Glomerular Filtration and Renal Clearance - Ch 16

Question 1

What hormones does the kidney produce / convert?

Answer 1

Erythropoietin
Renin
1,25-dihydroxyvitamin D (convert to active form)

Question 2

What can the kidney produce during starvation and how?

Answer 2

Glucose (via gluconeogenesis)

Question 3

What percent of the cardiac output enters the kidney? What volume of blood is this?

Answer 3

20% (1 L / min)

Question 4

What is the ratio of cortical (superficial) to juxtamedullary (deep) nephrons?

Answer 4

85% Cortical - 15% Juxtamedullary

Question 5

What do the efferent arterioles associated with the cortical and juxtaglomerular nephrons lead to, respectively?

Answer 5

Cortical - peritubular capillaries (collect material reabsorbed from nephrons)
Juxtaglomerular - vasa recta (collect material reabsorbed from medullary tubules)

Question 6

What is the juxtaglomerular apparatus?

Answer 6

Specialized site where the macula densa is in contact with the distal convoluted tube and afferent arteriole

Question 7

What do the macula densa cells regulate?

Answer 7

Glomerular filtration rate (GFR)

Renin release

Question 8

What are the consequences of damage to the glomerular basement membrane?

Answer 8

Reduce the negative charge and allow large proteins (ie albumin) to be filtered

Question 9

What is the consequence of mesangial matrix deposition?

Answer 9

Decrease area of filtration and reduced renal function

Question 10

What are the symptoms of acute glomerulonephritis?

Answer 10

Edema
Low urine volume
Headaches
Nausea
Joint pain

Question 11

How do you calculate renal plasma flow?

Answer 11

RPF = RBF x (1 - HCT)

Question 12

What is used to determine effective renal plasma flow (ERPF)

Answer 12

Para-aminohippurate (PAH)

Question 13

What is the effective pore size of the glomerulus?

Answer 13

30 A

Question 14

How do you calculate net filtration pressure?

Answer 14

(HP gc - HP bs) - pi gc

Question 15

What is a normal GFR?

Answer 15

100-125 mL/min

130 ml/min (Rao)

Question 16

What is the filtration fraction and how do you calculate it?

Answer 16

The proportion of the RPF that becomes glomerular filtrate

FF = GFR / RPF

Question 17

What is filtered load and how do you calculate it?

Answer 17

Amount of a specific substance filtered per unit time

FLx = Px x GFR

Question 18

What is urinary excretion and how do you calculate it?

Answer 18

The urine concentration of the substance times the volume of urine produced per unit time
Ex = Ux x V

Question 19

How do you calculate reabsorption rate?

Answer 19

Rx = FLx - Ex

Question 20

How do you calculate secretion rate?

Answer 20

Sx = Ex - FLx

Question 21

What is renal clearance and how do you calculate it?

Answer 21

Volume of plasma cleared of a substance per unit time

Cx = (Ux x V) / Px

Question 22

When does clearance equal GFR?

Answer 22

When a substance is freely filtered, but not reabsorbed or secreted

Question 23

What is the relationship between plasma creatinine and GFR?

Answer 23

Proportional to 1 / mg% Pcr

ie 1 = 100%, 2 = 50%, etc

Question 24

What is the mechanism by which arteries and arterioles respond directly to increases in systemic blood pressure?

Answer 24

Mycogenic mechanism

Question 25

What mechanism involves the juxtaglomerular apparatus?

Answer 25

Tubuloglomerular feedback (TGF)

Question 26

What triggers the TGF?

Answer 26

Decrease in flow and tubular sodium leads to decreased arteriolar resistance and increased GFR and vice versa

Question 27

How is the renin-angiotensin-aldosterone system (RAAS) activated?

Answer 27

Low renal vascular flow

Question 28

What is angiotensin II and what does it do?

Answer 28

It is a vasoconstrictor that acts on the renal arteries (decreases GFR)

Question 29

What is atrial natriuretic peptide (ANP) and what does it do?

Answer 29

It is released from the right cardiac atrial myocytes in response to stretch (high blood volume) and increases GFR by dilating the afferent arteriole and constricting the efferent arteriole

Question 30

What stimulates sympathetic nerves and catecholamine secretion and what do they do?

Answer 30

Reductions in systemic blood pressure cause vasoconstriction of the renal arteries and arterioles

Question 31

Name 2 intrarenal prostaglandins and their actions

Answer 31

PGE2 and PGI2 (prostacyclin) are vasodilators

*Note NSAIDS restrict compensatory renal vasodilation