Concentrating Mechanisms and Urine Formation

Question 1

Increased renal arterial pressure increases the delivery of fluid and sodium to the _____ ______. ATP is released and _______increases in granular and smooth muscle cells of the afferent arteriole, causing arteriole _____ and decreased ______release.

Answer 1

macula densa
calcium
constriction
renin

Question 2

_______is a protein enzyme released by the kidneys when BP is too low

Answer 2

Renin

Question 3

Site of renin synthesis:

Answer 3

The Juxtaglomerular Apparatus

Question 4

The JGA consists of 4 components:

Answer 4

1. Smooth muscle cells in the afferent arteriole
2. Smooth muscle cells in efferent arteriole
3. Extraglomerular mesangial cells
4. Macula dense cells in the Distal Tubule

Question 5

The ______ ______is a collection of specialized epithelial cells in the high cortical _____ and ____ that detect sodium concentration of the fluid in the tubule.

Answer 5

macula densa
TAL and DCT

Question 6

The Juxtaglomerular Apparatus: Main function–>

Answer 6

regulate blood pressure and the filtration rate of the glomerulus.

Question 7

Most potent vasoconstrictor known =

Answer 7

Angiotensin II

Question 8

Renin causes ________to be cleaved to _______.

Answer 8

angiotensinogen
angiotensin I

Question 9

Actions of Angiotensin II:

Answer 9

Vasoconstriction and increased BP
Increased aldosterone
Increased ADH (antidiuretic hormone)
Increased thirst
Feedback inhibition of renin release (slow process down)

Question 10

Although AgII constricts both afferent and efferent arterioles it releases ______ which act to maintain ____ despite its constrictive effects.

Answer 10

prostaglandins
GFR

Question 11

The function of________ is to cause marked increase in sodium reabsorption by the kidney tubules, thus increasing the total body extracellular fluid sodium.

Answer 11

aldosterone

Question 12

Stimulation for aldosterone release:

Answer 12

Increased K+ levels in the ECF (will waste K+)
Angiotensin II
Decreased Na+ levels

Question 13

The final common pathway in a complex response to decreased effective arterial volume:

Answer 13

Aldosterone

Question 14

Aldosterone acts on the ______ and ______ ______ to cause ____ and ___ secretion in exchange for Na+

Answer 14

distal tubule and collecting ducts
K+ and H+

Net effect is to get rid of K+ and H+

Question 15

Aldosterone helps control blood pressure by……

Answer 15

holding onto salt and losing potassium from the blood.

Question 16

Conn’s syndrome:

Answer 16

Aldosterone secreting tumor causes hypertension, hypernatremia, and hypokalemia

Question 17

Renal Concentrating and Diluting Mechanisms:

Answer 17

ADH
ANP (gets rid of water)
Countercurrent multiplier
Role of Urea

Question 18

Dictated by the maximum concentrating ability of the kidney:

Answer 18

Obligatory Urine Volume

Question 19

A normal 70 kg human must excrete ____ mOsm of solute each day…..Assuming a maximum urine concentrating ability of 1200 mOsm/L

Answer 19

600

Question 20

Obligatory Urine Volume

Answer 20

600 mOsm/Day / 1200 mOsm/L
= 0.5 L/Day

Question 21

Plays a major role in conserving water by concentrating urine.

Answer 21

Antidiuretic hormone (ADH)

Octapeptide, synthesized in hypothalamus
Stored and released in the posterior pituitary

Question 22

ADH enters the blood stream and is transported to the kidneys, where it increases the water permeability of the…..

Answer 22

late distal tubules, cortical collecting tubules, and medullary collecting ducts

Question 23

ADH:
Osmoreceptors in the________respond to effective ECF osmolality, (increased osmolality stimulates release).

Mechanoreceptors in the____ and ____will detect decreases in volume and stimulate ADH release.

Answer 23

hypothalamus
atria and aorta

Question 24

________inhibits ADH release!

Answer 24

Alcohol

Question 25

Vasopressin functions:

Answer 25

-decreases urine production
-decrease sweating
-increase BP

Question 26

Dehydration =

Answer 26

ADH released!

Question 27

Overhydration =

Answer 27

ADH inhibited!

Question 28

In the absence of ADH, the collecting system is relatively impermeable to water leading to….

Answer 28

decreased water conservation and a dilute urine

Question 29

The basic requirements for forming a concentrated urine are:

Answer 29

High ADH
High osmolarity of the renalmedullary interstitial fluid

Question 30

Anatomy of MedullaryCountercurrent Multiplier System:

Answer 30

Juxta-medullary nephrons with long loops of Henle & vasa recta peritubular capillaries reach into medulla.

Question 31

The______ _______ has a high concentration of urea.
This plays an important role in generating a ______ _______.

Answer 31

medullary interstitium
hypertonic interstitium

Question 32

The TAL is in the outer medulla, but the osmotic gradient is maximal in the inner medulla
How does this work?

Answer 32

UREA

Question 33

How does the medullary interstitium generate such a high urea concentration?

Answer 33

The TAL is impermeable to water and urea.

Question 34

______contributes 40% of the osmolarity of renal medulla gradient during max urine concentration

Answer 34

Urea

Question 35

When does Urea passively diffuse from medullar collecting duct?

Answer 35

During water deficits when ADH present

Question 36

2 functions of the Vasa Recta:

Answer 36

Remove reabsorbed fluid from the interstitium
Minimize solute uptake from the medulla

Question 37

The treatment for central diabetes insipidus is administration of a synthetic analog of _____,______which acts selectively on ___receptors to increase water perme­ability in the……

Answer 37

ADH,desmopressin,
V2
late distal and collecting tubules

Question 38

What is “Neph­rogenic” Diabetes Insipidus

Answer 38

Normal or elevated levels of ADH are present but therenal tubular segments cannot respond appropriately.
The abnormality resides in the kidneys.