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Block 2; Week 4 > Keef 1 > Flashcards

Keef 1 Flashcards

1
Q

85% of the nephrons in the kidney are _____ while 15% are ______.

A

85% cortical

15% medullary

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2
Q

What is the main distinguishing feature of juxtamedullary nephrons?

A

They have long loops of Henle that push into the medulla & even into the papillary region. These are responsible for creating the osmotic gradient in the interstitial space.

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3
Q

What type of tissue does the exchange happen across in nephrons in the kidney?

A

Simple squamous epithelium

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4
Q

T/F the cortical nephrons don’t have a loop of Henle & don’t significantly contribute to the osmotic gradient in the interstitial space.

A

False. They do have a loop of Henle. But it is true that they don’t significantly contribute to the osmotic gradient.

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5
Q

Where does the fluid go after it gets to the distal convoluted tubule of the cortical & juxtamedullary nephrons?

A

They both drain into the common collecting duct. Here stuff happens based off of the osmotic gradient created by the juxtamedullary nephrons.

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6
Q

Where is the nephron permeable to water & where is it not?

A

In areas where filtration dominates: like the glomerulus & PCT & descending limb of the loop of Henle it is very permeable. In areas where absorption dominates: like the ascending limb of the loop of Henle & the DCT…it is very impermeable.

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7
Q

When we talk about permeability…what tissue are we talking about?

A

We are talking about the simple squamous epithelium lining the nephron…it is made of tight jcns in areas that are impermeable.

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8
Q

What types of proteins make up the tight jcns b/w the epithelial cells in the nephron?

A

Claudin
Occludin
*in the paracellular space

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9
Q

What is something that could cause a rupture of the tight jcn b/w the epithelial cells?

A

Ischemia, Disease, Mutation

Bad situation.

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10
Q

What is the relationship b/w portions of the nephron, filtration/absorption, tight jcns, & resistance?

A

As you move from the glomerulus to the PCT to the loop to the DCT to the collecting duct…
Resistance increases.
This means that there are more tight jcns as you move along.
This means that the area is less permeable as you move along.
This means that less filtration happens & more absorption happens as you move along.

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11
Q

What is another name for antidiuretic hormone (ADH)?

A

arginine vasopressing (AVP)

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12
Q

What does ADH do to the nephron?

A

It greatly increases the permeability of the collecting duct (not by messing w/ the tight jcns) but by inserting aquaporins (proteins that create holes).

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13
Q

If ADH is not present…what happens to those aquaporins it inserted into the collecting duct?

A

They are taken out/degraded.

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14
Q

Where is the location of aquaporins that are always there–not dependent on ADH? Where is the location of aquaporins that are only present w/ the presence of ADH?

A

Aquaporins in the proximal convoluted tubule are always there.
Aquaporins in the collection duct are dependent on ADH.

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15
Q

What are the different capillaries that are found w/ the cortical nephron & juxtamedullary nephrons?

A

Both have glomerular capillaries (afferent arteriole leads into this capillary & efferent arteriole leads out)
After this they both have a peritubular capillary surrounding the nephron.
BIG DIFFERENCE:
Only the juxtamedullary nephrons have the vasa recta capillary (it surrounds the big long loop of Henle).

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16
Q

Which of the capillaries in the nephron are low pressure & which are high pressure?

A

High Pressure: the glomerular capillaries

Low Pressure: peritubular capillaries & the vasa recta

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17
Q

Where is the first point of resistance in the nephron?

A

The afferent arteriole. Another point of resistance is the efferent arteriole.

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18
Q

What percentage of the renal blood flow goes to the cortex & what percentage goes to the medulla?

A

90% to the cortex.

10% to the medulla

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19
Q

What makes up the juxtaglomerular apparatus?

A

Glomerulus & the nearby portion of the distal convoluted tubule…this includes the JGA cells & the macula densa. Also, the extraglomerular mesanangial cells.

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20
Q

What is the fcn of the JGA cells & the macula densa?

A

JGA cells secrete renin.

The macula dense sense the level of flow in the DCT & feedback to the JGA cells to secrete Renin.

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21
Q

What is tubuloglomerular feedback?

A

Mechanism that tries to keep a constant GFR.
If the macula densa cells in the DCT sense low NaCl caused by low flow…they release substances that will cause JGA cells to secrete Renin (eventual efferent arteriole constriction) & substances that directly dilate the afferent arteriole. This increases GFR.

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22
Q

What does low NaCl @ the macula densa translate to a GFR that is too low?

A

B/c if GFR is too low b/c arterial pressure is too low or something there will be less flow in general in the nephron…NaCl is absorbed into the interstitial space in the ascending limb of the loop of Henle…of course some of this salt stays in the filtrate…if the macula densa in the DCT senses less NaCl than normal–that indicates lower flow than normal & calls for increased pressure in the glomerulus.

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23
Q

What is the mediator in the mechanism of tubuloglomerular feedback that tries to correct a GFR that is too high?

A

Mediator: adenosine

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24
Q

What are the modulators in the mechanism of the tubuloglomerular feedback that tries to correct a GFR that is too high?

A

NOS 1, COX-2, Ang II

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25
Q

What is different about the filtration/absorption that happens in the capillaries of skeletal muscle vs. kidneys?

A

Skeletal muscle they both happen along the same capillary. You observe a hug pressure drop after the arterioles.
Kidney you have 2 capillaries (High P of the glomerular capillary–only filtration) & (Low P of the peritubular capillary–only absorption).
Kidneys–b/c you have arterioles on each side…you have a relatively constant pressure over the entire capillary.

26
Q

What is the important equation for blood flow in the kidney?

A 
Blood Flow (Q) = delta P/R.
The P refers to the pressure entering & exiting the kidneys.
27
Q

How does renal blood flow change if you contract the afferent arteriole vs. the efferent arteriole?

A

If you contract either arteriole (doesn’t matter which) it will cause a decrease in renal blood flow.

28
Q

How does glomerular pressure change if you contract the afferent arteriole vs. the efferent arteriole?

A

Glomerular pressure will increase if you contract the efferent arteriole. Note: this will increase GFR. It will decrease if you contract the afferent arteriole. This will decrease GFR.

29
Q

What are the 2 things that can cause an increase in glomerular pressure & GFR?

A

Dilation of the afferent arteriole & constriction of the efferent arteriole.

30
Q

T/F An increase in glomerular pressure will always cause an increase in the GFR.

A

True.

31
Q

What has a more powerful effect on increasing GFR: dilation of the afferent arteriole? Or constriction of the efferent arteriole?

A

Dilation of the afferent arteriole. B/c it also increases renal blood flow. It is a more powerful mechanism.

32
Q

Dilation of the afferent arteriole does what to:
Renal Blood Flow
Glomerular Pressure
GFR?

A

Renal Blood Flow–increases
Glomerular Pressure–increases
GFR–really increases

33
Q

Dilation of the efferent arteriole does what to:
Renal Blood Flow
Glomerular Pressure
GFR?

A

Renal Blood Flow–increases
Glomerular Pressure–decreases
GFR–decreases

34
Q

Constriction of the afferent arteriole does what to:
Renal Blood Flow
Glomerular Pressure
GFR?

A

Renal Blood Flow–decreases
Glomerular Pressure–decreases
GFR–decreases a lot

35
Q

Constriction of the efferent arteriole does what to:
Renal Blood Flow
Glomerular Pressure
GFR?

A

Renal Blood Flow–decreases
Glomerular Pressure–increases
GFR-increases

36
Q

What is the equation for filtration fraction?

A

Filtration Fraction = GFR/Renal Plasma Flow

37
Q

What is the approximate filtration fraction for the kidney?

A

~20%. This means that 20% of the blood that flows into the kidney is filtered by the nephron (goes thru the glomerulus into the tubes).

38
Q

What happens to the filtration fraction when you constrict the efferent arteriole? Why?

A

The filtration fraction increases when you constrict the efferent arteriole.
GFR increases & Renal plasma flow decreases.

39
Q

What happens to the filtration fraction when you dilate the efferent arteriole? Why?

A

The filtration fraction decreases when you dilate the efferent arteriole.
GFR decreases & Renal plasma flow increases.

40
Q

T/F the kidney is one of the organs that is capable of auto regulation of blood flow.

A

True. This is important b/c it shields the kidneys from the crazy spastic changes in pressure in the body. : ) This also keeps the GFR relatively constant.

41
Q

What is auto regulation of blood flow–esp as it applies to the kidney?

A

Based on the equation: Blood Flow= change in P/R
It says that if the pressure difference increases the arteriole will constrict so that resistance also increases. This will allow the blood flow to remain constant.

42
Q

What are the 2 mechanisms that allow for auto regulation of renal blood flow?

A
  1. Myogenic Mechanism. The idea that an increased pressure will stretch the arteriolar walls & cause a natural response of constriction. This will decrease blood flow.
  2. Tubuloglomerular feedback–mainly the increase in afferent arteriolar resistance w/ high arterial pressure.
43
Q

T/F The auto regulation of blood flow in the kidney is independent of the sympathetic nervous system.

A

True.

44
Q

T/F The auto regulation of blood flow in the kidney involves predominately the postglomerular efferent arteriole.

A

False.

45
Q

What is the effect of sympathetic nerves on the kidney?

A

Okay…so usu not much of an effect.
However, the kidney is densely innervated by the sympathetic nervous system.
Usu not activated on a daily basis.
In cases of severe hypovolemia could decrease renal blood flow.

46
Q

What are 3 things that regulate renin release?

A

Less stretch on the afferent arteriole–direct renin release.
Less GFR & less flow in ascending limb of the loop of Henle–less salt delivered to the macula densa–renin release.
Baroreceptors sense low Pa–brain–symp nerve fibers–renin release.

47
Q

What is acute renal failure?

A

sudden loss of kidney function
this results in retention of urea & other nitrogenous waste
this results in dysregulation of extracellular volume & electrolytes.

48
Q

Why can Congestive Heart Failure & NSAIDs lead to acute renal failure?

A

CHF causes low perceived blood volume @ the baroreceptors.
Ang II & Symp responses cause both the constriction of the renal arterioles & the release of prostaglandins (which dilate the arterioles). These counteract & allow for a normal renal blood flow.
NSAIDs block the prostaglandins & block the dilation. This causes severely reduced renal blood flow & acute renal failure.

49
Q

What is secondary hyperaldosteronism? What is an example of this?

A

It is excessive levels of aldosterone. It isn’t b/c of a problem w/ the adrenal cortex, however. It is b/c of a secondary issue–> like RAS…release of Renin–>Ang II–>more aldosterone.

50
Q

How can taking ACE inhibitors when you have RAS cause acute renal failure?

A

The stenosis of the renal artery causes reduced pressure in the afferent arteriole. This prompts renin release. This forms Ang I. Ang I–> Ang II w/ ACE. The Aldosterone levels that go along w/ Ang II levels will cause HTN & if a patient takes ACE inhibitors it will block the Ang II & its constriction of the efferent arteriole. This is all that allows the RAS patient to keep his GFR up. Now, it decreases dramatically & he is in acute renal failure.

51
Q

What is the relationship b/w renal oxygen consumption & GFR?

A

As GFR increases, more oxygen is consumed.

52
Q

What is the relationship b/w renal oxygen consumption & sodium reabsorption?

A

As sodium reabsorption increases, oxygen consumption increases. This should make sense b/c sodium absorption is a process that requires a lot of energy–b/c of the Na+/K+ ATPase.

53
Q

Which of the following has a greater GFR?
A. Arterial O2 content: 0.2; Renal Venous O2 content: 0.18; Renal Blood Flow: 600
B. Arterial O2 content: 0.2; Renal Venous O2 content: 0.16; Renal Blood Flow: 600

A

B has the greater GFR b/c it has the greater oxygen consumption.

54
Q

Which of the following has the greater filtration fraction?
A. Arterial O2 content: 0.2; Renal Venous O2 content: 0.18; Renal Blood Flow: 600
B. Arterial O2 content: 0.2; Renal Venous O2 content: 0.16; Renal Blood Flow: 600

A

B. B/c
Filtration Fraction = GFR/ Renal Plasma Flow
They both have the same renal plasma flow. B has a greater GFR.
B wins w/ filtration fraction!! Yay!

55
Q

Will this result in decreased oxygen consumption?

Blockage of tubular sodium/potassium pump.

A

Yes.

56
Q

Will this result in decreased oxygen consumption?

Contraction of the efferent arteriole.

A

No. B/c this increases GFR.

57
Q

Will this result in decreased oxygen consumption?

Severe hemorrhage.

A

Yes

58
Q

Will this result in decreased oxygen consumption?

Contraction of the afferent arteriole.

A

Yes. b/c decreases GFR.

59
Q

Will this result in decreased oxygen consumption?

Tubular necrosis.

A

Yes.

60
Q

What does ouabain do?

A

It blocks the sodium potassium pump.

Block 2; Week 4 (6 decks)

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