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Water Balance PowerPoint Presentation
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Water Balance

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Water Balance

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  1. 7.6 • Define gel electrophoresis. Briefly, describe how it works. Water Balance

  2. Body adjusts for increased water intake by increasing _____________ output. • Adjustments involve the nervous and endocrine systems.

  3. Regulating ADH – chemical response • ADH: antidiuretic hormone – causes kidneys to increase water reabsorption. • ADH: produced by specialized nerve cells in the hypothalamus. • Pituitary gland: stores and releases ADH into blood. • Osmoreceptors: specialized nerve receptors in the hypothalamus.  when blood solutes become more concentrated, increases blood’s osmotic pressure  osmoreceptors shrink (losing water)  nerve message sent to pituitary gland  ADH released into blood  reabsorbs more water from the nephrons  osmotic pressure regulated.

  4. Regulating ADH – behavioural response • Shrunken osmoreceptors pituitary releases ADH  initiates thirst  water consumed  concentration of blood solutes decrease  lower osmotic pressure  fluids from blood to osmoreceptors  swell  nerve signal to nephrons  less water reabsorbed.

  5. ADH & the NEPHRON • Proximal tubule very permeable to water (85% of reabsorption occurs here). Descending loop of Henleis also permeable to water and ions. • Ascending loop of Henle and distal tubule is impermeable to water without ADH. • Permeable to NaCl active transport of Na+ ions causes increase in ions in medulla (interstitual fluid). • 15% of water filtered into nephron will be lost in urine if no ADH present

  6. ADH: makes upper part of distal tubule permeable to water • High [NaCl] in intercellular spaces  osmotic pressure increases  water sucked out of nephron.

  7. Kidneys and Blood Pressure • Kidneys adjust blood volumes  adjusts blood pressure. • Aldosterone: hormone that increases Na+ reabsorption. • Produced in the cortex or adrenal glands (right above kidneys). • As NaClreabsorption increases, osmotic gradient increases  more water moves out of nephrons by osmosis.

  8. Decrease in blood pressure • Reduction of oxygen and nutrients to tissues. • Juxtaglomerular apparatus: (near glomerulus)  detects low blood pressure  releases renin (enzyme that converts angiotensinogen to angiostensin) • Angiostensin: enzyme • Constriction of blood vessels  increase in blood pressure. • Stimulates the release of aldosterone from adrenal gland.

  9. pH Balance • Kidneys maintain pH balance • Relatively constant: b/n 7.3 & 7.4 • We eat acidic/basic foods • Cellular respiration: CO2 production. • Carbonic acid, weak acid, is produced. • Buffer system: bicarbonate ion eliminates extra H+.

  10. Buffer system • Kidneys help restore buffer. • CO2 actively transported from peritubular capillaries (surround the ______________) into cells surrounding the nephron • CO2 + H2O  HCO3- and N+ ions. • HCO3- back into blood. • H+ recombind with phosphate ions or ammonia  excreted in urine.

  11. Very Vague Summary...

  12. Seatwork/Homework • Page 356, # 1-8, 10.