Physiology of the urinary system 53 what is the

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Physiology of the Urinary System 53. What is the hormonal control mechanism for the renal flow? RAA (responds when body’s blood pressure drops too low; helps reabsorption of more NA+ & H2O from the filtration) REVIEW DIAGRAM
54. Angiotensinogen is a pre-enzyme produced by the ___ and freely circulates in the blood. Liver
55. When blood pressure drops, the enzyme ____ is released by the juxtaglomerular (JG) cells of the nephron. Renin
56. In the ____, angiotensin I is converted to ____. Lungs, Angiotensin II
57. Once circulating angiotensin II reaches the adrenal cortex, it causes the release of the hormone ____. Aldosterone
58. What is reabsorption? Fluid and substances moving from filtrate back into blood.
59. True or false: all reabsorption occurs in the renal tubules by diffusion. False (some ions require active transport)
60. Where does the greatest amount of renal tubular reabsorption occur? In cells of the PCT
61. About what percentage of Na+ is reabsorbed in the PCT? The loop of Henle? The DCT? 65%, 25%, 10% (DCT reclaims nearly all when necessary)
62. What is secretion? I nvolves substances entering the filtrate from the surrounding fluid, allowing for the elimination of undesirable substances, such as urea.
63. What is countercurrent flow? Movement of fluids in opposite directions through adjacent channels.
64. When an osmotic gradient is isosmotic, what does this mean? T he fluid outside and inside have the same osmotic concentrations,
65. What is the concentration of the filtrate in the PCT vs. the bottom of the loop of Henle? 300 mOsm/L, 1200 mOsm/L
66. True or False: The descending and ascending regions of the loop of Henle have the same reabsorption
67. True or False: The concentration of urea is relatively low in the distal convoluted tubule and the cortex regions of the
68. ADH is secreted by the ____. Posterior Pituitary Gland
69. True or False: ADH increases water output. FALSE
70. Describe the action of ADH. ADH inhibits urine output by increasing the number of channels in the cells of the collecting ducts. Increasing the channels allows water to pass easily from the filtrate and move into the surrounding interstitial space, eventually returning to blood circulation. Water rapidly leaves the filtrate through the channels in the collecting ducts opened by ADH. ADH retains up to 99% of water in filtrate, and kidneys excrete very small volume of highly concentrated urine.
71. Describe the mechanisms of aldosterone. Aldosterone increases Na+ reabsorption through the excretion of hydrogen ions (H+). Sodium ions are pumped out of the filtrate while hydrogen ions are pumped inside for excretion. Because water follows salt, Na+ reabsorption also causes water reabsorption. A second action of aldosterone is to increase potassium secretion through sodium-potassium pumps. Na+ is pumped out of the filtrate to be returned to the blood while K+ is excreted in urine.
72. What are diuretics?

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