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Ch-26 Fluid, Electrolyte, & Acid-Base Balance
Which tissue is least & most hydrated
Consists of trillions of tiny individual compartments
Intracellular fluid compartments
the bodys internal environment, external environment of each cell
extracellular fld compartment
The 2 subcompartments of ECF
1. Plasma-fluid portion of the blood
2. Interstitial Fluid-fluid between tissue cells
Have bonds that prevent them from dissociating in solution
chemical compounds that do dissociate into ions in water
How does water move?
according to osmotic gradients-from lesser osmolarity to an area of greater osmolarity
The one difference between the two extracellular fluid components
Plasma has more protein than interstitial fld
What are the most abundant ECF electrolytes?
Sodium, Chloride, and bicarbonate ions
What substances does ICF contain
Protein Anions, potassium, phosphate, and magnesium
What regulates fluid exchange between compartments?
osmotic and hydrostatic pressures
Filtrate is forced out of capillaries by?
and pulled back in by?
Filtrate is forced out of capillaries by hydrostatic pressure and pulled back in by colloid osmotic pressure
How does water move between ECF and ICF
Freely by osmosis
How are solute movements restricted?
size, charge, and dependence of transport proteins
Water flows always follow changes in what?
The hypothalamic thirst center is excited by what?
A increase 2-3% in plasma osmolarity
Three ways hypothalamic thirst center neurons are stimulated
osmoreceptors lose water by:
osmosis to the hypertonic ECF, activated by angiotensin II, by barorecptor inputs
What causes aquaporins to be inserted in the cell membranes of the collecting ducts?
The amount of water reabsorbed in the renal collecting ducts is ________ to ADH release
Diluted urine and a reduced volume of body fluids
Fever, excessive sweating, diarrhea, vomiting ..do what to ADH
Trigger it's release
Due to stress on the body, ADH also increases BP by?
Decreased urine output
water loss from plasma results in inadequate blood volume, unable to maintain normal circulation
In dehydration, water is lost from where?
Low ECF Na+
body fluids are excessively diluted, cells swollen...can result in cerebral edema
abnormally low level of protein in the blood, results in tissue edema
disorder entailing deficient mineralocorticoid hormone production by the adrenal cortex, can result in severe cravings for salty foods
Promotes sodium reabsorption and water conservation
When do the granular cells release Renin?
declining BP and falling filtrate osmolarity
Enhances systemic BP and aldosterone release
Angiotensin II (renin converted)
The cario baroreceptors sense changing arterial BP, prompting?
changes in sympathetic vasomotor activity
Rising Arterial pressure leads to?
vasodilation and enhanced sodium and water loss in urine
Falling arterial pressure leads to?
vasoconstriction, conserves sodium and water
What is the effect of Atrial Natriuretic Peptide?
released when BP is high, vasodilation, inhibits renin, aldosterone and ADH release. Enhances sodium and water excretion-reduces BV & BP
Increase Renal retention of sodium
Estrogens and glucocorticoids
Enhances sodium and water excretion in urine
About 90% of filtered potassium is reabsorbed by what structure?
proximal regions of the nephrons
Which cells secrete potassium?
What enhances K+ secretion by the principle cells?
Increased plasma K+ and aldosterone
During a K+ deficit which cells reabsorb small amounts of K+?
Type A cells of CD
Where does PTH regulated reabsorption occur?
Mainly in the DCT
PTH decreases renal absorption of what ion?
Declining plasma levels of calcium stimulate the parathyroid gland to release PTH, increases calcium by targeting which organs?
Bones, Small Intestine, and Kidneys
The major anion accompanying sodium in the ECF?
the pH of arterial blood rises above 7.45
Drop in arterial pH to below 7.35
In acidosis, which ion goes with sodium reabsorption?
Proton (H+) donors
3 ways acids are generated in the body
1. breakdown of phosphorus containing proteins
2. incomplete oxidation of fats or glucose
3. loading and transport of carbon dioxide in the blood
The only important ECF buffer
Bicarbonate Buffer system
Phosphate Buffer system is effective in buffering ? Ineffective?
Effective buffering urine in ICF (due to high phosphate concentrations)
Mose plentiful and powerful source of buffers
protein buffer system
protein can function as either an acid or base depending on the pH of its environment
What two things active the respiratory center?
Hypercapnia--- medullary chemoreceptors
rising plasma H+ concentrations
To counteract acidosis, either one of two mechanisms may be used
1. Secreted H+ in the urine
2. NH4+ excreted in urine
How is alkalosis counteracted?
Bicarbonate ion is secreted into the filtrate and H+ is absorbed
Results from CO2 retention
Occurs when CO2 is eliminated faster than it's produced
Occurs when fixed acids accumulate in the blood or when bicarbonate is lost
Occurs when bicarbonate levels are excessive
Involve changes in respiratory rate and depth
modify blood levels of HCO3-
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