Water Balance Flashcards
Describe water.
-neutral charge (proton=electron)
-electrons asymmetric = polar = one end pos & other neg
-hydrogen bonds
Describe a solution, solute, & solvent.
Solution = substance dissolved in liquid
Solute = dissolved substance
Solvent = liquid
Describe hydrophilic VS hydrophobic.
- Hydrophilic
-dissolve
-water surrounds ions & polar molecules
-attract water thru electrical charge - Hydrophobic
-non polar bonds
-insoluble in water
-hydrocarbons = C-H bonds
Describe ECF & ICF.
*60% body weight is water
-ECF = 20% body weight
>plasma, interstitial fluid, transcellular water (1%)
-ICF = 40% body weight
Describe transcellular water.
-1%
-localized to: lymph, CSF, synovial fluid, aqueous humor, endolymph/perilymph, pleural/pericardial/peritoneal, glomerular filtrate
-doesn’t reflect changes in dehydration & doesnt affect fluid balance
Describe water balance.
*amount of water lost = amount water gained
Intake:
-ingested liquid/food, metabolic water
Loss:
-urine, sweat, lungs (water vapor), GI tract (feces)
EX: increased H2O intake during lactation in cows bc of increased milk production
Describe electrolytes.
-dissociated into ions when dissolved
-able to conduct electricity
-cell metabolism
-osmotic movement of water
-maintain acid base balance (H+)
-maintain membrane & action potentials
Describe the 5 electrolytes.
- Ca
-bone & teeth
-blood cog
-neural transmission
-muscle contraction
-PM & cell to cell junctions
-activate enzymes
-messenger - Cl
-form HCl in stomach
-nerve impulses - Mg
-enzyme activation
-neuromuscular transmission - K
-regulate water & electrolyte
-nerve impulses
-acid base balance - Na
-fluid vol reg
-increase PM permeability
-control water distribution
-acid base balance
-nerve impulse
Describe cations VS anions.
Extracellular cation = Na+, Ca+
Extracellular anion = Cl-, HCO3-
Intracellular cation = K+, Mg+
Intracellular anion = phos, protein
Describe homeostasis & water balance.
-homeostatic mechanisms respond to changes in the ECF
-receptors detect changes in composition/volume = endocrine response
-physiological adjustments regulated by hormones
-hormone-mediated responses affect balance between dietary absorption & urinary excretion of water
Describe concentration differences.
Describe osmolality.
-amount of solute per unit of solvent
-electroneutrality = total number of all cations and anions in body fluids are equal
-tonicity = ability of a solution to initiate water movement between ECF & ICF
Describe what the movement of water is controlled by.
- Hydrostatic pressure = pressure against inside of blood vessel (increase in HP = increase in BP)
- Colloid osmotic pressure (oncotic pressure) =
Proteins in blood that pull fluid back into the capillary
*factors that affect net hydrostatic/oncotic pressure = alter fluid distribution in ECF
*changes in conc of solutes in plasma/interstitial fluid = affect water distribution
Describe the osmolality relationship with the ECF.
- If osmolality of ECF increases (lose water, retain electrolytes) = hypertonic ICF -> water moves from cells to ECF
- If osmolality of ECF decreases (gain water without electrolytes) = hypotonic ICF -> water moves from ECF into cell
What are the 3 hormones that regulate fluid imbalances?
-ADH
-Aldosterone
-ANP
Describe antidiuretic hormone. (ADH)
-osmoreceptors (neurons that secrete ADH) in hypothalamus monitor osmotic conc of ECF
-neurons located in anterior hypothalamus but axons release ADH in in posterior pituitary
-rate of ADH release varies w osmolarity
>higher osmolarity = higher ADH
Describe the effects of ADH.
-water reabsorption by kidneys (urine)
-thirst center = fluid intake
-vasoconstriction at high conc
-increase arterial blood volume
-regulate BP
Describe aldosterone.
-secreted by adrenal cortex
-activated by RAAS
-determines rate of Na absorption in kidneys
-higher aldosterone = more kidneys conserve Na (increase sodium channels absorption)
-secretion of aldosterone not directly influenced by Na but by K+
*increase K+ = increase aldosterone -> kidneys eliminate excess K+ (increase K+ excretion)
Describe atrial natriuretic peptide (ANP).
-released by cardiac muscle due to stretching of atrial wall by high BP
-goal: response to normalize BP & reduce stretching by increasing water elimination & sodium in urine
Describe the ANP in the kidneys & nephron.
Kidneys:
-vasodilation of afferent arteriole of glomerulus -vasoconstriction of efferent arteriole
>increases renal blood flow & glomerular filtration rate
>increased filtration & inhibition of reabsorption = increase in excretion of water & urine volume (DIURESIS)
Nephron:
-collecting duct
-reduce reabsorption of Na
>sodium in filtrate is excreted in urine (NATURESIS)
>inhibits Na/H exchange in proximal tubule & Na/H reabsorption in distal tubule (both enhance Na excretion)
Describe the functions of ANP.
-reduce BP
-increase water loss
-reduce thirst
-block release of ADH
-stimulate peripheral vasodilation
*ANP effect are opposed to Angiotensin II
Describe edema.
*presence of excess fluid in tissue (ECF)
Intracellular =
-hyponatremia (low Na)
-depressed metabolic system of cell
-reduced nutrition of cell (ischemia)
-inflammation
Extracellular =
-leakage from plasma to interstitial space
-lymphedema
-increased capillary pressure
-decreased plasma proteins
-increased capillary permeability
-blockage of lymph return
Describe diabetes.
*kidneys cant concentrate urine normally = lg amount of dilated urine
1. Diabetes insipidus centralis
-lack of ADH synthesis in hypothalamus from posterior pituitary (tumors, brain damage)
2. Diabetes insipidus renalis (nephrogenic)
-ADH produced but can’t act in kidney (kidney disease, toxins)
*polyuria, polydipsia, nocturia
Describe water losses 2 categories.
- Insensible water loss = water loss cant be regulated or measured
-exhaled air
-diffusion from skin (not sweat) - Sensible water loss = volume that can be measured
-sweat
-urine
-feces
