Unformatted text preview: Lecture 12: Fluids and Electrolytes Lecture 12: Fluids and Electrolytes
Outline Overview of fluids and electrolytes in the body Distribution of body fluids Roles of body fluids, electrolytes Thirst mechanism Water intake/losses Disorder due to imbalance of body fluids & electrolytes Benefits of eating plant foods Fluids, electrolytes Fluids, electrolytes
Fluids – move freely and change form according to the shape of container Body fluids – water plus dissolved substances (solutes) = liquid portion of cells and tissues some of the solutes are minerals (sodium, potassium, chloride, phosphorus, calcium) which are called electrolytes Electrolytes become dissociated into + and – ions when dissolved in water Our body is mostly water (earth’s surface is 75% water!) Our body is mostly water ( Body fluids and electrolytes Body fluids and electrolytes
Big picture: The body is mostly made of water (~6070% in children, ~5060% in adults) Cells are mostly made of water (>70%): “life occurs under water”= “biological reactions happen in water” Basics of Body Fluids and Electrolytes Body fluid = liquid portion of cells and tissues = water + electrolytes Cells have electrolytes (positively or negatively charged elements called ions) that serve many functions The major ions inside of cells are potassium (K) and chloride (Cl) The major ions outside of cells are sodium (Na) and chloride (Cl) Distribution of body fluids 2/3 body fluid is within the cells = intracellular fluid 1/3 body fluid is outside the cells = extracellular fluid Extracellular fluid in the tissues/organs = interstitial fluid – flows between the cells that make up a particular tissue/organ Extracellular fluid in the liquid portion of the blood or lymph = intravascular fluid Blood is ~1/3 of extracellular fluid Distribution of body fluids Distribution of body fluids Intravascular fluid Body fluids play important roles Body fluids play important roles Fluids dissolve and transport substances water is excellent solvent for amino acids, glucose, vitamins, minerals, medications – transported in the blood stream Fluids account for blood volume – blood volume is amount of fluid in the blood Blood volumes increases blood pressure increases Blood volume decreases blood pressure decreases Kidney plays a central role in regulating blood volume & pressure Fluids maintain body temperature – water has high heat capacity the ability to take in or release heat without significant temp change, our body water protects us from extreme temperatures Sweating cools the body down – heat transported from body to skin surface through blood – water evaporates cooling effect Fluids protect and lubricate tissues – cerebrospinal fluid in brain and spinal column protects against damage, fluid in mucus linings of stomach and intestines facilitate food movement Electrolytes in body fluid play important roles Electrolytes regulate fluid balance Electrolytes in body fluid play important roles Electrolytes enable nerves to respond to stimuli Electrolytes signal muscles to contract Na+ and K+ play critical roles propagating nerve impulses along nerve and muscle cells Ca++ increase flow from extracellular fluid into muscle cell contraction pump out of cell relaxation Common sources of some electrolytes in diet Na K Dill pickle (4 in) 1731 mg Cured ham (3 oz) 1177 Tomato juice (1 cup) 654 Potato (1 med serving) Yogurt (8oz container) Banana (large) Tomato juice (1 cup) Cheddar cheese (3 oz) Lentils (1 cup) 1081 mg 579 554 556 435 mg 356 P Maintaining fluid balance is essential IN We drink and retain fluid when dehydrated OUT Excrete fluid (urinate) when we consume more than we need Thirst mechanism Controlled in hypothalamus of the brain by group of cells called “thirst mechanism” Stimulated by: Increased concentration of salt and other dissolved substances in blood – eating potato chips, crackers, sandwich – salty Reduction in blood volume and blood pressure – sweating, blood loss, vomiting, diarrhea, low fluid intake Dryness in mouth and throat – indicates low amount of fluid in the blood lower production of saliva Thirst mechanism Hypothalamus detects changes stimulates release of antidiuretic hormone (ADH) – Signals kidney to reduce urine flow and return more water to bloodstream Kidney releases angiotensin II constriction of blood vessels retains more water Water is drawn out of salivary glands in mouth to further dilute substances in blood makes mouth & throat dry Thirst mechanism Thirst mechanism not always sufficient People stop drinking when no more thirsty – but fluid intake may not be enough to restore fluid balance Happens during intense exercise in the heat or high humidity Lesson: drink regularly during the day and not wait till you’re thirsty – carry bottled water Balancing water intake/losses Balancing water intake/losses
Intake: beverages foods metabolic water (water from body’s metabolic reactions) Losses: urine, sweat (sensible water loss noticeable by the person) skin evaporation, exhalation (insensible water loss) faeces Balance between the two is important for a healthy fluid level Intake Beverages Fruits 90100%: watermelon, tomato, cantaloupe 6089%: apple, peach, banana, pineapple, grapes Dried grapes = raisins (119% water) 90100% water: water, tea, coffee, cola, clear broth 6089% water: fruit juices, 2% milk How much water do we need? Depends on age, body size, health status, physical activity, environmental conditions DRI Adult men 1950 yrs old 3.7 L (3.0 L water, ~0.6 L from beverages & foods Adult women 1950 yrs old 2.7 L(2.2 L water, ~0.5 L from beverages & food Water intake & loss: woman expending 2500kcal/day Water intake & loss: woman expending 2500kcal/day Drinking water Carbonated – natural or added CO2 Mineral – contains 250500 ppm of minerals Distilled – all dissolved minerals are removed Purified all dissolved minerals and contaminants are removed Bottled – comes from different sources Rapid popularity in last 20 yrs – 3B gallons of bottled water/yr in US Traveling in another country/ unsure of water source – drink bottled water Disorders due to fluid & electrolyte imbalance Dehydration – fluid excretion > fluid intake Disorders due to fluid & electrolyte imbalance Heat stroke – potentially fatal response to high temp where heat regulating mechanism of the body fails Symptoms: rapid pulse, hotdry skin, high temperature, dizziness, loss of consciousness Could happen during intense physical activity under high heat and high humidity Disorders due to fluid & electrolyte imbalance Water intoxication Can occur but rare Kidney disease where too much water is retained overhydration and hyponatremia (low Na+ levels) Excessive amounts of water forced on students during fraternity hazing rituals Lesson: anything taken in excess can be toxic Disorders due to fluid & electrolyte imbalance Hypertension – blood pressure > 140/90 mm Hg (systolic/diastolic) 9095% of cases – called primary or essential hypertension – causes unknown – may be due to salt sensitivity Other 5% due to kidney disease, apnea (sleep disorder affecting breathing), chronic alcohol abuse Incidence of hypertension increases with age Reducing hypertension Lose weight – decrease of 67 points for every 17 lbs lost Increase physical activity – easily achievable for most people – light intensity exercise 3060 min or intense exercise for 20 – 30 min Reduce alcohol intake – abstain or no more than 2 drinks/day Reduce salt intake – AI (Allowable Intake) for Na+ 1500 mg/day, do not exceed 2500 mg/day Eat whole grains, fruits, vegetables, low fat protein sources Health benefits Benefits of eating Plant Foods Ecological benefits Diets high in plant foods correlate with low incidence of cancer Vegetarian women have lower incidence of osteoporosis Soy reduces the risk of cardiovascular disease (lower total cholesterol, lower LDL cholesterol, lower triglycerides) Ecological benefits Increased land productivity Use of water to produce food Productivity of land ...
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- Spring '08
- 175, Extracellular fluid, electrolytes Body fluids