chapter 24: urinary system

Question 1

what are the 2 primary components of the juxtaglomerular apparatus? how are they stimulated and what substance is released in response?

Answer 1

granular cells and the macula densa: granular cells contract when stimulated by strech, and synthesize, store and release renin; the macula densa detect changes in [NaCl], and signal granular cells to release renin

Question 2

the juxtaglomerular apparatus also has __________________ cells that communicate with other cells via gap junctions

Answer 2

extraglomerular mesangial

Question 3

what are the 3 layers of the filtration membrane?

Answer 3

glomerular endothelium, glomerular basement membrane, visceral layer of glomerular capsule

Question 4

the ___________ is fenestrated and blocks large structures, such as ___________

Answer 4

glomerular endothelium; formed elements

Question 5

what does the glomerular basement membrane block?

Answer 5

everything but the smallest plasma proteins

Question 6

the ______ layer of the ____________ blocks passage of most _______ proteins

Answer 6

visceral; glomerular capsule; small

Question 7

renal regulation ____________ GFR. if BP↓, afferent arteriole _______________, allowing blood ________ the glomerulus. if BP↑, the afferent arteriole ________________, allowing blood __________ the glomerulus

Answer 7

maintains; vasodilates, into; vasoconstricts, out of

Question 8

direct stimulation by the sympathetic division _____________ GFR, causing ________________ to ____________ blood flow in the glomerulus and renin release w/ subsequent angiotensin II production and ____________ of mesangial cells, _____________ surface area of the filtration membrane

Answer 8

decreasing; vasoconstriction; decrease; contraction; decreasing

Question 9

ANP ____________ GFR through _________________ which _____________ blood flow in the glomerulus. it ____________ renin release and causes ____________ of mesangial cells = __________ surface area.

Answer 9

increases; vasodilation; increases; inhibits; relaxation; increased

Question 10

glomerular hydrostatic pressure (HPg) is the __________ force; blood colloid osmotic pressure (OPg) and capsular hydrostatic pressure (HPc) are the _____________ forces

Answer 10

driving; opposing

Question 11

what is the value of the NFP if HPg is 65 mmHg, OPg is 30 mmHg, and HPc is 20 mmHg?

Answer 11

15 mmHg

Question 12

if HPg increases, what is the effect on NFP? what is the relationship between HPg and NFP?

Answer 12

HPg and NFP have a direct relationship. If HPg increases, NFP will also increase and vice versa

Question 13

how is aldosterone involved in Na+ reabsorption?

Answer 13

• ↑ reabsorption by entering principle cells and binding to intracellular receptors
• increases the number of Na+ channels and Na+/K+ pumps = faster transport
• when Na+ moves into the blood, water follows by osmosis through aquaporins
• K+ increases in tubular fluid

Question 14

what effect does ANP have on sodium reabsorption?

Answer 14

ANP ↓ reabsorption by inhibiting aldo release which means more Na+ and water is excreted in the urine (↑ GFR = ↑ urine output)

Question 15

what 2 hormones are involved in water reabsorption?

Answer 15

• aldosterone increases Na+ transport, meaning water will follow by osmosis via aquaporins
• ADH binds to receptors on principle cells, increases the number of aquaporins = more water reabsorption

Question 16

how is potassium reabsorbed and secreted?

Answer 16

• Na+ leaves tubular fluid (+ water), increasing the [solute] in the fluid
• this sets up a concentration gradient
• solutes move passively out of TF and into blood
• K+ secretion is dependent on aldo levels; increased blood K+ = increased aldo = increased K+ secretion into urine

Question 17

how does PTH affect absorption of PO4 3- and Ca2+?

Answer 17

PTH is released in response to decreased blood Ca2+. it inhibits PO4 3- reabsorption in the PCT and stimulates Ca2+ reabsorption in the DCT; less PO4 3- in blood to make calcium phosphate = less bone deposition = increased blood Ca2+

Question 18

how is the movement of H+ and HCO3- regulated by type A and type B intercalated cells?

Answer 18

type A secrete H+ and reabsorb newly formed HCO3- (blood pH ↑, urine pH ↓)
type B secrete HCO3- and rebsorb H+ (blood pH ↓, urine pH ↑)

Question 19

what happens in the countercurrent multiplier?

Answer 19

in the decending limb, water is permeable and solutes are impermeable = more concentrated
in the ascending limb, solutes are permeable and water is impermeable = less concentrated

Question 20

what is the countercurrent exchange in the vasa recta?

Answer 20

it runs alongside the nephron loop. they perform the opposite actions - beside the ascending limb, water is permeable and solutes are impermeable. beside the descending limb, water im impermeable and solutes are permeable

Question 21

how is dilute urine formed?

Answer 21

more water > decreased osmolality (more dilute) > decreased ADH > decreased aquaporins > decreased water reabsorption > large volume of dilute, pale urine

Question 22

how is concentration urine formed?

Answer 22

less water > increased osmolality (more concentrated) > increased ADH > increased aquaporins > increased water reabsorption > small volume of concentrated, dark urine