses Intake includes o Beverages milk juices does not include alcoholic beverages o Foods o Metabolic water Water that is produced during the breakdown of carbohydrate fats and proteins Provides 1 to 1 cups of water per day Losses o Urine o Feces o Insensible losses hard to quantify on a daily basis Sweating Evaporative from expiration breathing Water Balance Fluctuations of water in body common Water has no storage mechanism therefore o Losses must be replaced from consumption of water o Water is essential Must be consumed every day to function on an appropriate level List and describe a critical function of water discussed in lecture One critical function of water in the body o Body temperature regulation Water within the body absorbs this heat Carries it to the skin where it is released as sweat Hydration Water Intake and Retention Describe how water intake and retention is regulated in the body including naming the hormones involved in this function A region of the brain called the hypothalamus controls the body s perceived need for water o Also known as thirst body s perceived need for water thirst mechanism Hypothalamus monitors the body s fluid sodium concentration Triggers thirst when o Water levels in blood is low and solute concentration is high o Therefore thirst lags behind the time when more water is needed The body produces two hormones to help maintain hydration o One is released by the pituitary gland in the brain to signal the kidneys to retain water Antidiuretic hormone body reabsorbs water holds water back into the body The other produced by the adrenal glands above the kidneys it induces the kidneys to retain more sodium and water o Aldosterone hormone involved with fluid regulation in the body Hydration Water Intake and Retention General recommendations for water consumption for adults o 1 1 5 mL kcal of energy expenditure o 8 12 cups of water per day total including beverages and the water contained in food Some people need more or less than this depending on disease state or level of activity Identify risk factors for developing hyponatremia If excess water consumed rapidly or if water and sodium last via sweating and replaced with water only o Water intoxication o Results in dilution of blood electrolytes particularly sodium o Also known as hyponatremia sodium replaced with water Can occur when drinking water rapidly The Dangers of Dehydration Identify risk factors for developing dehydration Dehydration can occur from o Excessive loss through sweating without adequate fluid replacement o Ex Causes vomiting and diarrhea excessive gastrointestinal losses Even mild or early dehydration can result in significant changes in how your body works o Mild dehydration thirst some lack of mental concentration and mild fatigue o Moderate dehydration reduced athletic ability o Severe dehydration cramping and heat exhaustion can result If continue to loose body water hallucinations and heatstroke The Role of Kidneys and Urine in Water Balance Identify the organ responsible for water and waste elimination in the body Water loss primarily via urine Also the primary path for excretion of metabolic waste and the regulation of extracellular fluid composition o The kidneys has microscopic structures that are responsible for filtering blood called Nephron About 1 million in each kidney List the components of urine discussed in class Composition of urine o Water o Electrolytes could be lost in urine o Urea nitrogen o Creatinine Figure 8 3 Nephron of the Kidney CLICKER Which of the following statements regarding water balance in the body is correct 60 of total body water is in the veins and arteries Antidiuretic hormone induces the kidneys to retain sodium only retains water The functional unit of the kidney is the nephron Hypotremia may occur when someone consumes excess sodium and fluid consume excess water and not enough sodium Electrolytes Sodium Potassium and Chloride Definition of Electrolytes o Minerals that when placed in water become charged particles Cations minerals with a positive charge Anions minerals with a negative charge Sodium potassium and chloride are most recognized electrolytes important water balance o Sodium NA primary cation found in the extracellular fluid o Potassium K primary intracellular cation o Chloride Cl an anion more concentrated in the extracellular fluid Dietary Sodium Health professionals universally advise moderating our salt intake Most people who are trying to reduce sodium intake cut back on the salt they add to their food however Identify foods that are high in sodium Main dietary source of sodium from processed foods o 50 75 of sodium intake Added to foods by manufacturers for taste or as a preservative Very little from naturally occurring sodium o 10 less processed foods Dietary Chloride List the AI for sodium for those 50 years and younger and for those over 70 years of age Adequate Intake AI for Sodium o 1500 mg per day for people 50 years old or less o 1200 mg per day for those 70 years and older o KNOW AI for sodium o As with sodium the natural chloride content of most foods is low o Sodium chloride or table salt is approximately 60 chloride Dietary Potassium List the AI for potassium and identify foods that are good sources of potassium o The AI for potassium is 4700 mg per day o Most Americans eat less than this o KNOW AI for potassium o Unlike sodium and chloride potassium is not routinely added to foods o Rich sources of potassium o Fresh fruits and vegetables high in potassium o