Concentrating Mechanisms and Urine Formation Flashcards
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.
macula densa
calcium
constriction
renin
_______is a protein enzyme released by the kidneys when BP is too low
Renin
Site of renin synthesis:
The Juxtaglomerular Apparatus
The JGA consists of 4 components:
- Smooth muscle cells in the afferent arteriole
- Smooth muscle cells in efferent arteriole
- Extraglomerular mesangial cells
- Macula dense cells in the Distal Tubule
The ______ ______is a collection of specialized epithelial cells in the high cortical _____ and ____ that detect sodium concentration of the fluid in the tubule.
macula densa
TAL and DCT
The Juxtaglomerular Apparatus: Main function–>
regulate blood pressure and the filtration rate of the glomerulus.
Most potent vasoconstrictor known =
Angiotensin II
Renin causes ________to be cleaved to _______.
angiotensinogen
angiotensin I
Actions of Angiotensin II:
Vasoconstriction and increased BP
Increased aldosterone
Increased ADH (antidiuretic hormone)
Increased thirst
Feedback inhibition of renin release (slow process down)
Although AgII constricts both afferent and efferent arterioles it releases ______ which act to maintain ____ despite its constrictive effects.
prostaglandins
GFR
The function of________ is to cause marked increase in sodium reabsorption by the kidney tubules, thus increasing the total body extracellular fluid sodium.
aldosterone
Stimulation for aldosterone release:
Increased K+ levels in the ECF (will waste K+)
Angiotensin II
Decreased Na+ levels
The final common pathway in a complex response to decreased effective arterial volume:
Aldosterone
Aldosterone acts on the ______ and ______ ______ to cause ____ and ___ secretion in exchange for Na+
distal tubule and collecting ducts
K+ and H+
Net effect is to get rid of K+ and H+
Aldosterone helps control blood pressure by……
holding onto salt and losing potassium from the blood.
Conn’s syndrome:
Aldosterone secreting tumor causes hypertension, hypernatremia, and hypokalemia
Renal Concentrating and Diluting Mechanisms:
ADH
ANP (gets rid of water)
Countercurrent multiplier
Role of Urea
Dictated by the maximum concentrating ability of the kidney:
Obligatory Urine Volume
A normal 70 kg human must excrete ____ mOsm of solute each day…..Assuming a maximum urine concentrating ability of 1200 mOsm/L
600
Obligatory Urine Volume
600 mOsm/Day / 1200 mOsm/L
= 0.5 L/Day
Plays a major role in conserving water by concentrating urine.
Antidiuretic hormone (ADH)
Octapeptide, synthesized in hypothalamus
Stored and released in the posterior pituitary
ADH enters the blood stream and is transported to the kidneys, where it increases the water permeability of the…..
late distal tubules, cortical collecting tubules, and medullary collecting ducts
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.
hypothalamus
atria and aorta
________inhibits ADH release!
Alcohol
Vasopressin functions:
-decreases urine production
-decrease sweating
-increase BP
Dehydration =
ADH released!
Overhydration =
ADH inhibited!
In the absence of ADH, the collecting system is relatively impermeable to water leading to….
decreased water conservation and a dilute urine
The basic requirements for forming a concentrated urine are:
High ADH
High osmolarity of the renalmedullary interstitial fluid
Anatomy of MedullaryCountercurrent Multiplier System:
Juxta-medullary nephrons with long loops of Henle & vasa recta peritubular capillaries reach into medulla.
The______ _______ has a high concentration of urea.
This plays an important role in generating a ______ _______.
medullary interstitium
hypertonic interstitium
The TAL is in the outer medulla, but the osmotic gradient is maximal in the inner medulla
How does this work?
UREA
How does the medullary interstitium generate such a high urea concentration?
The TAL is impermeable to water and urea.
______contributes 40% of the osmolarity of renal medulla gradient during max urine concentration
Urea
When does Urea passively diffuse from medullar collecting duct?
During water deficits when ADH present
2 functions of the Vasa Recta:
Remove reabsorbed fluid from the interstitium
Minimize solute uptake from the medulla
The treatment for central diabetes insipidus is administration of a synthetic analog of _____,______which acts selectively on ___receptors to increase water permeability in the……
ADH,desmopressin,
V2
late distal and collecting tubules
What is “Nephrogenic” Diabetes Insipidus
Normal or elevated levels of ADH are present but therenal tubular segments cannot respond appropriately.
The abnormality resides in the kidneys.
