3 week 18 Flashcards
what is pH? what is normal arterial plasma pH?
- measure of hydrogen ions
- 0.00004 mM or 7.35-7.45
what pH is considered acidosis? alkalosis?
- pH less than 7.35 = acidosis
- pH greater than 7.45 = alkalosis
why can a change in arterial blood pH have profound effects on body function?
because it alters the pH of fluids throughout the body
what are the sources of H+ and main ways to remove it from the body?
- input: diet, metabolism
- output: kidneys, lungs
decrease in CO2 = ____ in hydrogen ions, ___ing pH
decrease, increasing
what are 3 ways to regulate pH? how long does each way take?
- buffering of hydrogen ions (quickest)
- respiratory compensation (minutes)
- renal compensation (hours to days)
what are the most common ICF buffers? ECF?
- ICF buffers = proteins, phosphates
- ECF buffer = bicarbonate
what effect does increased ventilation have on CO2 and pH? what about decreased ventilation?
- increased ventilation = decreased CO2 (increased pH)
- decreased ventilation = increased CO2 (decreased pH)
how do decreases in plasma pH increase ventilation?
- decrease in plasma pH (+acidity) is detected by peripheral and central chemoreceptors
- chemoreceptors increase ventilation which decreases plasma CO2
- decrease in plasma CO2 = increased pH
what are the 2 key steps of renal regulation
- regulate excretion of hydrogen ions and bicarbonate in urine
- regulate synthesis of new bicarbonate in renal tubules
what happens at the proximal tubule vs the distal tubule/collecting duct?
- PROXIMAL TUBULE
- bicarbonate reabsorption coupled to hydrogen ion secretion
- …
- DISTAL TUBULE/COLLECTING DUCT
- acidosis: secretion of hydrogen ions + synthesis of new bicarbonate ions
- OR
- alkalosis: secretion of bicarbonate + reabsorption of hydrogen ions
describe the details of how bicarbonate reabsorption is coupled to hydrogen ion secretion (3)
- filtered bicarbonate combines with secreted H to form carbonic acid, which is converted to water and CO2 by carbonic anhydrase on the apical membrane.
- CO2 diffuses into epithelial cell, where intracellular carbonic anhydrase catalyzes the conversion of CO2 and water to carbonic acid; the carbonic acid then dissociates into bicarbonate and H.
- H ions are secreted by countertransport with Na ions, whereas the bicarbonate is reabsorbed by cotransport with Na and by countertransport with Cl.
describe the details of bicarbonate production and hydrogen secretion by glutamine metabolism? when does this occur? (4)
- occurs in proximal tubule when acidosis is severe.
- glutamine is catabolized to bicarbonate ions + ammonia.
- bicarbonate ions are transported into peritubular fluid by a Na+/HCO3 cotransporter or a HCO3/Cl countertransporter.
- ammonia binds a H ion to form ammonium, which is secreted by countertransport with Na ions.
describe the details of what happens during acidosis in the distal tubule/collecting duct (3)
- RE: bicarbonate synthesis + hydrogen ion secretion
- carbonic anhydrase in the cytosol converts CO2 into carbonic acid, which dissociates into H ions and bicarbonate ions.
- the H ions are secreted by a H pump or a K/H countertransporter; the bicarbonate ions are transported into the peritubular fluid by a HCO3/Cl countertransporter.
describe the details of what happens during alkalosis in the distal tubule/collecting duct (3)
- RE: bicarbonate secretion and hydrogen ion reabsorption
- bicarbonate ions are secreted into the tubular fluid by type B intercalated cells in the collecting duct.
- H-ATPase pump pumps H ions into the peritubular fluid.
what causes respiratory acidosis? what is the compensation?
- cause: hypoventilation (drugs, asthma, resp muscle weakness)… basically increased CO2 + increased H
- compensation: (renal) increased H excretion and increased HCO3 reabsorption
what causes respiratory alkalosis? what is the compensation?
- cause: hyperventilation (panic attack, too much mechanical ventilation)… basically decreased CO2 + decreased H
- compensation: (renal) increased H reabsorption and increased HCO3 excretion
what causes metabolic acidosis? what is the compensation?
- cause: decreased pH through something other than CO2 (high-protein/fat diet, heavy exercise, severe diarrhea, renal dysfunction)… basically too much H and too little bicarbonate
- compensation: (resp) = +ventilation (-CO2) and (renal) = increased H secretion, increased HCO3 reabsorption, increased bicarbonate synthesis
what causes metabolic alkalosis? what is the compensation?
- cause: increased pH through something other than CO2 (excessive vomiting, consumption of alkaline products, renal dysfunction)… basically too little H and too much bicarbonate
- compensation: (resp) = -ventilation (+CO2) and (renal) = decreased H secretion, decreased HCO3 reabsorption, decreased synthesis of new bicarbonate
what is the ratio for…
a) pH = 7.4
b) acidosis
c) alkalosis
a) 20:1
b) < 20:1
c) > 20:1
what is the ECF concentration of calcium? ICF? bone?
- ECF: 0.1%
- ICF: 0.9%
- bone: 99%
which 3 hormones control plasma calcium concentration?
- parathyroid hormone (PTH)
- calcitriol
- calcitonin
key functions of PTH (4)
- increases plasma calcium
- stimulated by low calcium concentrations
- targets kidney and bone
- is a peptide hormone
key functions of calcitriol? (4)
- increases plasma calcium
- stimulated by PTH + low calcium concentrations
- targets digestive tract and kidney
- is a steroid hormone synthesized from vitamin D3 (PTH catalyzes it into calcitriol)
key functions of calcitonin? (4)
- decreases plasma calcium
- stimulated by high calcium concentrations
- secreted from C cells of the thyroid gland
- is a peptide hormone
we know that calcitonin decreases plasma calcium. what does this mean for bones and the kidneys?
- calcium goes to bones instead of plasma, increases bone deposition and inhibits bone resorption
- also inhibits calcium reabsorption at kidneys and increases urinary excretion
when there is high plasma calcium, calcium can be ____________.
when there is low plasma calcium, calcium can be ____________.
- deposited into bone (via osteoblasts) or excreted
- liberated through bone resorption (via osteoclasts)
what are the 3 types of osteoporosis?
- disuse osteoporosis: e.g., due to immobilization or space flight.
- primary osteoporosis: particularly occurs among post-menopausal women (loss of estrogen results in greater osteoclast activity).
- secondary osteoporosis: results of some other disorder (e.g., hyperthyroidism).
what are some treatments for osteoporosis? (3) what is the best preventative measure?
- estrogen therapy
- calcium supplements
- vitamin D
best preventative measure = exercise!
