Nutrition ch9: Water and Electrolyte Balance

1. How much water should I drink two hours before exercise? 2. Should I worry about dehydration if I lose a small amount of weight after a workout? 3. How much water should I drink after exercise?

1. 5-10 ml/kg of fluid would be appropriate during that time. 2. You won't show symptoms of dehydration until losing more than 1% to 2% of regular body weight 3. You should try to drink 20 to 24 oz for every pound of weight lost.

What are the six things that can alter someone's fluid requirements? Be able to describe each to the level covered in the lecture.

1. Activity level - fluid intake needs during activity are highly variable and depend on: body size, sweat rates, and type of activity 2. surrounding environment - both external climate and internal heat production from physical labor can increase the body temperature and lead to water loss through sweating - water needs are increased with cold temperature and altitude due to greater respiratory water loss, hypoxia or cold induced diuresis and increased energy expenditure 3. functional losses (prolonged vomiting/diarrhea, uncontrolled diabetes mellitus) 4. metabolic needs (1ml fluid needed/1kcal consumed) 5. age (high breast milk or formula critical during infancy due to infants body being 70-75% water) 6. caffeine and medications

Describe the four functions of water.

1. Solvent (Water is basic liquid solvent for all chemical reactions within the body) 2. Transportation (water transports nutrients, secretions, metabolites, and other materials in blood and other tissue fluids) 3. Thermoregulation (water is necessary for maintaining a stable body temperature) 4. Lubricant (water lubricates moving parts in the body, such as joints (synovial fluid) to prevent damage from constant friction

The action of antidiuretic hormone on the kidney causes ________________. A) water excretion B) sodium retention C) water retention D) sodium excretion

C Antidiuretic hormone is a water-conserving mechanism that works on the kidneys' nephrons to induce reabsorption of water. In any stressful situation with threatened or real loss of body water, this hormone is released to conserve vital body water. Page 147.

Be able to explain the steps of each of the two hormonal systems that control water balance in the body (antidiuretic hormone and the renin-angiotensin-aldosterone-system) and the overall purpose of each.

1. antidiuretic hormone (vasopressin) (ADH) - first line defense against hypovolemia - synthesized by the hypothalamus and stored in pituitary gland - conserves water by stimulating kidneys' nephrons to increase the reabsorption of water and by causing vasoconstriction. - restores normal blood volume and osmotic pressure 2. renin-angiotensin-aldosterone-system (RAAS) - purpose is to correct hypovolemia by stimulating the kidneys to reabsorb sodium, which results in great water retention

Describe both how chemical buffer systems work in the body to maintain stable blood pH, as well as both of the types of physiological buffer systems.

1. chemical buffer systems: - when an acid and base join together to withstand variations in body pH - when a strong acid is added to a buffered solution, the base partner reacts with the acid to form a weaker acid - the carbonic acid (H2CO3) bicarbonate (NaHCO3) buffer system is the body's main buffer system. WHY? -> the raw materials are readily available (H2O and CO2) -> able to maintain a ratio of 20:1 (base to acid) regardless of what enters system to maintain acidity needed in body fluids. 2. physiological buffer systems: - when chemical buffers cannot reestablish pH equilibrium the respiratory and renal systems kick in. - respiratory control: -> hyperventilation will increase the release of CO2 (an acid), combating acidosis -> hypoventilation will lead to retention of more CO2 to alleviate alkalosis - Urinary control: -> The kidneys can adapt to pH changes by secreting either more or fewer hydrogen ions -> if blood pH becomes too acidic, the kidneys will accept more hydrogen ions from the blood in exchange for sodium ions (which are more basic)

What are the two particles that control water balance in the body? Be able to describe the role of each type of particle in water balance.

1. electrolytes - inorganic, usually single-mineral elements that carry a charge - in any chemical solution cation electrolytes and anion electrolytes are constantly in balance to maintain electrical neutrality. - water will follow electrolyte charges, and go to the side of the cell membrane that has the greater number of electrolytes. 2. plasma proteins - large organic molecules in blood plasma (mainly albumin and globulin proteins) - too large to easily diffuse across capillary membranes, so they stay inside the blood vessels - albumin proteins (colloids) attract water inside blood vessels using colloidal osmotic pressure to maintain equilibrium of the solute concentration between to fluid compartments - without plasma proteins, fluid leads from capillaries to intracellular spaces and edema occurs.

Why is hydrating with plain water only after prolonged exercise with significant sweating potentially dangerous? (Focus your answer on sodium)

1. possibility of hyponatremia (low serum sodium)- loss of excess sodium 2. water intoxication (can lead to hyponatremia)- the shift of excess water to intracellular fluid to balance sodium concentrations can lead to lung congestion, edema, and muscle weakness

List mild and sever symptoms of dehydration. What percent fluid loss requires medical attention for full recovery?

1. symptoms become apparent after losing 1-2% of normal body weight 2. negative impact on cognitive function, fatigue, and mood levels as low as fluid loss of 1% of body weight 3. fluid loss >10% of body weight typically requires medical attention for complete recovery 4. symptoms range from thirst- stronger thirst, vague discomfort, loss of appetite- decreasing blood volume, impaired physical performance- increased effort for physical work, nausea- difficultly concentrating- failure to regulate excess temperature- dizziness, labored breathing with exercise, increased weakness- muscle spasms, delirium, and wakefulness- inability of decreased blood volume to circulate normally, failing renal function.

What does the pH of a body fluid tell us? What is the blood pH compatible with life?

7.35-7.45 pH compatible with life pH denotes hydrogen ion concentration in fluid acids have extra hydrogen ions, and can therefore release them when in a solution bases have fewer hydrogen ions, and can therefore accept them in a solution

A [blank] is a substance that induces urination and subsequent fluid loss. A) diuretic B) anti-diuretic hormone C) electrolyte D) plasma protein

A

A mineral that occurs in the highest concentration in the intracellular fluid is _________________. A) potassium B) magnesium C) sodium D) phosphorus

A

Body water requirements are increased by ___________________. A) diarrhea and vomiting B) age C) emotional stress D) lower environmental temperature

A

The acid-base physiological buffer system is mainly controlled by the ________________. A) lungs and kidneys B) kidneys and skin C) heart and brain D) lungs and liver

A

________________ stay in the blood vessels and draw water into the vessels to establish equilibrium of the solute concentration between the fluid compartments. A) Plasma proteins B) Iron atoms C) Hydrogen ions D) Proenzymes

A

The cations primarily responsible for controlling body water distribution are ________________. A) sodium and bicarbonate B) calcium and phosphorus C) sodium and potassium D) sodium and chloride

C Sodium and potassium are cations that function to control the distribution of water in the body. Sodium is the major extracellular electrolyte and potassium is the major intracellular electrolyte. Page 143.

The kidneys must excrete water in the urine because _________________. A) water provides the vehicle for excretion of waste products B) they physiologically cannot retain all the water C) the body needs to get rid of the water ingested D) hormones ensure that a maximal amount of water is retained by the body

A The largest amount of water exits through the kidneys. A certain amount of water must be excreted as urine to carry out the various waste products of metabolism. This is called obligatory water loss because it is compulsory for survival and must occur daily for health. The kidneys may put out an additional amount of water depending on body activities and needs, which is referred to as optional water loss. Page 143.

The two minerals that occur in the extracellular fluid and regulate water balance are ________________. A) phosphorus and magnesium B) calcium and potassium C) sodium and chloride D) potassium and magnesium

C

Treatment for diarrhea in children is to ___________________. A) sponge with an electrolyte solution B) administer the BRAT (bananas, rice, applesauce, and tea) diet C) give age-appropriate diet along with oral fluids that contain sodium, potassium, sugar, and sodium bicarbonate D) withhold oral intake until diarrhea stops

C Administering an age-appropriate diet along with fluids that contain sodium, potassium, glucose, and sodium bicarbonate is beneficial in treating diarrhea and replacing lost fluid and electrolytes to bring the body to a state of homeostasis. Page 147, Cultural Applications.

Plasma proteins maintain colloidal osmotic pressure because __________________. A) proteins are positively charged B) proteins are not found in the cells C) they contain water as part of their structure D) they are large molecules

D Plasma proteins maintain colloidal osmotic pressure because they are large molecules, mainly in the form of albumin and globulin. Plasma protein molecules are retained in the blood vessels, controlling water movement in the body and guarding blood volume by influencing the shift of water in and out of capillaries in balance with the surrounding water, which in this form is referred to as colloids. Page 143.

An example of a cation is ________________. A) phosphorus B) sulfate C) carbonate D) glucose E) sodium

E

Water's functions DO NOT include acting as (a) ________________. A) transporter B) solvent C) thermoregulator D) lubricant E) hormones

E Body water functions include serving as a solvent, transport secretions and tissue fluids, assists with thermoregulation, and has a lubricating effect on moving parts of the body. Pages 133-134.

Thirst tends to be an unreliable index of fluid needs particularly in ___________________. A) pregnant women B) breastfeeding women C) infants D) teenagers E) older adults

E Thirst is an unreliable index of fluid needs in the elderly because the thirst mechanism usually diminishes with age and dehydration can easily occur. Page 141

Where is intracellular fluid found in the body? Where is extracellular fluid found? (Know the four types of fluid constituting extracellular fluid discussed on the Body Water Distribution slide)

Intracellular fluid (ICF)= 2/3 total body water extracellular fluid (ECF)=1/3 total body water (1/4 in blood plasma, rest in interstitial fluid, lymphatic fluid, and transcellular fluid)

Be able to describe when you would recommend someone rehydrate with both fluid and electrolytes (sodium and chloride) versus with only plain water

Physically fit athletes can usually maintain hydration with plain water for exercise <90mins ENDURANCE athletes need water, fuel (carbs), and sodium for exercise lasting longer than 60-90 mins, especially in hot weather hyponatremia (low sodium) is rare, but can be fatal. Can happen to endurance athletes who lose excess sodium through sweating and hydrate with plain water only. sports drinks with extra vitamins/minerals do not have evidence of improved performance and could lead to consuming megadose amounts of vitamins and minerals. sports drinks with ingredients such as gingko biloba, taurine, and guarana do not have well established safety and efficacy and the actual amount in a drink may be unknown.

How much fluid do athletes need to hydrate with prior to exercise? What about after exercise?

Prior: 5-10ml/kg of body weight of fluid at least two hours before after: 20-24oz of fluid per each pound of body weight that was lost due to sweating.

True or False? Normal body water content ranges from 45%-75% of total body weight in adults.

True

What blood pH would indicate a state of acidosis? Alkalosis?

acidosis: - blood pH <7.35 (pH <7.0 can be fatal) - common signs/symptoms include: headache and confusion, lethargic, and rapid, shallow breathing. - can be cause by: advanced stage of shock (lactic acidosis), diabetic ketoacidosis, inadequate ventilation (COPD, severe pneumonia, asthma, oversedation), diarrhea, or ileostomy. alkalosis: - blood pH >7.45 (pH >7.8 can be fatal) - common signs/symptoms: tingling/numbness in extremities, nausea/vomiting, cognitive impairment that progresses to unconsciousness - can be caused by: stomach acid lost during periods of prolonged vomiting, prolonged suctioning with stomach tube, and hyperventilation

Describe why older adults are at greater risk for dehydration.

age-associated changes in hypothalamus (thirst sensation) and kidneys, as well as a reduced intake of fluids.

Plasma proteins maintain ________________ osmotic pressure because they are large molecules, mainly in the form of albumin and globulin.

colloidal

What are the symptoms of hyponatremia?

delirium seizures coma death

____________ is a term that refers to excessive thirst and drinking.

polydispsia

What is the purpose of diuretic medications and what are some potential adverse effects of diuretics related to water and electrolyte balance?

rid body of excess fluid and reduce blood pressure Monitoring individuals who are using diuretics for dehydration and electrolyte imbalances is top priority.

What are the average daily water requirements for sedentary men and women?

women: 2.7L (91 oz) from food AND beverages men: 3.7L (125oz) from food AND beverages