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three basic water principles
- a unified whole
- body water compartments
- particles in the water solution
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summarize a unified whole
all water inside body surrounding cells protected and held by skin
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summarize a body water compartment
- dynamic areas within the body.
- total body water
- total in individual locations in body
- membranes seperate
- water is shifted to where its needed
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summarize particles in water solution
- concentration and distribution of part in water
- determines internal shifts and balance amung compartments
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hemeostasis
bodys state of dynamic balance
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wb cannan studied
homeostasis
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body water supply has 4 characteristics
- acts as solvent
- serves as means of transport
- regulates temp control
- provides lubrication for body
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solvent
water is basic liquid solvent for all chem reactions
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polarity
- interaction bs the pos charged end of one molecule and neg end of another.
- effectively dissolves and ionizes substances
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transport
water circulates thru body to meet the needs of cells
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thermoregulation
temp rises = sweat cools body
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lubricant
lubes moving bd parts eg joints
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women bd water requirements
- 2.7 L
- 19% from food
- 74 oz fluid
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men bd water requirements
- 3.7 L
- 0.7 from food
- 101 oz fluid
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two factors increasing water requirements
- physical activity
- environment temp
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surrounding environment factor
- hot- body sweats
- cold - body shivers
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hypoxia
cold induced diuresis
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activity level factor
- more water is lost in sweat
- more water needed in metabolic demand
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athletes should drink how much
5-7 ml per kg bd wt 4 hrs before
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athletes rehydrate
16-24 oz per lb lost during exercise
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functional losses factor
disease altered, water loss often thru urine
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metabolic needs factor
1000ml water needed for metabolism of every 1000kcal in diet
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infant bd water content
- 70-75% total bd wt
- mostly outside cells, easily lost
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other dietary factors
- additives and meds
- natural diuretic effect
- individuals need monitored
- alcohol and caffeine
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dehydration keys
- excessive loss
- after 2% of normal wt lost
- thirst, ha, decreased urine output, drymouth, dizziness
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advanced dehydration s/s
visual impairment, hypotension, loss of appetite, muscle weakness, kidney failure, seizures
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chronic dehydration
increase resting heart rate, kidney infections, fallstones, constipation, adversely influence cognitive functions
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hypothalamus is
regulatory center for thrist, hunger, bd temp, water balance, and bp
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elderly dehydration concern
- hypothalamus changes occur
- decreased thirst, reduced fluid intake
- pysiological changes
- eg kidneys
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hyponatremia
low serum sodium levels of less than 136 meq/l
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water intoxication
- hyponatremia
- blood volume is diluted
- water moves into intracellular fluid spaces to reestablish equilibrium w na concentration--EDEMA, LUNG CONGESTION, MUSCLE WEAKNESS
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polydipsia
excessive thirst and drinking
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those at risk for hyponatremia are
infants, psychiatric pts w polydipsia, pt taking psychotrpic drugs, prolonged endurance
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normal body water content for adults is
45-75% total bd wt
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men have more water content because
higher ration of muscle to fat mass
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which has more water content
muscle or addipose tissue
muscle
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extracellular fluid
- total amount outside cell
- ecf
- 20% total bd wt
- 34 % total bd water
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remaining 3/4 total bd wt 15%
- water that surrounds and bathes tiss
- water in lymphatic circulation
- water moving thru bd tiss secretions
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what helps w movement of materials in and out of bd cells
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transcellular fluid is the
- smallest component of ecf
- in gi tract, ocular and jnt fluid, urine in bladder
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intrecellular fluid
- total bd water insde cells
- twice amount of % total bd water
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overall water balance
water enters and leaves bd various routes controlled by basic mechanisms
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average adult metabolizes
2.5 - 3 L of water per day
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water enters the body in 3 forms
- liquids consumed
- foods
- product of cell oxidation when nutrients in body are burned for energy
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xerostomia
severe reduction in flow of saliva that negativelty effects food intake
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recommended minimum fluid intake
1500-200 ml per day
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water leaves the bd thru
kidneys, skin, lungs, and feces
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obligatory water loss
water that must be excreted thru urine to eliminate metabolic waste
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average fluid output per day
2400 ml
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two main solutes in bd water
electrolytes and plasma proteins
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electrolytes are
small inorganic substances that can dissaciate or break apart in solution and carry an electrical charge
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electical charged particles
ion
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cations
- carry pos charge
- eg na, k, ca, mg
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anions
- carry neg charge
- cl, becarbonate cho, phosphate po, sulfate so
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constant balance bw electrolytes maintian
electrochemical and cell membrane potentials
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meq represent
number of ionic charges or electrovalent bonds in a solution
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plasma proteins
- albumin and globulin
- are organic compounds of large molecular size
- dont move as freely
- retained in bld vessels
- control water movement and blood v
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colliods
influence shift of water in and out of capillaries in balance w the surrounding water
plasma proteins
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colloidal osmotic pressure
maintian integrity of bld vol
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small organic compounds
- dissolved in bd water
- too small to influence shifts of water
- can be found in large concentration to influence movement
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example of a small organic compound solvent
- glocuse
- can increase water loss leading to polyuria when in high concentrations
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seperating membranes
seperate and contain water thruout bd
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2 types of seperating membranes
capillary membranes, cell membranes
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capillary membranes
- water molecules and small parts can move across thin capillary walls
- electrolytes and nutrient materials flow free
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cell membranes
- specially constructed to protect and nourish cells contents
- molecules and ions use channels within the phospholipid bilayer to pass across membrane
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osmosis
movement of water molecules from an area of low solute to an area w high solute concentraion
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osmotic pressure
when solutions of concentrations exist on either side of selectively permeable membranes this pressure moves water across membrane to help equalize both sides
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diffusion
force by which parts move outward in all directions from an are of greater concentration to an area of lesser
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facilitated diffusion
membrane transporters assist parts w the crossing of the membrane.
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filtration
water is forced or filtered thru small pores of membrane
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active transport
- vital part must move thru bd processes at all tiems
- carries upstream
- helper-carrier ferries
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pinocytosis
- larger molecule attach to outside cell and cell engulfs them
- encased in vacuole
- main way fat in absorbed in sml intestine
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one of bds most important controls in maintaining overall water balance is
capillary fluid shift mechanism
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purpose of cap fluid shift mech
- water and nutrients must get out of bld vess--
- metablolites must get back to cap--
- by means of opposing fluid pressure
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opposing fluid pressures
- 1 hydrostatic pressure- intracapillary bp from contracting heart muscle pushing bld into circ
- 2 cop - pressure from plasma prot draws tiss fluids back into ongoing circ
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process of cap fld shift mech
- greater bp from heart forces water and small parts into tissues to bathe and nourish cells--then cop draw back water and metabolites--
- balanced bw bp and osmotic pressure of plasma proteiin parts
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2 major organ systems that help protect homeostasis of bd water
gi circ and renal circ
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gi circ
all secretions, except bile, are water--latter portions of intestines water is reabsorbed--constant movement maintained isotonicityw surrounding extracellular water-- risk for clinical imbalances
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law of isotonicity
- gi fluids part of ecf capartments, also include blood--
- isotonic state of equal osmotic pressure--
- if you consume only water, electrolytes and salts enter intestine to even out--
- if you consume only food, additional water is drawn into intestine
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most common cause of clinical fluid and electrolyte problems
upper and lower gi losses
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renal circulation
kidneys filter blood, reaborb water and needed nutrients-- laundering of bld by millions of nephrons water balance and proper solution of bld are maintained
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2 hormonal controls to help maintian sonstant bd water balance
- antidiuretic hormone mechanism
- renin-angiotensin-aldosterone system
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antidiuretic hormone mechanism
- vasopressin
- syntehsized by hypothalamus
- stored in pit gland for release
- conserves water
- works on kidneys nephrons to induce reabsorption of water
- stressful situation-released to conserve water
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renin-angiotensin-aldosterone system
- when bld flow to kidneys drop below normal, enzyme renin is released into bld.
- renin converts angiotensinogen to "1, "1 travels to lungs where ace converts to "2- vasoconstriction triggers release of aldosterone from adrenal glands- aldo stim kidneys nephrons to reabsorb na
- SODIUM CONSERVING MECHANISM
- SECONDARY CONTROL OVER WATER REABSORPTION (WATER FOLLOWS NA)
- activated by stress also
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acid base balance
- optimal degree acid/alkin must be maintained
- achieved by chem and physical buffer systems
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concept of acids and bases
- hydrogen ion concentration. pH
- higher hydro ion concentration = lower pH
- lower than 7 acidic
- higher alkaline
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acids
compound that has more h+ and has enough to relase extra when it is in solution
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bases
- compound w fewer h+
- in solution, accepts H+, reducing solutions acidity
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acid base buffer system
bd deals w degrees of acidity by maintaining buffer systems to handle and excess acid or base
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chem buffer system
- mixture of acidic and alkalinine components
- acid and base partner that protect solution from wide variants of pH
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bodys main buffer system is
carbonic acid/becarbonate
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h2co3/nahco3 main reasons
- availability of materials
- base-to-acid ratio
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physiologic buffer system
- resp and renal systems respond
- when chem buffers cannot reestablish equilibrium
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resp control of pH
co2 leaves w breath, changes in resp rate can incr or decr loss of acids
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acidosis
- pH less than 7.35
- accumulation of co2
- significant loss of bicarbonate
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alkalosis
- pH more than 7.45
- resp alk caused by hyperventilation and excess loss of carbon dioxide
- extensive vomitting w hydrochloric acid lost and bicarbonate secreted
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urinary control of pH
- when chem and resp buffers do not reestablish pH, kidneys can adapt by excreting more or less H+
- if blood is too acidic, kidneys will accept more H+ in exchange for na+
- na+ are basic, blood is losing an acid while gaining base- increasing blood ph back to normal
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