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112 Cards in this Set
- Front
- Back
What percent of an infant is water?
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73%
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What happens to total water content throughout life?
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It decreases
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Healthy males are about ___ percent water, while females are about ___ percent water.
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60%, 50%
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Why do females have less total water content than males?
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1) Higher body fat
2) Smaller amount of skeletal muscle |
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In old age, what percentage of the body is water?
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About 45%
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What are the four main influencing factors regarding water content?
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1) age
2) gender 3) body fat 4) weight |
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What two major compartments does water occupy?
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1) Intracellular fluid
2) Extracellular fluid |
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What percentage of our total water content is contained in intracellular fluid?
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about 66%
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What are the two major subcompartments of the extracellular fluid?
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1) Plasma
2) Interstitial fluid |
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What are other examples of extracellular fluid (ECF)?
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lymph, cerebrospinal fluid, eye humors, synovial fluid, serous fluid, gastrointestinal secretions
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What percentage of the ECF is found in plasma?
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20%
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What percentage of the extracellular fluid (ECF) is found in interstitial fluid?
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80%
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Roughly how many liters of water does the average body hold?
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40L
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Solutes are broadly classified into which two categories?
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Electrolytes and nonelectrolytes
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Which has greater osmotic power: electrolytes or nonelectrolytes?
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electrolytes
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What are the major cations and anions in extracellular fluids?
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Sodium is the chief cation
Chlorine is the chief anion |
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What are the major cations and anions in intracellular fluids?
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Potassium is the chief cation
Phosphate is the chief anion |
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What substances determine the physical and chemical reactions of fluids?
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electrolytes
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Proteins, phospholipids, cholesterol, and neutral fats account for what percentage of the solutes in plasma?
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90%
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Proteins, phospholipids, cholesterol, and neutral fats account for what percentage of the solutes in interstitial fluid?
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60%
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Proteins, phospholipids, cholesterol, and neutral fats account for what percentage of the solutes in the intracellular compartment?
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97%
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Fluid movement among compartments is determined by which two pressures?
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Osmotic and hydrostatic pressures
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What system picks up leaked fluid from the blood and returns it to the bloodstream?
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lymphatic system
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What is the only fluid that circulates throughout the body and links external and internal environments?
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Plasma
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What moves relatively freely between intracellular compartments and interstitial fluid?
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water
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How do ion fluxes move between the intracellular compartment and the interstitial fluid?
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Active transport
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Nutrients, respiratory gases, and wastes move _______ between the intracellular compartment and interstitial fluid.
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unidirectionally
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What is the average necessary daily water input for an adult?
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2.5L
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How much of water intake comprises ingested fluid?
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60%
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How much of water intake comprises solid food?
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30%
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How much of water intake comprises metabolic water or water of oxidation?
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10%
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What organs/systems are responsible for water output?
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1) lungs
2) GI tract 3) Skin 4) Kidneys |
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Urine makes up what portion of total fluid lost?
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60%
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What percentage of total fluid lost comes from feces?
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4%
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What percentage of total fluid lost comes from insensible losses?
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28%
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Define thirst.
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Thirst is a deep-seated sensation of a desire for water
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List in detail the specific hypothalamic stimuli for thirst.
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1) Decline in plasma volume of 10%-15%
2) Increase in plasma osmolarity of 1-2% 3) Baroreceptor input 4) Angiotensin II |
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What factors inhibit thirst?
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Distension of the GI tract and then osmotic signals
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On average, how much urine does one output daily?
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500 mL
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Electrolyte balance refers to what?
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Salt balance (even though there are many kinds of electrolytes)
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What are salts important for?
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1) Neuromuscular excitability
2) Secretory activity 3) Membrane permeability 4) Controlling fluid movements |
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Why are omega 3s important?
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1) Help us lose weight
2) Help reduce cancer risk 3) They are critical in brain development for children |
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What are some important sources of bases?
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Bananas, chocolate, figs, mineral water, potatoes, spinach, watermelon, turnip greens
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What are some important sources for amino acids?
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meat, poultry, fish, eggs, milk, beans
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Where in the kidneys does sodium reabsorption take place?
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65% happens in the proximal tubules, 25% occurs in loops of Henle
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What steroid hormone encourages the body to actively reabsorb all sodium?
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Aldosterone
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What hormone encourages reabsorption of water along with sodium?
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ADH (antidiuretic hormone)
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What mechanism triggers the release of aldosterone?
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the renin-angiotensin mechanism
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What microscopic part of the kidney is responsible for renin release (and thus responsible for the release of angiotensin II, and thus aldosterone)?
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Juxtaglomerular apparatus -- it releases renin due to sympathetic nervous system stimulation, filtrate osmolarity, and decreased stretch (due to decreased blood pressure)
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What cells are directly stimulated to release aldosterone due to increased K+ levels in the ECF?
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Adrenal cortical cells
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What are the effects of aldosterone?
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diminished urine output and increased blood volume -- it takes effect very slowly
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What do baroreceptors detect?
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Blood pressure
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What happens when baroreceptors detect increased blood pressure?
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1) Sympathetic nervous system impulses to the kidneys decline
2) Afferent arterioles dilate 3) Glomerular filtration rate rises 4) Sodium and water output increase |
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Since sodium ion concentration determines fluid volume, what do baroreceptors indirectly detect?
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Sodium
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Does ANP increase or decrease blood pressure?
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decrease
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How does ANP (Atrial Natriuretic Peptide) reduce blood volume and pressure?
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By inhibiting sodium and water retention and by inhibiting events that promote vasoconstriction
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What prompts ANP (Atrial natriuretic peptide) to be released?
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An increase in stretch in the heart atria
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What effect does ANP have?
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Increased urine and fluid output
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What hormone does ANP (Atrial natriuretic peptide) inhibit?
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antiotensin II
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What percentage of filtered K+ is lost to urine output?
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15%
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How is potassium balance controlled?
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By adjusting the cortical collecting ducts potassium secretion into filtrate. When K+ levels are low, the amount of secretion and excretion is kept to a minimum.
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What kind of cells can reabsorb some K+ left in the filtrate?
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Type A intercalated cells
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What humoral factor influences principal cells to excrete K+?
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High levels of potassium in the ECF
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What hormone stimulates potassium ion secretion by principal cells?
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Aldosterone
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In cortical collecting ducts, one K+ is secreted for every ____ reabsorbed.
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Na+
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What influence does increased K+ in the ECF of the adrenal cortex have?
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It stimulates the release of aldosterone and potassium secretion
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What two hormones control calcium balance?
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Calcitonin and PTH (parathyroid hormone)
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PTH (parathyroid hormone) increases calcium levels by targeting:
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1) Bones (activates osteoclasts to break down bone matrix)
2) Small intestine (enhances intestinal absorption of calcium) 3) Kidneys (enhances calcium reabsorption and decreases phosphate reabsorption) |
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What type of relationship do calcium reabsorption and phosphate secretion have?
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Inverse
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Where is filtered phosphate actively absorbed?
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Proximal tubules
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In the absence of PTH, what regulates phosphate reabsorption?
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Transport maximum --- once that is reached, excesses are expelled in urine
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What does a lower PTH secretion level mean for calcium and phosphate levels?
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Release of calcium from bone is inhibited, more calcium is expelled in feces and urine, and more phosphate is retained
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What humoral stimules induces calcitonin release?
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Rising blood calcium levels -- though its role in calcium and phosphate homeostasis is negligible
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What's the fourth most abundand cation in the body?
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magnesium
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Where is 60% of magnesium in the body found?
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Bones
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What percentage of magnesium is found in bone?
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60%
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What percentage of magnesium is found in ECF?
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1%
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approximately what percentage of magnesium is found in ICF?
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40%
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What roles does magnesium play in the human body?
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1) It plays a role in immune function
2) it improves oxygen delivery to the heart 3) It prevents formation of kidney stones 4) it helps treat ischemic heart disease |
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Where does regulation of excess magnesium occur?
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the kidney
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Where does most reabsorption of magnesium occur?
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In the loop of henle
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What controls the reabsorption of magnesium?
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Mostly its plasma concentration
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About how much magnesium passing through the kidney is reabsorbed?
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About 95%
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About how much filtered magnesium is filtered in the glomerulus?
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About 75%
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Define "base."
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A class of compounds opposite to acids, in that they neutralize acids.
They are substances that bond readily with hydrogen ions. |
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Define "alkalosis."
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A condition in which the blood has a lower concentration of hydrogen ions than normal, and a higher pH level is measured
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Alkalosis or Alkalemia is in effect when blood pH rises above what level?
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7.45
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What's the normal pH of arterial blood?
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7.4
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What's the normal pH of venous blood and interstitial fluids?
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7.35
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What's the normal pH of intracellular fluids?
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7.0
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How do most hydrogen ions originate?
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Cellular metabolism
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What are the three sequential steps of hydrogen ion regulation?
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1) Chemical buffer systems (which act within seconds)
2) Respiratory center in the brain stem (which acts in 1-3 minutes) 3) Renal mechanisms (which require hours or even days to effect changes) |
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Define chemical buffer systems
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One or two molecules that act to resist pH changes when strong acid or base is added.
Major systems include the bicarbonate buffer system, phosphate buffer system, and protein buffer system |
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What are the three major chemical buffer systems?
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1) Bicarbonate buffer system
2) Phosphate buffer system 3) Protein buffer system |
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What acid and base make up the bicarbonate buffer system (which happens to be the only truly important ECF buffer)?
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Carbonic acid (H2CO3)
Sodium Bicarbonate (NaHCO3) |
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What are the acid and base that make up the phosphate buffer system (which is effective in urine and ICF)?
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Sodium salts of dihydrogen phosphate (acid) (H2PO4)
Monohydrogen phosphate (HPO4) |
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Where is the phosphate buffer system effective?
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ICF and urine
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What's an amphoteric molecule?
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It's a protein molecule that acts as a buffer and can take the role of either a weak acid or a weak base
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How does the respiratory system regulate pH?
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It takes advantage of a reversible equilibrium between CO2 and H20 --- and carbonic acid and the hydrogen and bicarbonate ions
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Define "hypercapnia."
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excessive CO2 in the blood
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How does the respiratory system combat hypercapnia (excessive CO2 that results in acidosis)?
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More rapid breathing
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What effect does alkalosis have on breathing?
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Breathing slows, causing H+ to increase and pH to decrease
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What are the ultimate acid-base regulating organs?
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the kidneys
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What's the only organ that can rid the body of metabolic acids (phosphoric, uric, and lactic acids, plus ketones) and prevent metabolic acidosis?
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the kidney
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What are the two most important renal mechanisms for regulating acid-base balance?
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1) Reabsorbing or generating bicarbonate ions
2) Excreting bicarbonate ions |
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Where do hydrogen ions come from?
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secretion in the PCT and in type A intercalated cells, from the dissociation of carbonic acid
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What's the most common cause of acid-base imbalance?
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Respiratory acidosis due to hampered gas exchange
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What's a common result of hyperventilation?
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Respiratory alkalosis
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What's the normal range for bicarbonate ion levels?
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22-26 mEq/L
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What's the second most common form of acid-base imbalance?
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metabolic acidosis
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What are some common causes of metabolic acidosis?
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Alcohol consumption, excessive loss of bicarbonate ions, accumulation of lactic acid, shock, ketosis, starvation, and kidney failure
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What are common causes of metabolic alkalosis?
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Vomiting out the acidic contents of the stomach, intake of excessive antacids, constipation and thus excessive bicarbonate reabsorption
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