EXAM III REVIEW 1 Describe the average fluid distribution functions of water relative tissue content and daily water balance both under normal and exercise conditions a Water is 50 60 of body weight 40L b Functions of water Intracellular fluid is 20 of body weight 25L i ii Extracellular fluid is 40 of body weight 15L Interstitial fluid is 80 of ECF 12L 1 2 Plasma is 20 of ECF 3L i Transport nutrients and waste products ii Regulate body temp with exercise iii Participate in biochemical reactions iv Protection lubrication cleansing cushioning v Solvent in the body c Body water content of tissues the higher the water content the faster the electrical impulse gets there d i ii iii Body iv TBW Water Weight v ix 2 55 Exercise often increases the percentage of water distributed Adipose vi Muscle x 10 vii 76 xi viii xii 12 43 within the intracellular compartments from increase muscle mass and its large Water content Acute bouts of exercise shifts fluids from plasma to interstitial and intracellular spaces by increasing hydrostatic pressure 2 Know what thermoregulation is and how the body defends against being too hot or cold a Thermoregulation is the ability of an organism to keep its body temperature within a certain boundary even when the surrounding temperature is different b The hypothalamus is the central coordinating center for temperature regulation i Maintains 37 degrees Celsius ii iii Becomes activated in 2 ways Initiates response to protect body from heat gain loss 1 Temperature change in blood perfusing the hypothalamus directly stimulates the thermoregulatory control center 2 Thermal receptors in the skin provide input to modulate hypothalamic activity iv Skin subcutaneous tissues help regulate temperature v Heat defense 1 Radiation a Body Air Sold cooler objects around us b The body absorbs radiant heat energy when the temperature of objects in the environment exceeds skin temperature 2 Conduction 3 Convection a Transfers heat directly through a liquid solid or gas from one molecule to another b Transfers most of body heat to shell a Little or no air movement warmed air next to the skin acts as a zone of insulation minimizing further conductive heat loss a Provides major physiological defense against 4 Evaporation vi Considerations overheating 1 Ambient temperature Sweat rate increases directly with ambient temperature 2 Humidity percent of water in ambient air at a particular temperature compared with the total quantity of moisture that the air could carry a High humidity useless water loss through evaporation 3 Exercise intensity a Heat generated by active muscles can raise core temperature to fever levels that incapacitate a person if caused by external heat stress alone 4 Surface exposure a Athletes with less surface exposure football players hockey players are more prone to getting hot quicker b Because they have less evaporation and evaporation of sweat cools you down 5 Convective air currents around the body vii Circulatory system is the workhorse to maintain thermal balance 1 At rest and in hot weather HR increases and blood flow increases and arterial and venous blood vessels dilate to send blood to body shell reddening of face viii ADH increases water reabsorption posterior pituitary gland ix Aldosterone from the adrenal cortex increases Sodium reabsorption 1 With sodium comes water 3 Know the body content functions daily intake and concentrations of electrolytes discussed in class a Sodium i 65g ii Control of extracellular fluid volume regulation of osmolality acid base balance cell membrane resting potential active transport across cell membranes 1 Sustains thirst drive 2 Retain ingested fluids 3 Restore plasma volume iii Average daily intake 1 8 5g d iv The more sodium you have less urine output you have v Concentration 140 in plasma 9 in the cells More sodium outside the cells b Potassium i 180g ii Minor amounts lost in sweat Control of intracellular fluid volume Regulation of osmolality acid base balance cell membrane potential iii Daily intake in men 2 945 mg d iv Daily intake in women 1 976 mg d v Best food sources citrus fruits bananas orange juice vi Concentration 4 in plasma 162 in the cells potassium is tomato juice higher inside the cell 4 Identify which factors regulate fluid balance Describe how each factor influences fluid balance Which is primary hormone response long term response etc a All of these influence neural and hormonal pathways 1 More fluid intake for warm environment increased 2 Men have higher sweat rates than women varies by i Thirst mechanism sweat loss individual ii Plasma ecf osmolality 1 Aldosterone increases plasma blood volume promotes sodium reabsorption promotes water conservation a Increases blood pressure 2 ADH increases plasma blood volume promotes water conservation released by sweating profusely iii Blood volume pressure 5 Describe physiologically how dehydration affects fluid balance in the different compartments osmolality sweating and performance at varying levels of hypohydration Are there any differences between men and women a Fluid loss will eventually impede heat dissipation reduce heat tolerance and compromise CV function and exercise capacity b 3 dehydration slows gastric emptying and may induce cramps and nausea c For each liter of sweat loss dehydration exercise HR increases 8bpm and Q decreases 1 0 L min d Different sweat rates for an individual men have higher sweat rates e You sweat more in hot humid environment and less in cool dry than women environments 6 What are the ACSM guidelines for exercise and fluid replacement a Prehydration drink 4 hours before exercise b During exercise Develop customized fluid replacement which prevents 2 dehydration c Post exercise consuming beverages and meals will expedite rapid and complete recovery by stimulating thirst and fluid retention d Drink at least 125 150 of the existing fluid loss as soon as possible after exercising water lost in urine i The 25 50 extra water accounts for that portion of ingested e A small amount of potassium enhances water retention in the intracellular space and may diminish any extra potassium loss that results from sodium retention by the kidneys f Unless the beverage has a sufficiently high sodium content excess fluid intake merely increases urine output with no benefit to rehydration g Drink 3 cups of fluid per lb of wt lost during activity 7 Know the characteristics of the various heat exercise related illnesses discussed in class a