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76 Cards in this Set
- Front
- Back
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what is fluid balance and what's involved in it? |
- when the amount of H2O you gain ea day is equal to the amount you lose to the environment. It requires regulating the content and distribution of body water in ECF and ICF. |
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what is electrolyte balance and how is it achieved? |
- the gains and losses of every electrolyte are in balance. It involves balancing absorptive rates across the digestive tract c rates of loss by the kidneys, and secondarily through sweat glands and other sites. |
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what are electrolytes? |
- ions released when inorganic compounds dissociate. |
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what is acid-base balance and how is it achieved? |
- it's when the production of H+ in your body is precisely offset by their loss. The kidneys play a major role in this by secreting H+ into the urine and generating buffers. This occurs largely in the distal segments of the DCT and along the collecting system. The lungs also have an affect by eliminating CO2. |
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so what are the three interrelated processes essential to stabilizing body fluid volumes? |
- fluid balance, electrolyte balance, and acid-base balance. |
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what is ECF composed of? |
- extracellular fluid is the interstitial fluid, plasma, and other body fluids. |
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what is ICF composed of? |
- intracellular fluid is the cytosol. |
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where does the majority of our body's water lie, and what portion, clinically speaking? |
- 2/3 in ICF. |
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where does the majority of water exchange occur among the divisions of the ECF? |
- across the endothelial lining of caps. |
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why are the ECF and ICF called fluid compartments? |
- because they commonly behave as separate sections. |
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which of the fluid compartments' compositions is monitored for homeostatic purposes? |
- the ECF. |
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no receptors directly monitor fluid or electrolyte balance, instead they DO monitor what? |
- plasma volume and osmotic [ ]. |
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what accounts for the movement of water across membranes since cells cannot move water by active trx? |
- osmosis, duh! |
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how do the body's content of water and -lytes change in response to the the body's ingestion and excretion of the same? |
- an increase in water or -lytes, above what the body secretes, will lead to a rise in that component. Likewise for the excessive loss of either. |
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what hormones mediate physiological control of our fluid and -lyte balances? |
1) ADH 2) aldosterone 3) natriuretic peptides |
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how does ADH help adjust fluid-electrolyte balance? |
- the osmoreceptors of the hypothalamus are highly sensitive to changes in the osmotic [ ] of the ECF. These include neurons that secrete ADH, such that the rate of ADH release is directly related to the osmotic [ ]. Higher [ ] = incr ADH secretion and vice versa. |
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what does ADH offer in terms of fluid-electrolyte balance? |
1) causes water resorption at the kidneys, decr water loss through urine and incr urine [ ]. 2) it stimulates the hypothalamic thirst center, promoting fluid intake. |
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how does aldosterone help adjust fluid-electrolyte imbalance? |
- it's secreted in response to incr [K+] or decr [Na+] in the blood reaching the adrenal cortex, or in response to the renin-angiotensin-aldosterone system. |
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what does aldosterone offer in terms of fluid-electrolyte balance? |
- its plasma [ ] helps determine the Na+ retention and K+ loss along the distal portion of the DCT and collecting ducts, thereby altering fluid retention. It also increases the sensitivity of our salt receptors on the tongue, causing an incr desire for salty foods. |
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what 3 things trigger the release of renin from the kidneys? |
1) decr in plasma vol or BP at the juxtaglomerular complex of the nephron. 2) decr in osmotic [ ] of tubular fluid at the DCT. 3) decr [Na+] or incr [K+] in the renal circulation. |
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how do natriuretic peptides influence fluid-electrolyte balance? |
- the atria and ventricles release their ANP and BNP, respectively, in response to incr BP or blood vol stimulating their stretch receptors. |
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how do A/BNP help regulate fluid-electrolyte balance? |
- they block the release of ADH and aldosterone and reduce thirst, thereby reducing water and salt conservation. |
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what component of the ECF contains the most water, and how much is that? |
- the interstitial fluid and the minor fluid compartments. 80%. |
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what is edema?
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- the movement of abnormal amounts of fluid from the plasma to the interstitial fluid. |
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what can cause edema? |
- incr in BP in capillaries, decr in BCOP, damage to capillary walls, constriction of regional venous circulation, or a blockage of the lymphatic drainage. |
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what is metabolic generation? |
- the water produced by our body's cells, primarily as a result of oxidative phosphorylation in mitochondria. |
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what is a fluid shift? |
- a rapid water movement between the ECF and ICF in response to osmotic gradient. |
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what is a hypertonic solution? |
- one c an increased [solute]. |
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what is a hypotonic solution? |
- one c a decreased [solute]. |
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which component holds the majority of our body's water (ICF or ECF), and what does that compartment act as, as a result? |
- the ICF holds far more fluid than the ECF and is therefore able to act as a water reservoir. |
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what is dehydration? |
- develops when water loss outpace water gains. |
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what is hyperhydration? |
- ECF and ICF water volume is too high, resulting in changing [solute] in the ICF, leading to the disruption of normal cellular fxns. |
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what can cause hyperhydration? |
1) drinkning a large vol of water or the infusion of a hypotonic solution. 2) inability to eliminate excess water in urine, dur to chronic renal failure, heart failure, cirrhosis, or some other disorder. 3) endocrine disorders, such as excessive ADH production. |
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what is the majority of ECF osmotic [ ] driven by? |
- sodium salts (NaCl and NaHCO3). |
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what is an Eq (equivalent)? |
- the amount of pos or neg ion that supplies one mole of electrical charge, and 1Eq=1000mEq (milliequivalents). |
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give the two general rules that are particularly worth noting, in regards to sodium balance and potassium balance. |
1) the most common problems c electrolyte balance are caused by an imbalance between gains and losses of sodium ions. 2) problems c potassium balance are less common but significantly more dangerous than those related to sodium. |
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what does not cause [Na+] abnormalities, and what does cause them? |
- Na+ content of the diet does not cause [ ] issues because water follows sodium. Only in severe problems c fluid balance, as in dehydration or overhydration, do sodium [ ] abnormalities occur. |
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how is the [K+] of ECF regulated? |
- by adjusting the rate of active secretion along the distal convoluted tubule and collecting system of then nephron. |
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what factors affect the rate of tubular secretion of K+? |
1) changes in [K+ ] of the ECF. 2) changes in pH affect rate of H+ secretion in place of K+. 3) aldosterone levels: high [K+] stimulate aldosterone secretion directly as does blood volume which stimulates angiotensin 2. |
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what is hypokalemia and what happens in its severe cases? |
- a condition of deficient blood K+ levels. Can cause extensive m. weakness and potentially death due to its effects on the heart. |
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what is hyperkalemia and what happens in its severe cases? |
- a condition of elevated blood K+ levels. Can cause cardiac arrhythmias. |
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what is the most abundant mineral in the body? |
calcium |
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what hormones effect Ca+2 homeostasis and how? |
PTH and calcitriol help incr [Ca+] by incr Ca+ absorption along the digestive tract and along the distal portion of the DCT. Calcitonin helps decr [Ca+]. |
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what is hypercalcemia and what causes it? |
- when the [Ca+2] of ECF exceeds 5.3mEq/L, primarily caused by hyperparathyroidism, which is an over secretion of PTH. |
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what is hypocalcemia and what causes it? |
- when the [Ca+2] of ECF is under 4.3mEq/L (much less common than hypercalcemia), typically caused by hypoparathyroidism, vit. D deficiency, or chronic renal failure. |
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what does Mg+2 do for the body and where is it largely stored? |
- it's an important cofactor for several important enzymatic rxns, including the phosphorylation of glucose within cells and the use of ATP by contracting m. fibers. |
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where is Mg+2 resorbed? |
- the PCT. |
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what does PO4(-3) do for the body and where is it resorbed? |
- it's required for bone mineralization, but as for ICF, the ions are required for the formation of high-energy compounds, the activation of enzymes, and the synthesis of nucleic acids. It's resorbed along the PCT and calcitriol stimulates its resorption. |
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what are the most abundant anions in the ECF and how are they resorbed? |
Cl- is resorbed by carrier proteins that resorb Cl- along c Na+. It's also absorbed along the digestive tract along c Na+. |
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why is the Pco2 the most important factor affecting bodily pH? |
- in the presence of H2O, CO2 spontaneously forms carbonic acid in the blood and even more so in the presence of the carbonic anhydrase in the cytoplasm of RBCs. This then forms HCO3- and H+. So the blood's Pco2 is inversely proportional to its pH. |
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what are buffers? |
- they include weak acids that can donate H+, and weak bases that can absorb H+, and in these ways, help maintain body fluids temporarily. |
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what does a buffer system consist of? |
- generally a combination of a weak acid and the anion release by its dissociation. The anion fxns as a weak base. |
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how does the buffer system work? |
- molecules of the weak acid exist in equilibrium c its dissociation products. Adding H+ to the solution upsets the equilibrium. As a result, additional molecules of the weak acid form, removing some of the H+ from the solution. |
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how does the phosphate buffer system work? |
- consisting of the anion H2PO4- (a weak acid), dissociation creates the anion HPO4(-2). |
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where and how does the phosphate buffer system work best and why not elsewhere? |
- the HPO4(-2) that results from the H2PO4- dissociation is far outnumbered by the HCO3-, in the ECF, and therefore has little effect; however, in the ICF, it has a much more important role in maintaining pH. Additionally, cells contain a phosphate reserve in the form of the weak base Na2HPO4, which provides additional HPO4(-2). This system is also important for urine pH stabilization. |
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where and how does the protein buffer system work? |
1) in the ICF, c -NH2 and -COO- groups accepting H+ as weak bases to offset the acid production of cellular metabolism, or as -COOH, acting as a weak acid when pH rises. 2) by similar manner in the ECF, when at normal pH, where most -COOH have already given up their H+, histidine and cysteine retain their's and can donate when pH climbs beyond norm. But the prots that have given up their H+ can still act as weak bases for when pH lowers. 3) ICF prot buffer systems can also help ECF, albeit very slowly as this requires the intracellular H+ to be pumped out one-by-one. |
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where does the hemoglobin buffer system work and what makes it unique? |
- it's the only intracellular buffer system that can have an immediate effect on the ECF pH. Hb inside of RBCs buffer/absorb the H+'s that result from the carbonic acid dissociation, while the HCO3- diffuse out into the plasma in exchange for Cl-. |
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how does the carbonic acid-bicarbonate buffer system work? |
- this system prevents changes in pH caused by organic acids and fixed acids in the ECF. Because the rxn is freely reversible, a change in any one participant affects the [ ]'s of all others. When H+'s are added they're buffered by the HCO3-, turning into H2CO3, c HCO3- acting as a weak base. The H2CO3 can then be converted to CO2 and H2O at the lungs for excretion. |
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what are the 3 limitations of the carbonic acid-bicarbonate buffer system? |
1) it cannot protect the ECF from changes in pH resulting from incr or decr levels of CO2. A buffer system cannot protect against changes in the [ ] of its own weak acid. 2) it can fxn only when the respiratory system and the respiratory control centers are working normally. An incr in Pco2 must be able to trigger and incr in RR to remove excess CO2 and therefore H+'s. 3) the ability to buffer acids is limited by the availability of HCO3-'s. H+'s are removed by HCO3-'s, one-for-one. So, when HCO3-'s are depleted H+'s cannot be removed. |
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what helps ensure that the carbonic acid-bicarbonate buffer system retains enough HCO3- to continue working? |
- body fluids contain large reserves of HCO3- in the form of NaHCO3, which is known as the bicarbonate reserve. The body can also produce additional HCO3- from the exchange of H+ and Cl-, as HCl, for the HCO3- that comes from the carbonic acid dissociation within the tubular cells of the kidneys. |
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how does respiratory compensation work to maintain pH homeostasis? |
- chemoreceptors in the carotid and aortic bodies sense an incr or decr in Pco2 in circulating blood, and other chemoreceptors of the medulla oblongata monitor CSF for the same. These direct the incr or decr in RR, respectively, which decr and incr the Pco2, respectively. This directly effects the carbonic acid-bicarbonate buffer system brining about a in incr or decr in pH, respectively. |
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how does the renal compensation work? |
- a change in the rates of H+ and HCO3- secretion and absorption by the kidneys, follows changes in plasma pH. The kidneys also secrete CO2 that enters the renal tubules during filtration or diffusion as it travels towards the renal pelvis. The H+'s are secreted along the PCT, DCT, and collecting system, but their secretion is limited by the pH of the tubular fluid and therefore by the buffers present in the tubular fluid. |
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what buffers are at work in the tubular fluid to allow H+ secretion to continue working? |
- the carbonic acid-bicarbonate system; the phosphate buffer system; and the ammonia buffer system. |
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how does the H2CO3-HCO3 buffer system work within the kidneys? |
- H+ are pumped into the lumen of the renal tubule singularly or along c Cl-, both in exchange for Na+. CO2 is pumped out as well and HOC3- is moved to peritubular caps. |
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how does the ammonia buffer system work within the kidneys? |
- glutaminase inside tubule cells breaks down glutamine into either ammonium (NH4+) or ammonia (NH3). The NH4+ is secreted into the lumen and passes c urine. The NH3 is secreted into the lumen where it picks up a H+ to become NH4+ and passed in the urine. |
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how does the phosphate buffer system work within the kidneys? |
- as monohydrogen phosphate is in the urine it's able to accept secreted H+'s and bind them up to pass c the urine. |
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in what ways does renal compensation contribute to pH homeostasis? |
1) secretion of H+ 2) the activity of buffers in the tubular fluid. 3) the removal of CO2. 4) the resorption of NaHCO3. |
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what is the renal response to alkalosis? |
1) decr secretion rate of H+. 2) stops resorbing HCO3- from tubular fluid. 3) the collecting system trx HCO3- to the tubular fluid and releases the strong acid HCl into peritubular fluid. |
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what allows the ECF pH to be normal while its Pco2 is abnormal? |
- compensation. |
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when does respiratory acidosis occur and what is its primary sign? |
- when the respiratory system cannot eliminate all the CO2 produced by the peripheral tissues. Low blood pH due to hypercapnia will be noted. |
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what is acute respiratory acidosis? |
- an immediate, life-threatening condition, brought on by the severe decrease in pH, as a result of hypoventilation. |
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what is chronic respiratory acidosis? |
- normal respiratory fxn has been compromised, but the compensatory mechanisms have not failed completely, as in CNS injuries, and alcohol or barbiturate use. Or c intact respiratory centers, damage to the respiratory system as in pneumothorax, respiratory m. paralysis, emphysema, etc. |
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what is respiratory alkalosis? |
- respiratory activity creates hypocapnia. This generally fixes itself though, as respiratory drive is lowered to the point of pH returning to normal. |
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metabolic acidosis is caused by what? and how common is it? |
- it's the second most common acid-base imbalance. Its caused by: 1) the most widespread cause is the production of organic or fixed acids brought on by: -lactic acidosis- caused by anaerobic respiration from strenuous exercise or prolonged tissue hypoxia. -ketoacidosis- from metabolizing lipid and ketone bodies. 2) impaired kidney excretion of H+'s due to glomerulonephritis or diuretics that turn off the Na-H trx pump. 3) severe HCO- loss due to chronic diarrhea. |
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what is combined respiratory and metabolic acidosis? |
- O2 starved tissues generate large quantities of lactic acid, thereby causing acidosis from respiratory insufficiency and metabolic pathways. |
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what can cause metabolic alkalosis? |
- an increase in HCO3-, as a result of: 1) the alkaline tide due to the influx of many HCO3-'s into the ECF assoc c the secretion of HCl by the gastric mucosa. This increases the [HCO3-] of the ECF during meals. 2) Vomiting can also cause it due to a continual secretion of stomach acids to replace those that are lost. An increase in ECF [HCO3-] continues as a result. |
