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36 Cards in this Set

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a hairpin-shaped segment of nephron between proximal convoluted tubule (PCT) and distal convoluted tubule (DCT) is the...
Loop of Henle
The lower part of the ____ has thin walls and is permeable to ions
Lower Ascending Limb
has thick walls and actively transports ions OUT of tubule and into the interstitial fluid (I.F.).
Upper ascending limb
Explain how the Na+ pump in 'thick ascending limb actively transorts from tubular cell wall to Interstitial fluid.
- More complex than typical Na pump: 1 Na+, 1 K+ and 2 Cl- pumped together from tubular fluid into cells of wall; Na + pumped from cell to I.F., Cl- follows passively. Excess K+ and Cl- diffuse from cell back into tubule or into I.F.
What part of the kidney is important for setting up osmotic conditions in medulla?
Loop of Henle
What part of the kidney sets up MASSIVE concentration gradient in I.F.?
Loop of Henle
is there a large difference in the concentration of the fluid going in and coming out of the Loop of Henle?
NO, concentration of the fluid going in and coming out of the loop is not terribly different even though the I.F. has a large concentration gradient.
What is the purpose of of creating a large concentration gradient?
This concn. gradient is critical to kidney’s ability to produce concentrated urine.
From blood->Tubule is (secretion/reabsorption)
secretion
From Tubule->Blood is (secretion/reabsorption)
reabsorbtion
What are the two main functions of Distal convoluted Tubule(DCT)?
- Adjust pH of blood (which adjusts pH of urine)
- Adjust ion balance by exchanging Na+ and K+
______ is a steroid hormone from adrenal gland (adrenal cortex). secreted in response to:high blood K+ (moves K out of blood, into urine)
-low blood Na+ (conserves Na, prevents loss in urine)
-and reduced blood volume or pressure: Na is main ion in blood, if level of Na can be increased, will tend to pull water from other compartments, raise volume & pressure
Aldosterone
In DCT, Na/K exchange regulated by the hormone....
aldosterone
Where do most of the pH adjustments occur in nephron?
DCT
The countercurrent multiplier in the nephron in...
Loop of Henle
What is a countercurrent exchanger? What extra feature does a countercurrent multiplier add?
any structure or device that passes two flows alongside each other in opposite directions (hence “countercurrent) and allows diffusion between the flows.

-With the multiplier, countercurrent flows are directly connected at one end, the flow from one stream makes a 180 degree turn and becomes the other stream. This tends to cause whatever is exchanged to be trapped and built up to high levels at the hairpin-turn end.
Explain why the Loop of Henle sets up a large concentration gradient at the bottom of loop of Henle.
Since the descending limb is perm. to water, water will move out of the descending limb by osmosis, but it is imperm. to ions, so ions will be left behind and will make the fluid in the descending limb more concentrated. But because the ions are actively being pumped out of the ascending limb, the fluid that comes out of the top of the ascending limb is actually less concentrated than the fluid coming into the loop.
Collecting duct uses concentration gradient to adjust urine ______ and __________.
Collecting duct uses concentration gradient to adjust urine volume and concentration.
An example of a antidiuretic hormone drug is...
Vasopressin, same function as ADH
How does a diuretic affect urine flow rate?
a diuretic is a substance that causes increased urine flow rate
What does an antidiuretic do to urine flow rate?
an antidiuretic causes decreased urine flow rate
What effect does ADH have on urine flow rate? wall permeability in collecting duct?
ADH decreases urine flow rate, so it must make walls of duct more permeable
ADH is main control of urine flow rate: high ADH, low flow, water being conserved
-Low ADH, high urine flow, get rid of excess water.
What effects does ADH have on urine concentration?
- High ADH, LOW urine flow rate, HIGH concn. (mostly due to NaCl)
- Low ADH, HIGH urine flow rate, LOW concn. (mostly due to NaCl)
What are the capillaries that run alongside Loop of Henle called? Are these capillaries permeable to water and ions? if so, how permeable?
run alongside loop of H., called vasa recta
- Vasa recta freely permeable to water and ions
When ADH is high & water being reabsorbed from collecting duct, explain ion and water exchange between peritubular capillary blood and tubule as blood moves thru.(hint: exchange different for ascending and descending capillaries that run along ascending and descending Convoluted tubule.)
Capillaries called vasa recta.
- As blood moves down v.r., picks up ions, loses water
- As blood moves up v.r., loses ions, picks up water
- If water is being reabsorbed, blood in v.r. will leave with more water than it came in with
About __% of filtered urea is passively reabsorbed in PCT
About 50% of filtered urea is passively reabsorbed in PCT
How does countercurrent multiplication effect urea concentration in Medulla?
causes passive buildup of urea in medulla
When ADH present, but not aldosterone ____ is concentrated due to water loss, although not as high as ____ because collecting duct slightly permeable to ____. (Fill in blanks with NaCl or Urea, use one twice)
When ADH present, UREA is concentrated due to water loss, although not as high as NaCl because collecting duct slightly permeable to UREA
How is urea concentration slightly elevated even with high urine flow? (No ADH)
When ADH absent, slight perm. of urea in coll. duct allows some urea to diffuse into duct, so even with high urine flow, urea concn. slightly elevated
physiological term for urination, or emptying the bladder...
Micturition
________ in ureters forces urine through one-way valves into bladder.
Peristalsis
Is control of Micturition spinal reflex or voluntary?
Partially both
Bladder volume maximum is...
750-800mL
As bladder fills, ______(1) in wall triggered.
- _______(1) send ________(2) to spinal cord
- Spinal cord sends ______(2) to _______(3) in bladder wall
- Pulse of contraction in bladder wall further stimulates ______(1)
- Causes feeling of fullness, urge to urinate
- If bladder not very full, dies out after minute or 2
- If bladder more full, causes ring of muscle, __(name of muscle)__, to open
As bladder fills, stretch receptors(1) in wall triggered.
- Stretch receptors(1) send action potential(2) to spinal cord
- Spinal cord sends actn.(2) pots. to smooth muscle(3) in bladder wall
- Pulse of contraction in bladder wall further stimulates stretch receptors(1)
- Causes feeling of fullness, urge to urinate
- If bladder not very full, dies out after minute or 2
- If bladder more full, causes ring of muscle, internal urethral sphincter, to open
How do non-infants stop from urinating when they have the urge to urinate?
mainly by using external urethral sphincter (ring of muscle around upper urethra under voluntary control)
When bladder full, can consciously relax ______ and voluntarily trigger micturition reflex to empty bladder
ext. urethral sphincter