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Pathophysiology

Ch 3 - The Cellular Environment: Fluids, Electrolytes, Acids, and Bases

QuestionAnswer
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