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27- Homeostasis
Chapter 27- Fluid, Electrolyte, and Acid-Base Homeostasis
| Question | Answer |
|---|---|
| Intracellular fluid | also known as cytosol. Fluid within cells. Makes up 2/3 of body fluid |
| Extracellular fluid | makes up the remaning 1/3 of body fluid. Fluid outside cells. |
| Barriers that separate ICF | plasma membrane and blood vessel walls |
| Body can gain water by | - ingestion of liquids and moist foods - metabolic synthesis of water during cellular respiration and dehydration synthesis |
| Body loses water through | kidneys, evaporation from skin, exhalation from lungs, and feces |
| Regulation of Body Water Gain | mainly by volume of water intake/how much you drink |
| Dehydration | when water loss is greater than gain. Decrease in volume, increase in osmolarity of body fluids. Stimulates thirst center in hypothalamus |
| Hormones that regulate renal Na+ and Cl- reabsorption | angiotensin II & aldosterone (promote urinary Na+ and Cl- reabsorption) and atrial natriuretic peptide (promotes excretion of Na+ and Cl-) |
| Antidiuretic hormone (ADH) | Also known as vasopressin Produced by hypothalamus, released from posterior pituitary Promotes insertion of aquaporin-2 into principal cells of collecting duct Permeability to water increases Produces concentrated urine |
| Water Intoxication | Drinking water faster than the kidneys can excrete it. Can lead to convulsions, coma, or death |
| General function of electrolytes | - control osmosis of water between body fluid compartments - help maintain the acid-base balance - carry electrical current - serve as cofactors |
| Chief difference between ECF compartments (plasma and interstitial fluid) | plasma contains many more protein anions |
| ICF/ECF Differences | - ECF most abundant cation is Na+, anion is Cl- - ICF most abundant cation is K+, anions are proteins and phosphates (HPO42-) - Na+ /K+ pumps play major role in keeping K+ high inside cells and Na+ high outside cell |
| Sodium (Na+) | - Most abundant ion in ECF - 90% of extracellular cations - Plays pivotal role in fluid and electrolyte balance because it accounts for almost half of the osmolarity of ECF |
| Sodium level in blood is controlled by | aldosterone (increases renal reabsorption), ADH (if sodium is too low, ADH release stops), atrial natriuretic peptide (increase renal excretion) |
| Chloride (Cl-) | - most prevalent anion in ECF - moves relatively easily between ECF and ICF because most plasma membranes contain Cl- leakage channels and antiporters - can help balance levels of anions in different fluids |
| Chloride level is regulated by | ADH (governs extent of water loss in urine) and processes that increase or decrease renal reabsorption of Na+ also affect reabsorption of Cl- |
| Potassium (K+) | - most abundant cation in ICF - key role in establishing resting membrane potential in neurons and muscle fibers - helps maintain normal ICF fluid volume - helps regulate pH of body fluids when exchanged for H+ |
| Potassium level is controlled by | aldosterone (stimulates principal cells in renal collecting ducts to secrete excess K+) |
| Bicarbonate (HCO3-) | - second most prevalent extracellular anion - concentration increases in blood passing through systemic capillaries picking up carbon dioxide |
| Bicarbonate level is regulated by | the kidneys (can form and release HCO3- when low or excrete excess |
| Calcium (Ca2+) | - most abundant mineral in the body - plays important roles in blood clotting, neurotransmitter release, muscle tone, and excitability of nervous and muscle tissue - contributes to hardness of teeth and bones |
| Calcium level is regulated by | the parathyroid hormone stimulates osteoclasts to release calcium from bone, enhances reabsorption from glomerular filtrate, and increases production of calcitriol to increase absorption for GI tract |
| Calcitonin | lowers blood calcium levels |
| Phosphate | - about 85% of phosphate in adults is present as calcium phosphate salts in bone and teeth - same hormones governing calcium homeostasis also regulate HPO42- in blood |
| Phosphate level is regulated by | parathyroid hormone (stimulates resorption of bone by osteoclasts releasing calcium and phosphate but inhibits reabsorption of phosphate ions in kidneys) & calcitriol (promotes absorption of phosphates and calcium from GI tract) |
| Magnesium | - second most common intracellular cation - functions as a cofactor for certain enzymes and sodium-potassium pump - essential for normal neuromuscular activity, synaptic transmission, and myocardial function - secretion of PTH depends on Mg2+ |
| Mechanisms that help maintain pH of arterial blood between 7.35 and 7.45 | buffer systems, exhalation of CO2, and kidney excretion of H+ |
| Buffer Systems | - act to quickly temporarily bind H+ - raise pH but do not remove H+ - most consist of weak acid and salt of that acid functioning as weak base |
| Protein buffer system | - most abundant buffer in ICF and blood plasma - hemoglobin in RBCs - albumin in blood plasma - free carboxyl group acts like an acid by releasing H+ - free amino group acts as a base to combine with H+ |
| Carbonic acid-bicarbonate buffer system* | based on bicarbonate ion acting as weak base and carbonic acid acting as weak acid |
| Phosphate buffer system* | dihydrogen phosphate and monohydrogen phosphate |
| How to eliminate a huge acid load | excrete H+ in urine |
| Other buffers that can combine with H+ in collecting duct | HPO42= and NH3 |
| Acidosis | results in depression of synaptic transmission in CNS |
| Alkalosis | results in overexcitability of CNS and peripheral nerves |
| Respiratory acidosis | abnormally high PCO2 in systemic arterial blood |
| Respiratory alkalosis | abnormally low PCO2 in systemic arterial blood |
| Metabolic acidosis | abnormally low HCO3- in systemic arterial blood |
| Metabolic alkalosis | abnormally high HCO3- in systemic arterial blood |
Created by:
ariellebtan
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