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Pathophysiology
Ch 3 - The Cellular Environment: Fluids, Electrolytes, Acids, and Bases
| Question | Answer |
|---|---|
| What is the definition of total body water? | Sum of all the fluids in the body. Composed of intracellular fluid and extracellular fluid |
| What is extracellular fluid? | interstitial fluid, intravascular fluid, lymph, synovial, intestinal, csf, sweat. etc. |
| What is the formula for net filtration? Starling hypothesis. | Net filtration= forces favoring filtration- forces opposing filtration |
| What are forces favoring filtration? | Capillary hydrostatic pressure (blood pressure) Interstitial oncotic pressure (water pulling) |
| What are the forces favoring reabsorption (not favoring filtration)? | Plasma oncotic pressure (water pulling) Interstitial hydrostatic pressure |
| What is edema? | Accumulation of fluid within the interstitial apaces. Fluid distribution problem not necessarily excess fluid |
| What are some causes of edema? | Increase in capillary hydrostatic pressure Decrease in capillary oncotic pressure Increase in capillary permeability Lymph obstruction |
| What receptors trigger increase in thirst perception? | Osmolality receptors. Causes hyperosmolality, dry mouth, plasma volume decreases |
| What receptors trigger ADH secretion? | Baroreceptors and osmoreceptors |
| Explain how ADH works? | Plasma osmolality increase or circulating fluid increase trigger ADH secretion which causes water retention. This results in an increase in circulating fluid volume. |
| What is the primary ECF cation? | Sodium. It regulates osmotic forces. |
| What is the primary ECF anion? | Chloride. Provides electroneutrality. |
| explain the relationship between chloride, sodium and bicarbonate | Transport of chloride is generally passive and follows the active transport of sodium. Chloride levels tend to change inversly proportional to bicarbonate. |
| How does the renin-angiotensin-aldosterone system work? | When circulating blood volume or blood pressure decreases, renin is released. Renin stimulates formation of angiotensin. Angiotensin stimulates secretion of aldosterone which promotes sodium and water reabsorption conserving blood volume. |
| What are isotonic alterations? | Total body water changes with proportional electrolyte change. |
| What are the types of isotonic alterations? | Isotonic volume depletion Isotonic volume excess |
| What are the three types of hypertonic alterations? | Hypernatremia, water deficit, hyperchloremia |
| What is hypernatremia? | It is related to sodium gain or water loss. Causes water movement from the ICF to ECF. Results in intracellular dehydration |
| What are some manifestison of hypernatremia? | intracellular dehydration, convulsions, pulmonary edema, hypotension, tachycardia |
| What is water deficit caused by? | Dehydration, pure water deficits, renal free water clearance. |
| What are some manifestations of water deficit? | Tachycardia, weak pulse, and postural hypotension. Elevated hematocrit and serum sodium levels. |
| Describe hyperchloremia | Occurs with hypernatremia or a bicarboante deficit, usually secondary to pathophysiologic process. Managed by treating underlying disorders. |
| What are the characteristics of hypotonic alterations? | decreased osmolality. hyponatremia or free water excess. decreases ECF osmotic pressure and water moves into the cell. |
| Describe hyponatremia | Serum sodium level less than 135 mEq/L Sodium deficits cause plasma hypoosmolality and cellular swelling |
| Describe some causes of water excess | Compulsive water drinking. Decreased water formation. Syndrome of inappropriate ADH (SIADH) |
| What are some manifestations of water excess? | Cerebral edema, muscle twitching, headache, and weight gain |
| What are some causes of hypochloremia? | Usually the result of hyponatremia or elevated bicarbonate concentration. Develops due to vomiting and the loss of HCl. Occurs in cystic fibrosis. |
| What are the functions of potassium? | Essential for transmission adn conduction of nerve impulses, normal cardiac rhythms, and skeletal and smooth muscle contraction |
| What affects Potassium balance? | Changes in pH affect potssium levels. Hydrogen ions accumulate in ICF during states of acidosis. Potassium shifts out to maintain a balance of cations across the membrane. |
| What do baroreceptors sense? | Plasma volume depeletion. Triggers release of ADH. |
| How is the concentration of potassium maintained? | Through the sodium-potassium pump. |
| Potassium regulates intracellular electrical neutrality in relation to what? | Sodium and H+ |
| What are the functions of potassium? | Essential for transmission adn conduction of nerve impulses, normal cardiac rhythms, skeletal and smooth muscle contractions. |
| HOw do potassium concentrations react to changes in pH? | Hydrogen ions accumulate in the ICF during states of acidosis. Potassium shifts out to maintain a balance of cations across the membrane. |
| What other substances influence serum potassium levels? | Aldosterone, insulin, and catecholamines |
| What is hypokalemia? | Potassium levels less than 3.5 mEq/L |
| What are some causes of hypokalemia? | reduced potassium intake, increased potassium entry, increased potassim loss |
| What are some manifestations of hypokalemia? | membrane hyperpolarization. causes a decrease in neuromuscular excitability, skeletal muscle weakness, cardiac dysrhythmias. |
| What is hyperkalemia? | Potassium levels greater than 5.5 mEq/L |
| Why is hyperkalemia rare? | Efficient renal excretion normally takes care of any excess potassium |
| What are some causes of hyperkalemia? | increased potassium intake, shift of potassium from ICF, decreased renal excretion, insulin deficiency, or cell trauma |
| Describe some symptoms of mild attacks of hyperkalemia | Hypoploarized membrane causing neuromuscular iritability. Tingling of lips and fingers. Intestinal cramping and diarrhea |
| What are some characteristics of severe attacks of hyperkalemia? | The cell is unable to repolarize resulting in muscle weakness, loss of muscle tone, flaccid paralysis, and cardiac arrest. |
| How is most calcium in the body stored? | Most calcium is located in the bones as hydroxyapatite |
| What are some necessary functions of calcium? | Necessary for structure of bones and teeth, blood clotting, hormone secretion, and cell receptor function. |
| Where is most phosphate in the body stored? | In the bones |
| What are some functions of phosphate? | Necessary for high energy bonds located in creatine phosphate and ATP. Acts as an anion buffer. |
| How are calcium and phosphate conectrations related? | If the concentration of one increases, that of the other decreases. |
| What are the three hormones that calcium and phosphate are regulated by? | Parathyroid hormone (PTH) Vitamin D Calcitonin |
| How does parathyroid hormone (PTH) function? | It increases plasma calcium levels via bone reabsorption |
| How does vitamin D function? | It is a fat soluble steroid. It increases calcium absorption from the GI tract |
| How does calcitonin function? | It decreases plasma calcium levels. |
| What are some results of hypocalcemia? | decreases the block of sodium into the cell. Increased neurmuscular excitability (partial depolarization), muscle cramps |
| What are some effects of hypercalcemia? | Increases the block of sodium into the cell. Decreased neuromuscular excitability, muscle weakness, increased bone fractures, kidney stone, constipation |
| What are some effects of hypophosphatemia? | Osteomalacia (soft bones), muscle weakness, bleeding disorders, anemia, leukocyte alterations |
| What are some characteristics of hyperphosphatemia? | Increased neuromuscular excitability (partial depolarization) muscle cramps. |
| What is a normal range for plasma magnesium concentration? | 1.8 to 2.4 mEq/L |
| What are some functions of magnesium? | Acts as a co-factor in protein and nucleic acid synthesis reactions. Required for ATPase activity. Decreases acetylcholine release at the neuromuscular junction. |
| What are some effects of hypomagnesemia? | Neuromuscular irritability, tetany, convulsions, hyperactive reflexes. Associated with hypocalcemia and hypokalemia. |
| What are some effects of hypermagnesemia? | Skeletal muscle depression, muscle weakness, hypotension, respiratory depression, lethargy and drowsiness. |
| What is the definition of pH? | The negative logarithm of the hydrogen ion concentration |
| A solution that moves from a pH of 7 to a pH of 6 has how much of an increase in hydrogen ions? | A 10 fold increase. |
| What is the numeric range of pH? | 0 to 14 |
| How are acids formed? | Acids are formed as end products of protein, carbohydrate, and fat metabolism. |
| What is the body's normal pH range? | 7.35-7.45 |
| What are the major organs involved in regulation of acid base balance? | Bones, lungs, and kidneys |
| What are the two forms of body acids? | Volatile and Nonvolatile |
| What is the volitile acid? | Carbonic Acid (H2CO3). It is a respiratory acid and can be eliminated as CO2 gas. |
| What are nonvolitile acids? | Metabolic acids. sulfuric, phosporic, and other organic acids. |
| How are nonvolitile acids eliminated? | eliminated by renal tubules with the regulation of bicarobonate. |
| How are volitile acids eliminated? | Eliminated as carbon dioxide gas from the respiratory system. |
| What is a buffer? | A chemical that can bind excessive H+ or OH- without a significant change in pH. Consists of a weak acid and its conjugate base. |
| Whate are the most important plasma buffering systems? | Carbonic acid-bicarbonate system and hemoglobin |
| Where does the carbonic acid-bicarbonate system funcion? | Lungs and Kidneys. |
| explain how the carbonic acid-bicarbonate system works. | The greater the partial pressure of carbon dioxide, the more carbonic acid is formed |
| What is the ratio of carbonic acid to bicarbonae that must be maintained? | 20:1 |
| How does the respiratory system compensate for pH changes? | Increasing or decreasing ventilation |
| How does the renal system compensate for changes in pH? | producing acidic or alkaline urine |
| How does protein buffering work? | Proteins have negative charges sot hey can serve as buffers for H+. Primarilly an intracellular buffer. |
| How does cellular ion exchange work as a buffer? | exchange of potassium for H+ in acidosis and alkalosis. Alters serum potassium. |
| What is respiratory acidosis? | elevation of pco2 due to ventilation depression |
| What is respiratory alkalosis? | depression of pco2 due to alveolar hyperventilation |
| What is metabolic acidosis? | Depression of HCO3- or an increase in noncarbonic acids |
| What is metabolic alkalosis? | elevation of HCO3- usually due to an excessive loss of metabolic acids |
| What is compensation? | When adjustments are made to bicarbonate and carbonic acid in order to maintain the 20:1 ratio and maintain normal pH. The actual values for bicarbonate and carbonic acid are not normal but the normal ratio is achieved. |
| What is correction? | Correction occurs when the calues for carbonic acid and bicarbonae have returned to normal levels. |
| What is the anion gap used for? | To distingues different types of metabolic acidosis |
| What is a normal anion gap? | 10-12 mEq/L |
| What would cause an abnormal anion gap? | increased level of abnormal unmeasured anion. Examples: ketones, salicylate poisoning, lactic acidosis, renal failure, etc. |
| How would an increase in abnormal ions affect the measured anions? | as abnormal anions accumulate, the measured anions have to decrease to maintain electroneutrality. |
Created by:
MEPN 2013
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