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examples of fluid sequestration?
- ascites (lose in belly)
- pleural effusions,
- pulmonary edema- fluid collections are hiding from (sequestered) the body's normal mechanism for regulating fluid volume
what is an acid?
a molecule that gives up a hydrogen ion in solution
what is pH?
negative logarithm of the hydrogen ion concentration
what is a buffer system?
a chemical reaction with a substrate that is a base that will convert a strong acid to a weak one. by binding the hydrogen produced by the strong acid, the free hydrogen concentration is reduced and the level of acidity decreases
what is the usual cause of hypernatremia? of hyponatremia?
- hyper- too little water
- hypo- too much water
- (Changes in the blood level of sodium are due to changes in water, not sodium)
what is the effect of changes in potassium?
- changes in cell membrane resting potential -
- hyperkalemia causes cells (especially cardiac muscle) to be hyper-excitable;
- hypokalemia causes cells to be harder to excite
why do all cells contain calcium pumps in their membranes?
calcium must be excluded from the cytoplasm to keep it from combining with phosphate
how does hyperventilation cause tetany?
- produces alkalosis which increases binding of calcium to protein, lowering the free (usable) calcium.
- Hypoglycemia causes the resting membrane potential to rise closer to threshold, making more muscle cells easier to depolarize.
- as it progresses, muscle cells depolarize continuously, producing tetany.
how do renal and respiratory buffering work?
- the lungs remove carbon dioxide which causes more hydrogen to combine with bicarbonate.
- the kidneys excrete hydrogen (acid) and reabsorb bicarbonate (the base)
describe the disorders of acid-base imbalance?
- metabolic acidosis- more acid, hydrogen ions, produced than can be buffered (diabetes)
- respiratory acidosis- lungs not getting rid of enough carbon dioxide (emphysema)
- metabolic alkalosis- excessive loss of acid (protracting vomiting)
- respiratory alkalosis- below normal level of carbon dioxide (hyperventilation)
what are the body's methods for compensating for acid-base imbalance?
- increase or decrease respiratory rate by the lungs
- increase hydrogen excretion by the kidney
- increase bicarbonate excretion by the kidney