Renal Review

Question 1

What is the Renin-Angiotensin-Aldosterone System?

Answer 1

1. Macula Densa sense low flow rate into the Glomerulus
2. Macula Densa cells stimulate the Juxtaglomerular cells of the Glomerulus to secrete Renin
3. Renin turns Angiotensinogen (produced by the Liver) into Angiotensin I
4. Angiotensin I is converted by ACE (from lungs) into Angiotensin II
5. Angiotensin II stimulates Aldosterone and ADH release in the Kidneys AND Vasoconstricts to increase BP
6. Aldosterone reabsorbs Na and H2O in the Distal Tubule
7. ADH opens up Aquaporin channels in Collecting Duct and increases H2O reabsorption
8. Increased Filtrate causes negative feedback to shut off Macula Densa cells

Question 2

Where does a majority of Filtration occur in the Kidney?

Answer 2

Renal Cortex

Question 3

In what part of the Nephron does a majority of reabsorption occur?

Answer 3

Proximal Tubule

Question 4

What makes the Distal Tubule different than the Proximal Tubule?

Answer 4

Distal Tubule performs REGULATION as well as Reabsorption while Proximal only performs Reabsorption

Question 5

Where is the one place in the Nephron that has different cell types?

Answer 5

Distal Tubule:

1. Principal Cells (primary)
2. Intercalated Cells (alpha and beta) for Acid/Base balance

Question 6

What is the Juxtaglomerular Apparatus?

Answer 6

Where the Distal Tubule runs right next to the Glomerulus and the Macula Densa cells can sense flow rate into the Glomerulus and stimulate Juxtaglomerular cells to secrete Renin which increases the amount of filtrate

Question 7

What are the types of Nephrons?

Answer 7

1. Outer Cortical (Superficial) Nephron 80%

2. Juxtamedullary (Deep) Nephron 20%

Question 8

Where does blood go after the Efferent Arteriole?

Answer 8

1. Peritubular Capillaries (goes to Cortical Nephron)

2. Vasa Recta (goes to Juxtamedullary Nephron)

Question 9

What does the term “Freely Filtered” mean?

Answer 9

A substance is present in the filtrate at the same concentration as it is in the plasma

Question 10

What is the “Hose Analogy?”

Answer 10

A hose with a bunch of holes in it is a Capillary
A bucket is the Bowman’s Capsule
Water slowly filling the bucket is Filtrate
Substances that freely move into the bucket are “Freely Filtered” substances

Question 11

What is normal Glomerular Filtration Rate (GFR)?

Answer 11

125 mL/min which translates into 180 L/day

(All other capillaries in the body only accomplish 4L/day)

Average Plasma Volume in human is 3L so the kidney filters plasma about 60 times a day

Question 12

What are some examples of Freely Filtered Substances?

Answer 12

1. Ions (ClaNK and Bicarb)
2. Neutral Organics (glucose and urea)
3. Amino Acids
4. Peptides (Insulin and ADH)

Question 13

What is normal Glomerular Filtration Rate (GFR)?

Answer 13

125 mL/min which translates into 180 L/day

Average Plasma Volume in humans is 3L so the kidney filters plasma about 60 times a day

Question 14

What are the different cell types of the Glomerulus? What is their purpose?

Answer 14

1. Podocytes filter by SIZE
2. Endothelial Cells filter by SIZE
3. Mesangial Cells filter by CHARGE

Question 15

What are the 4 forces that play a role in GFR?

Answer 15

1. Surface Area (Kf)
2. Hydrostatic Pressure of the Glomerulus (HPG)
3. Hydrostatic Pressure of the Bowman’s Space (HPBS)
4. Oncotic Pressure of the Glomerulus (piG)

GFR= Kf x NFP OR Kf x [HPG-(HPBS-PiG)]

Question 16

How can Hydrostatic Pressure of the Glomerulus and the GFR be regulated?

Answer 16

Via the Afferent and Efferent Arterioles:
1. Constricting Afferent Arteriole lowers HPG and GFR

2. Constricting Efferent Arteriole raises HPG and GFR
3. Dilating Afferent Arteriole raises HPG and GFR
4. Dilating Efferent Arteriole lowers HPG and GFR

Question 17

How could you significantly raise the Hydrostatic Pressure of the Glomerulus and ultimately the GFR?

Answer 17

By Dilating the Afferent Arteriole and Constricting the Efferent Arteriole

Question 18

What is Splay?

Answer 18

Term for Variability within the body and Heterogeneity of Nephrons that causes Glucose to show up in urine before the Tmax is reached (Glucose Tmax= 320 mg/min

Juxtamedullary Nephrons are longer than Cortical Nephrons so they have more transporters

Question 19

What is the difference between the Descending Loop of Henle and the Ascending Loop of Henle?

Answer 19

1. Descending Loop of Henle is permeable to H2O and impermeable to solutes (NO REABSORPTION)
2. Ascending Loop of Henle is permeable to solutes and impermeable to H2O (Site of Reabsorption)

Question 20

What makes the Apical Membrane transporter in the Ascending Loop of Henle unique?

Answer 20

It moves 4 ions at the same time

1 Na down its gradient
1 K up its gradient
2 Cl down its gradient

Question 21

Talk about the effects of K intake on Aldosterone and Blood Volume:

Answer 21

1. Increased K Intake
2. Increases Plasma K Concentration
3. Increases Aldosterone Secretion
4. Increase in Plasma Aldosterone
5. Aldosterone increases in Na/K ATPase on Basolateral Membrane in the Proximal Tubule and opens gated K channels on the Apical Membrane
6. K Secretion into the Lumen increases which increases the amount of K that is excreted
7. Aldosterone also opens Na gated channels causing an increase in Na reabsorption
8. H2O follows the reabsorbed Na, SO Blood Volume is increased and so is Blood Pressure
9. Lower K in the plasma causes negative feedback decreasing Aldosterone secreted in the blood

Question 22

How are you able to increase ones Blood Volume without decreasing Osmolarity?

Answer 22

Administer Saline solution