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Homeostasis wk8 Fluid,electrolyte and acid-base balance

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winniesmith1's version from 2017-05-05 13:54

Section 1

Question Answer
What does osmolarity mean the concentration of a solution expressed as the total number of solute particles per litre.
What does isotonic mean denoting or relating to a solution having the same osmotic pressure as some other solution, especially one in a cell or a body fluid.
What does hypertonic mean having a higher osmotic pressure than a particular fluid- water moves out.
What does hypotonic mean having a lower osmotic pressure than a particular fluid- water moves in
What does diuresis mean increased or excessive production of urine
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Section 2

Question Answer
composition of adult male human body water 60% (intracellular fluid 33%, interstitial fluid 21.5% plasma 4.5%) Solids 40% (proteins, lipids, minerals, carbs, organic/inorganic materials)
composition of adult female human body water 50% (intracellular fluid 27%, interstitial fluid 18%, plasma 4.5%) Solids 50%
How is fluid lost from ECF urine (biggest loss), respiratory losses and insensible perspiration, fecal loses, sensible perspiration.
What are the cations in body fluid Na+, K+, Ca2+, Mg2+
What are the anions in body fluids HCO3-, Cl- , HPO4^2-, SO4^2-, organic acid and proteins
Compare osmolarity in ICF and ECF-ICF and ECF have identical osmolarity -Osmosis eliminates minor differences in concentration: cell membranes permeable to water -K+ ions mainly in ICF -Na+ ions mainly in ECF
What is a fluid shift Movement of water between ECF and ICF to balance osmolarity
When does fluid shift occur usually in response to changes in osmotic concentration of ECF.
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Section 3

Question Answer
Regulation of fluids and electrolytes: sodium balance Osmoreceptors in hypothalamus detect increase or decrease in Na+ concentration --> hormonal responses
What are the 3 fluid/electrolyte regulatory hormones. 1.antidiuretic hormone (ADH) 2.aldosterone 3.Atrial natriuretic peptide (ANP)
Describe ADH Secreted by anterior hypothalamus in response to increased Na+. --> increased water absorption in kidneys --> stimulates thirst centre --> increases fluid intake
Describe what happens when normal Na+ concentration in ECF increases and homeostasis disturbed osmoreceptors stimulated > increased ADH release, increased thirt > Decreased urinary water loss, increased water gain > additional water dilutes ECF, volume increased > homeostasis restored. (and vise versa)
Describe aldosterone Secreted by adrenal cortex in response to: rising K+ or falling Na+ levels in blood. Activation of renin–angiotensin system. Causes Na+ absorption and K+ loss (at distal convoluted tubule and collecting duct)
*look at nephron and collecting system. pg 17 acid-base lecture* Glomerulus in bowmans capsule, proximal convoluted tubule, loop of henle, distal convoluted tubule, collecting duct.
Describe water follows salt High aldosterone causes kidney to conserve Na+, conservation of Na+ also stimulated water retention.
Describe ANP (atrial natriuretic peptide)Released in response to increased blood volume. --> Reduced thirst --> Blocks release of ADH and aldosterone --> Diuresis --> Lower blood pressure and plasma volume.
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Section 4

Question Answer
What happens when water is gained but electrolytes are not-ECF volume increases -ECF becomes hypotonic to ICF -fluid shifts from ECF to ICF -may result in overhydration
What are the signs of overhydration Abnormally low Na+ concentrations (hyponatremia). Effects on CNS function (water intoxication).
What does an increase in potassium (K+) in ECF cause -increase aldosterone -K+ secretion in urine - fall in K+ ions
What does parathyroid hormone (PTH) and calcitriol do:raise calcium concentrations in ECF
What does calcitonin do opposes PTH and calcitriol
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Section 5

Question Answer
What are the normal limits of pH in ECF7.35-7.45
How is pH alteredby addition of acids and bases
What do H+ ions do increase acidity.
What are buffers A dissolved compound that can provide or remove H+ ions. Used to stabilise pH.
What are the 3 major buffer systems -carbonic acid bicarbonate buffer -protein buffers -phosphate buffer system
What is the equation for the carbonic acid-bicarbonate buffer system CO2 + H20 <---> H2CO3 <---> H+ + HCO3
How do amino acids work as a protein buffer system if pH rises: in an alkaline medium amino acid acts as an acid and releases H+. If pH falls in acidic medium, amino acid acts as a base and absorbs H+
What is the phosphate buffer system Consists of a weak acid (H2PO4-). Important in buffering pH of ICF.
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Section 6

Question Answer
Describe the buffer system in the body and what occurs where buffer system occurs in ICF and ECF. ICF includes phosphate buffer system and protein buffer system. ECF includes protein buffer system and carbonic acid- bicarbonate buffer system. The protein buffer system includes the Hb buffer system in RBCs, the amino acid buffers (all proteins) and plasma protein buffers,
How is the acid-base balance maintained Combined activities of -Buffer systems (temporarily restores homeostasis) -respiratory mechanisms -renal mechanisms
What is respiratory compensation -Occurs whenever body pH moves outside normal limits -Directly affects carbonic acid–bicarbonate buffer system -Incr respiratory rate lowers PCO2 -Decr respiratory rate increases PCO2
What is renal compensation -Is a change in rates of H+ and HCO3— secretion or reabsorption by kidneys in response to changes in plasma pH. -Kidneys assist lungs by eliminating CO2
*look at carbonic acid-bicarbonate buffer system and plasma pH **Located on pg 34, acid-base balance lecture.
Describe the carbonic acid-bicarbonate buffer system and plasma pH in response to acidosissodium bicarbonate (NaHCO3) goes to Na+ and HCO3-. This bicarbonate ion joins with addition of H+ to make carbonic acid, this is then split into CO2 and H20 and breathed out. Therefore, increased respiratory rate lowers PCO2. The kidneys also generate HCO3- (and vise versa)
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