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Renal 4 & 5
Urine Dilution & Concentration, Ions
51
Physiology
Undergraduate 4
11/21/2016

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Cards

Term
Where do selective changes in tubular filtrate occur?
Definition
loop of henle, some in DT
Term
3 Main mechanisms that alter urine concentration
Definition
-hypotonic medullary interstitium
-dilution of tubular fluid in ascending LoH & distal tubule
-collecting ducts selectively permeable to water in response to ADH/vasopressin
Term
What structure removes water from the medullary interstitium?
Definition
vasa recta
Term
What portion of the LoH is impermeable to water?
Definition
ascending limb
Term
If salt concentration in the tubule is decreasing, while the concentration in the blood increases, what portion of the loop of henle are we in>
Definition
ascending
Term
If salt concentration in the tubule is increasing, while the concentration in the blood decreases, what portion of the loop of henle are we in>
Definition
descending
Term
What region of the Loop of Henle is considered the 'diluting' segment?
Definition
ascending - Na is pumped out in to the interstitium leaving water in the tubule
Term
Is reabsorption of salt in the ascending loop of henle active or passive?
Definition
active - uses Na/K/2CL co transporters to drive salt out
Term
What role does ADH play in the collecting duct?
Definition
regulates aquaporin activity to produce dilate or concentrated urine (makes them more permeable to water to promote reabsorption)
Term
What does aldosterone do & where does it act?
Definition
enhances reabsorption of Na+ and secretion of K+ in the collecting ducts
Term
How does vasopressin / ADH work?
Definition
1. Vasopressin binds to mmb receptor
2. cAMP messenger pathway activated
3. AQP2 water pores inserted into mmb
4. Water reasborbed by osmosis into the blood
Term
What is isothenuria?
Definition
urine osmolality is equal to plasma osmolality
Term
What is hyposthenuria?
Definition
urine osmolality is lower than plasma osmolality
Term
What is pressure natriuresis
Definition
Changes in blood pressure within the kidney's vascular system when directly alters Na+ excretion
Term
How does the body sense/respond to changes in water or fluid volunme?
Definition
Pressure natriuresis

AND

Sensors in body that detect changes in BP & osmolarity, and will lead to secretion of hormones that regulate Na+ levels
Term
What hormone drives thirst?
Definition
ADH (vasopressin)
Term
In regulating body fluid, osmoreceptors will detect changes in blood solute concentration and direct the secretion of _____ to target the urinary H2O and H2O intake (thirst) systems.
Definition
ADH (vasopressin)
Term
How is the hypothalamus involved in regulating plasma and ECF osmolality?
Definition
1. Changes in osmolality trigger changes in size of chemoreceptor neurons in hypothalamus

2. Shrinking of cells increases ADH release

3. ADH increases water reabsorption in kidney, stimulates thirst
Term
Where is vasopressin/ADH secreted from?
Definition
posterior pituitary
Term
Where are low-pressure mechanopreceptors found?
Definition
cardiac atria & pulmonary vessels
Term
What causes antrial natriuretic peptide to be released? What is it's general role?
Definition
Increase in blood pressure/blood volume in the cardiac atria & pulmonary vessels

-promotes elimination of Na+ (and subsequently water) to reduce blood volume
Term
ANP directly decreases the secretion of...
Definition
renin & aldosterone
Term
What does ANP do? (4)
Definition
-dilates afferent glomerular arteriole, constricts efferent

-decreases Na reabsorption in DCT & collecting duct

-increases blood flow through vasa recta (decreases osmolarity of medullary interstitium)
-leads to increased fluid secretion

-decreases secretion of renin & aldosterone
Term
What hormone is secreted in response to an increase in blood pressure?
Definition
ANP
Term
What hormone is initially secreted in response to a decrease in blood pressure?
Definition
renin
Term
What does renin do? (5)
Definition
-decrease perfusion pressure in the justaglomerular apparatus
-increase activity of carotid pressure sensors
-decrease NaCl delivery to macula densa cells
-increases angiotensin levels = increased aldosterone secretion
-promotes more ADH secretion
Term
Where does angiotensin II act?
Definition
proximal tubule
Term
Where does aldosterone act?
Definition
distal tubules & collecting ducts
Term
In the proximal tubule, ______ stimulates Na+/K+ ATPase while _____ and ______ stimulate Na+/H+ exhangers in the luminal membrane
Definition
norepinephrine

angiotensin II & norepinephrine
Term
What region of the adrenal cortex produces aldosterone?
Definition
zona glomerulosa
Term
Aldosterine is part of the _____ family
Definition
mineralcorticoid
Term
What does aldosterone do?
Definition
promotes reabsorption of Na+ and water in the distal tubules & collecting ducts to increase blood volume & pressure

Also promotes secretion of potassium
Term
Where are high-pressure baroreceptors found? What do they do?
Definition
aortic arch & carotid sinus

-change autonomic outflow to influence blood pressure
Term
What are the 3 'sensors' of blood volume or pressure?
Definition
Low-pressure mechanoreceptors (volume)
High-pressure baroreceptors (pressure)
JG cells of kidney
Term
How is potassium regulated in the body?
Definition
-move back and forth between extracellular and intracellular compartment

-Potassium loading (rapid uptake by cells to prevent increase in plasma concentrations), then release slowly later on
Term
What hormones shift K+ in to cells?
Definition
Epinephrine
Insulin
Aldosterone
Term
Acidosis causes an (increase/decrease) in plasma K+
Definition
increase
Term
What is rhabdomyolysis?
Definition
cell lysis resulting in a release of K+ into the extracellular compartment (tying up)
Term
70% of K+ is reabsorbed in the ____ and another 20% in the _____
Definition
proximal convoluted tubule

ascending LoH
Term
K+ secretion occurs primarily in....
Definition
the DCT & K+ channels
Term
What effect does aldosterone have on K+ update?
Definition
decreases K+ update
Term
How does sodium get transported into DCT & collecting ducts?
Definition
Na-K-ATPase
Term
How is potassium excretion regulated?
Definition
1. High K+ = increased aldosterone secretion = increased K+ secreton

2. High K+ = direct stimulation of K+ secretion by tubular cells

3. Increased tubular flow = lower K+ concentration = increased K+ secretion
Term
What test is used to asses GFR, and what does it tell us?
Definition
BUN/creatinine/inulin clearance

High plasma concentration indicates low GFR
Term
What test is used to assess tubular function and what does it tell us?
Definition
specific gravity of urine

Poor concentrating ability indicates problem with tubular function
Term
What test is used to assess electrolyte regulation and what does it tell us?
Definition
Abnormal Na+, K+ levels

Abnormal levels indicate a problem with GFR or tubular reabsorption
Term
What test is used to assess water balance and what does it tell us?
Definition
dehydration

indicates inability to concentrate urine (can't reabsorb water properly)
Term
What test is used to assess erythropoietin production and what does it tell us?
Definition
anemia

indicates inability of JG cells to produce EPI
Term
What is hyperphosphatemia?
Definition
increase in phosphate in the blood, indicating a decrease in GFR
Term
Why is Vit D metabolism important?
Definition
Vit D regulates calcium levels in the blood
Term
Anemia may indicate a problem with what part of the kidney?
Definition
juxtaglomerular cells
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