7.6 • Define gel electrophoresis. Briefly, describe how it works. Water Balance
Body adjusts for increased water intake by increasing _____________ output. • Adjustments involve the nervous and endocrine systems.
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.
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.
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
ADH: makes upper part of distal tubule permeable to water • High [NaCl] in intercellular spaces osmotic pressure increases water sucked out of nephron.
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.
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.
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+.
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.
Seatwork/Homework • Page 356, # 1-8, 10.