Concentration Mechanisms & Urine Formation - Quiz 3

Question 1

Where in the Kidney is Renin made?

Answer 1

Juxtaglomerular Apparatus

Question 2

What are the 4 components of the Juxtaglomerular Apparatus?

Answer 2

Afferent Smooth Muscle Cells

Efferent Smooth Muscle Cells

Extraglomerular Mesangial Cells

Macula Densa Cells

Question 3

What is the most potent vasoconstrictor known?

Answer 3

Angiotensin II

Question 4

What is the Renin Angiotensin Pathway?

Answer 4

1. Renin cleaves Angiotensinogen that came from the Liver to Angiotensin I
2. ACE from the Lungs converts Angiotensin I to Angiotensin II

Question 5

What does Angiotensin II do?

Answer 5

Vasoconstriction

↑Aldosterone Synthesis & Release

↑ADH Release

↑Thirst

Feedback Renin Inhibition

Releases Prostaglandins

Question 6

Along w/ Vasoconstriction, What is the purpose for Angiotensin II to release Prostaglandins?

Answer 6

To maintain GFR even w/ Vasoconstriction

Question 7

How does Angiotensin II affect the Adrenal Gland?

Answer 7

Stimulates it to Release Aldosterone causing Salt & Water Reabsorption

Question 8

What is Aldosterone?

Answer 8

Steroid made in the Zona Glomerulosa of the Adrenal Cortex that acts on the Distal Tubule & Collecting Ducts to Secrete Potassium & Hydrogen Ions, while Reabsorbing Sodium

Question 9

What stimulates the release of Aldosterone?

Answer 9

Angiotensin II

Increased ECF Potassium

Decreased Sodium

Question 10

What is the Atrial Naturetic Peptide?

Answer 10

Hormone made in the Atria that does the opposite of the Angiotensin Pathway by

↓Na Reabsorption

↑GFR

Inhibit Renin, Aldosterone, & ADH

Question 11

What is Conn’s Syndrome?

Answer 11

Aldosterone Secreting Tumor that causes

HTN

Hypernatremia

Hypokalemia

Question 12

What are the Concentrating & Diluting Mechanisms of the Kidney?

Answer 12

ADH

ANP

Countercurrent Multiplier

Urea

Question 13

What dictates the Obligatory Urine Volume?

Answer 13

The max concentrating ability of the kidney - normally 0.5L/day

Question 14

What is ADH?

Answer 14

An Octapeptide made in the Hypothalamus, then Stored & Release by the Posterior Pituitary to Conserve Water by Concentrating Urine

Question 15

How does an increase in ECF Osmolarity affect the Osmoreceptor cells in the Anterior Hypothalamus?

Answer 15

Causes them to Shrink –> sends signal to Posterior Pituitary –> ADH Release

Question 16

Which part of the Kidney does ADH work to Increase Water Permeability?

Answer 16

Late Distal Tubules

Coritcal & Medullary Collecting Ducts

Question 17

What stimulates ADH release?

Answer 17

Osmoreceptors

Mechanoreceptors/Baroreceptors

Angiotensin II

Sympathetic Stimulation

Anesthesia

Nicotine

Question 18

What Inhibits ADH Release?

Answer 18

Alcohol

Clonidine

Haldol

Question 19

What kind of condition must the Interstitium be in for ADH to work?

Answer 19

Hypertonic

Question 20

What is needed to form Concentrated Urine?

Answer 20

High ADH

Hypertonic Renal Medullary Interstitium

Water

Question 21

What are the Key Features of the Kidneys that help it Concentrate Urine?

Answer 21

Henle’s U-Shape - Opposite Flows

Permeability of Certain Nephron Segments

ATP Energy

Question 22

What’s the max amount of urine concentration can the kidney produce?

Answer 22

1200 - 1400 mOsm/L

Question 23

What Increases the Osmolality of the Renal Interstitium?

Answer 23

Active Na & Cl Transport in the TAL

Question 24

What is the Osmotic composition of the Fluid that enters the Descending Limb?

Answer 24

Enters as Iso-Osmotic, but a lot gets absorbed making it more concentrated

Question 25

What are the Major Factors that contribute to the Hyperosmolarity of the Medullary Interstitium?

Answer 25

• Active Transport of Sodium & Co-Transport of Potassium & Chloride out the TAL
• Active Transport of ions out the Collecting Ducts
• Facilitated Diffusion of Urea out the Medullary Collecting Ducts
• Diffusion of a bit of water out the Medullary Tubules

Question 26

How is the High Medullary Interstium Osmolarity preserved in the presence of ADH?

Answer 26

The Large amount of water is reabsorbed into the Renal Cortex rather than the Renal Medulla

Question 27

Why is the Osmotic Gradient the most within the Inner Medulla even though the TAL is located in the Outer Medulla?

Answer 27

Urea

Question 28

What is Urea?

Answer 28

Byproduct of amino acid metabolism produced by the liver at 25-30 g/day

Question 29

What is the role of Urea?

Answer 29

Accounts for 40-50% of Renal Interstitium Osmolarity

Question 30

How does Urea get into the Renal Interstitium?

Answer 30

Permeable in the Inner Medulla only w/ ADH and diffuses to the Interstitium and gets trapped there.

Question 31

Where in the Kidney is some Urea Permeable w/o ADH?

Answer 31

Thin Ascending Loop

Question 32

What is the Role of the Vasa Recta?

Answer 32

Preserve Medullary Hyperosmolarity by

Removing reabsorbed fluid from Interstitium

&

Minimizing Solute Uptake from Medulla

Question 33

What is the Solute & Fluid movement in the Descending Vasa Recta?

Answer 33

Rapid Flow = More Fluid Leaving than Solute Entering

Question 34

What is the Solute & Fluid movement in the Ascending Vasa Recta?

Answer 34

Decreased Hydrostatic Pressure & Increased Blood Osmolality

More Solute Entering than Fluid Leaving

Question 35

What conditions might affect the ability to Concentrate Urine?

Answer 35

Too much or Too Little ADH

Impaired Countercurrent Mechanism

Inability of Distal Tubule, Collecting Tubule, & Collecting duct to Respond to ADH

Question 36

What is Central Diabetes Insipidus?

Answer 36

Failure to Produce ADH

Question 37

What is the treatment for Central Diabetes Insipidus?

Answer 37

Desmopressin - DDAVP

Acts on V₂ Receptors to increase Water permeability in the Late Distal & Collecting Tubules

Question 38

What is Nephrogenic Diabetes Insipidus?

Answer 38

Inability of Renal Tubular Segments to respond to ADH