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Med Physiology Certificate > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

The kidney makes: ______________________, _______________________, such as _____________________ and ____________________ in the active form

A

Renin
Hormones
Erythropoietin
Vit D

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2
Q

Once urine is formed and exiting the medulla, it enters the ___________ calyx then the ___________ calyx and further into the renal ______________ and finally to the ureter

A

minor
major
pelvis

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3
Q

As the interlobar artery flows up the renal pyramid, it then runs parallel across the medulla and cortex where the artery is now termed , _________________ artery. These artery then run perpendicular up into the medulla and are now termed: _________________ artery. The _____________ arteriole branch off of the interlobar artery

A

Arcuate artery
Interlobar artery
afferent

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4
Q

The ______________ comprise 90% of the total glomeruli of the kidney and are located in the outer 2/3 of the cortex. The remaining 10% are termed: _____________

A

Cortical glomeruli
Juxtamedullary glomeruli

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5
Q

The peritubular capillaries are found:
They surround the _________________ and ___________________ ________________

A

Entirely in the cortex
Proximal and distal tubules

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6
Q

What are some differences of the juxtamedullary glomeruli?

A

1.) Deep within the cortex, proximal to the medulla
2.) The efferent arteriole from the glomeruli form the vasa recta that are vital to concentrating urine
3.) The vasa recta stretch deep into the medulla

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7
Q

The glomerular capillary is surrounded by:

A

Bowman’s capsule

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8
Q

Bowman’s capsule is formed by epithelial cells which then stretches on to form the:

A

Proximal tubule

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9
Q

The glomerulus has capillary ___________. When filtration occurs, the ______________ and ________________ ________________ of the plasma are forced across the capillary wall known as filtration.

A

loops
water
small solutes

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10
Q

T/F: The glomerulus itself cannot contract since it is comprised of capillary loops

A

False, in the central core of the glomerulus there is mesangial cell that can contract

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11
Q

List some functions of the mesangial cell

A

Contractile
Synthesizes products
Role in phagocytosis and immunity

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12
Q

In the glomerular capillary loop, there is a layer of endothelial cells. These cells like on a basement membrane that is proximal to Bowman’s capsule. Outside of the basement membrane exists the huge cell type:

A

Podocyte

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13
Q

What do podocytes do?

A

Within Bowman’s capsule inside the glomerular filtrate that give rise to “footlike projections” that surround the basement membrane of glomerular capillary.

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14
Q

What does fenestrated mean?

A

With perforations

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15
Q

What is the basement membrane within the glomerulus made of?

A

Gel layer that is supported by a matrix

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15
Q

T/F: Only the juxtamedullary glomeruli have a loop of Henle extending into the medulla

A

False, both have a loop of Henle extending into the medulla. The JMG extends much deeper into the medulla

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16
Q

What is the macula densa?

A

The portion of the thick ascending loop of Henle that is making contact with the afferent arteriole of the glomerulus

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17
Q

Where do you find the peritubular capillaries? Where do you find the vasa recta capillary network?

A

1.) surrounding the tubules of the superficial glomeruli
2.) Vasa recta ascending and descending run parallel to the loop of Henle of the juxtamedullary glomeruli

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18
Q

What is the Juxtaglomerular apparatus comprised of?

A

Macula densa + extraglomerular mesangium + terminal portion of the afferent arteriole

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19
Q

The thick ascending loop of Henle contacts with the afferent arteriole. What specialized cell type are going to communicate with the terminal portion of the afferent arteriole?

A

Cells termed macula densa communicate with extraglomerular mesangial cells

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20
Q

What two things are being communicated between the macula densa and mesangial cells at the Juxtaglomerular apparatus?

A

1.) Communicate to influence vascular tone if the afferent arteriole
2.) Communicate to influence granular cells that are at the top of the glomerulus underneath the afferent arteriole

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21
Q

Where are granular cells? What do they do? What is their structure type?

A

1.) Cells near the top portion of the glomerulus
2.) They synthesize renin and release
3.) specialized smooth muscle

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22
Q

What is the term for the side of epithelial cells that faces the tubule lumen?

A

Luminal or apical surface

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23
Q

What connects the epithelial cells lining the nephron tubules?

A

Tight junctions

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24
Q

What is the term for the epithelial cells that are facing the interstitial fluid of the nephron?

A

Peritubular or basolateral

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25
Q

Where are the Na+/K+ ATPase transporters found in the epithelial cells of the tubule

A

On the peritubular/basolateral side only so that sodium can only be reabsorbed back into the body

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26
Q

Why is the proximal tubule have a brush border?

A

Active site of reabsorption

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27
Q

Name the two types of cells found in the cortical collecting duct

A

1.) Principal cell
2.) Intercalated cell

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28
Q

T/F: Like most organ systems, the parasympathetic and sympathetic play a significant innervation role in the renal system

A

False, controlled by sympathetic. NO significant parasympathetic innervation

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29
Q

Glomerular filtration rate is normally very high. The normal is approx:

A

80-200 ml per minute

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30
Q

What are the 6 requirements of a substance to be used to measure GFR

A

1.) Freely filtered at the glomerulus so it will reach the tubule
2.) Not reabsorbed in the tubule
3.) Not secreted in the tubule
4.) Not metabolized
5.) Not toxic
6.) Not effect on the kidney

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31
Q

When determining if a substance is appropriate to use for GFR calculation, the amount filtered must be equal to the:

A

Amount excreted in the urine

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32
Q

(If freely filtered) Rate of filtration of substance X =

A

Plasma concentration x (Px) * GFR

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33
Q

Rate of excretion of substance X =

A

Urine concentration of X * urine flow rate (v)

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34
Q

Why is inulin used to measure GFR?

A

Because it cannot cross the cell wall of the tubule

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35
Q

If you have concentration of urine and plasma, what is the equation to calculate GFR?

A

GFR = ( [Ux]/[Px] ) * v
where Ux is urine concentration of substance X
Px is plasma concentration of substance X
v is urine flow rate

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36
Q

What is an endogenous substance that can be used to measure GFR? What is the drawback to this substtance?

A

Creatinine is freely filtered and not reabsorbed made in skeletal muscle
Drawback: there is some tubule secretion downstream from glomerulus so there is a little bit more creatinine cleared than is filtered at the glomerulus

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37
Q

What endogenous substance is typically used to measure GFR?

A

Creatinine

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38
Q

Creatine production matches creatinine excretion. Therefore, if GFR halves, what happens to plasma concentration Creatinine?

A

Its plasma concentration doubles

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39
Q

The higher the plasma creatinine, the:

A

lower the GFR

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40
Q

Why must creatinine measurement be adjusted when calculating GFR?

A

It can be affected in the setting of pregnancy, muscle wasting disease, and aging

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41
Q

What are three additional factors to consider when calculating eGFR from creatinine clearance?

A

Age, body weight in Kg, and sex

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42
Q

What is the clearance equation?

A

Cx = ( [Ux] / [Px] ) * V
C clearance substance X
U concentration of substance X
Plasma concentration of substance X
urine flow

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43
Q

Define clearance of a substance

A

A volume of plasma from which all of the substance is removed per unit time

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44
Q

T/F: Urinary clearance is the same as renal clearance

A

True

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45
Q

What is the equation for final urinary excretion of a substance?

A

[Ux] V = filtered x - reabsorbed x + secreted x

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46
Q

What is fractional clearance?

A

Method used to evaluate how the kidney handles a particular substance compared to how the substance is filtered
Compare the clearance to inulin, such that if clearance is the same of substance X compared to inulin, then it is considered freely filtered

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47
Q

If clearance substance X is < clearance inulin, what does this tell you?

A

There is reabsorption

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48
Q

Is clearance of substance X greater than or less than inulin clearance when there is secretion of substance X

A

Clearance substance X is greater than clearance inulin = substance X secretion

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49
Q

_______________ and _________________ are two examples of substances that are entirely (or almost entirely) reabsorbed and filtered by the kidney

A

Glucose (entirely reabsorbed normally)
Phosphate (mostly reabsorbed)

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50
Q

What is the normal plasma glucose?

A

100 mg/dL

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51
Q

What happens when the filtered load of the glomerulus is overloaded?

A

The substance is excreted through the urine

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52
Q

What is the expected fractional clearance of glucose? How would it compare to the fractional clearance of inluin?

A

Fractional clearance glucose is 0.0
Is lower to inulin because all of the glucose is reabsorbed rather than entirely excreted

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53
Q

What is the fractional clearance of phosphate?

A

0.2

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54
Q

Where is phosphate absorbed? What is its absorption coupled to?

A

Absorbed at the proximal tubule and coupled to sodium absorption

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55
Q

Why is fractional clearance of phosphate greater than factional clearance of glucose?

A

Because the reabsorptive capacity of phosphate is lower in the proximal tubule

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56
Q

What does phosphate’s fractional clearance of 0.2 actually mean?

A

20% of the filtered phosphate is excreted while the remaining 80% is absorbed

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57
Q

What is the fractional clearance of water?

A

0.01

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58
Q

What is the approx. amount of water being filtered at the glomerulus per minute?

A

~120 mL/min

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59
Q

Water reabsorption is ___________________ along the nephron

A

Passively

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60
Q

How does the changing concentration of inulin in the kidney relate to water reabsorption?

A

The plasma concentration of inulin is going to be less than what is excreted. This is because as inulin travels down the tubule, water is being reabsorbed which makes the concentration of inulin greater

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61
Q

Urine to plasma concentration (U/Pin) ratio of:
1 means:

A

U/Pin ratio of 1 means there is equal plasma concentration of inulin compared to urine [inulin]. If there was water absorption then the urine concentration would be high. Thus NO water reabsorption

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62
Q

Urine to plasma concentration (U/Pin) ratio of:
2 means:
Why?

A

U/P in ratio of 2 means the urine [inulin] is greater than plasma [inulin], thus some water is reabsorbed since the urine concentration is higher as the inulin traveled down the tubule. More specifically, 50% of water is reabsorbed

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63
Q

Urine to plasma concentration (U/Pin) ratio of:
100 means:
Why?

A

U/ Pin ratio of 100 means almost all of the water is reabsorbed since the urine [inulin] is much much greater than the plasma [inulin]
In normal humans, 99% of water is reabsorbed and 1% is excreted

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64
Q

Define free water of the body

A

Solute free, pure (distilled) water

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65
Q

What is free water clearance?

A

Comparing the volume of free water leaving the body compared to solute

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66
Q

What is the question to calculate free water clearance?

A

Clearance H20 = V - C osm
V is urine flow rate (Total amount of water leaving body)
C osm is osmolar clearance

C osm = U [osmolar] / P [osmolar] * V

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67
Q

What is the difference between tonicity and osmolarity?

A

Osmolarity can describe the state of solution vs cell and vice versa
Tonicity describes the state of the solution ONLY

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68
Q

What does it mean physiologically if there is positive free water clearance?

A

This means the urine flow rate, V, is greater than osmolar clearance. Such that the urine being excreted is hypo-osmotic and dilute

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69
Q

What does it mean if there is negative free water clearance?

A

Means the osmolar clearance is greater than urine flow rate, V. Thus the excreted urine is hyper-osmotic and more concentrated compared to plasma

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70
Q

What is the fractional clearance of urea?

A

~ 0.2 - 0.6

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71
Q

Urea is a _______________ product of ___________________ metabolism. Made in the __________________ and released into circulation for excretion by the kidney.

A

Waste
protein
liver

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72
Q

Urea is small and thus: _____________ _____________ into the tubule. And cross the tubule wall via:
Thus the, the MORE water absorption =

A

Freely filtered
Passive movement across the tubule wall down its concentration gradient
the more water absorption means more urea reabsorption since the leaving of H20 concentrates the urine creating a concentration gradient

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73
Q

Normally urea excretion and fractional clearance of urea are both low due to:
This means the blood urea nitrogen is:

A

Large water reabsorption which urea follows
High

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74
Q

What does comparing the plasma creatinine and BUN allow us to do clinically?

A

Determine dehydration VS kidney disease
If both go up this means GFR is falled = CKD
BUN up only = dehydration

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75
Q

The comparison of plasma creatinine and BUN can indicate difference between dehydration and CKD, why?

A

Creatinine is an endogenous substance that can be used to calculate GFR
BUN indicates the amount of water being excreted/reabsorbed because urea excretion is opposite BUN. Urea excretion and fractional clearance correlates to water absorption/excretion.

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76
Q

If BUN and creatinine levels go up what does this indicate and why?

A

CKD
Because creatinine filtration is supposed to match excretion under normal GFR. If creatinine levels go up, then the GFR went down

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77
Q

If BUN only goes up, what does this indicate and why?

A

Dehydration
This is because urea effectively follows water absorption/excretion
If urea is up, then water absorption is up due to the body needing to hydrate itself with water available

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78
Q

Urea is _________________ in the PCT and inner medullary collecting duct. Urea can be ________________ into the thin ascending loop of Henle.

A

Reabsorbed
Secreted

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79
Q

Clearance of urea is always <, >, or = to the clearance of inulin. Why?

A

C urea < C inulin because all plasma inulin should be excreted while plasma urea will be reabsorbed following flow of water

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80
Q

The para-aminohippuric acid fractional clearance is:
What does this mean

A

~ 5.0
Means the PAAH is secreted into the tubule

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81
Q

Why is plasma clearance of PAAH (para-aminohippuric acid) equal to the renal plasma flow rate?

A

Because, all PAAH from the plasma is secreted into the tubule for secretion = the volume is corresponding to the amount of plasma flowing through the kidney

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82
Q

Why is creatinine fractional clearance greater than clearance inulin?

A

Because while they are both freely filtered and entirely excreted, there is some tubular secretion of creatinine into the urine which raises the fractional clearance

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83
Q

Inulin and _____________ are perfect markers for GFR calculation but are not clinically used because they are not endogenous

A

Iothalamate

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84
Q

Describe the concentration of sodium and potassium in the intracellular and extracellular compartments
What maintains this composition?

A

INTRAcellular: High K+, Low Na+

EXTRAcellular: High Na+, Low K+

Na/K ATPase

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85
Q

Describe the concentration of protein inside the cell, in the interstitium, and within the plasma

A

INTRAcellular: 30 g/dl

Interstitium: 1 g/dl

Plasma: 7 g/dl

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86
Q

How much Na is reabsorbed?

A

The majority of it, 99%

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87
Q

Where are the ONLY two places that Na+ transport does NOT occur?

A

Descending loop of Henle and Thin ascending loop of Henle

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88
Q

Where does bulk reabsorption of sodium occur?

A

In the proximal tubule

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89
Q

What stimulates sodium reabsorption in the PCT?
What inhibits sodium reabsorption in the PCT (minor role)?

A

Stimulate: alpha-adrenergic nerves & ANG II
Inhibited: Atrial naturetic peptide and nitric oxide

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90
Q

How many “Stages” of sodium transport exist in the proximal tubule?

A

2

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91
Q

Describe sodium transport at the Early proximal tubule

A

The NHE3 major transporter
1.) The cell generates a H+ inside the cell and exchanges this ion for a Na+ from the tubule lumen
2.) Electrically neutral exchange
3.) Na+ is removed and put back into the body (interstitum) via Na+//K+ ATPase

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92
Q

What is the primary absorptive mechanism of sodium at the early PCT?

A

Na+ - H+ Exchange aka NHE3

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93
Q

Where does the NHE3 transporter exist? What type of transport occurs here?

A

At the early PCT
Uses secondary active transport using the energy generated from the Na+/K+ transporter on the apical side of the tubule

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94
Q

In the early PCT, what is significant about the H+ ion secretion?

A

The H+ drives bicarbonate reabsorption

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95
Q

T/F: The early PCT only reabsorbs sodium via NHE3 transporters

A

False, sodium transport also coupled to glucose, amino acid, phosphate, and lactate absorption

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96
Q

Describe the movement of Chloride in the early PCT

A

Leaks through channels into the interstitium

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97
Q

Describe the movement of H20 and sodium at the early PCT

A

Iso-osmotic. Water follows sodium transport

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98
Q

Why does solute concentration fall moving down the PCT?

A

Because it’s all been absorbed early in the PCT

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99
Q

Describe solute movement at the late PCT

A

1.) H ion + waste anions form H anion and are reabsorbed
2.) The anion breaks apart in the cell to release a H+ and anion
3.) Outward moving H+ couples with Na+ exchange while anion couples with Cl- exchange, thus Na+ and Cl- going into the cell
4.) The concentrated Cl- tubular fluid drives Cl-/Na+ down its concentration via paracellular diffusion into the peritubular capillary

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100
Q

Describe sodium movement at the Loop of Henle

A

Nothing in descending or ascending thin loop of Henle
Thick ascending loop of Henle, 25% Na sodium reabsorbed

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101
Q

What stimulates sodium reabsorption at the loop of Henle?
What inhibits sodium reabsorption?

A

Stimulate: alpha adrenergic nerve, Angiotensin II
Inhibit: prostaglandin

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102
Q

List the two transporters responsible for sodium exchange in the thick ascending loop of Henle

A

1.) NHE3, minor contributor
2.) Sodium potassium 2 Cl- Co-transporter (major transporter)

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103
Q

What is the abbreviation for the sodium potassium, 2 chloride co-transporter present in the TALH

A

NKCC2 transporter

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104
Q

What drives the NKCC2 co-transporter in the TALH?

A

ROMK channels
Potassium channels that allow K+ to flow down its concentration gradient into the tubular lumen

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105
Q

How does Na, K+, Cl- get into the interstitium?

A

Na+/K+ ATPase
K+/Cl- co-transporter
Both on the apical side

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106
Q

Other than supplying K+ in the TALH, what else is significant about the ROMK presence on the luminal cell side?

A

It creates a small + charge within the tubule lumen

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107
Q

What is special about the NKCC2 pump?

A

It is involved in signal transduction at the macula densa

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108
Q

T/F: The thick ascending limb is the site of sodium and water reabsorption

A

False, sodium reabsorption only. Always Impermeable to water!

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109
Q

How much sodium is reabsorbed by the distal tubule?
What stimulates this absorption?
What inhibits it?

A

~10%
Stimulated by: Aldosterone and Angiotensin II
Inhibited by: Atrial naturetic peptide and nitric oxide

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110
Q

What is the major controller of how much sodium is reabsorbed at the distal tubule and collecting duct?

A

Aldosterone

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111
Q

What transports sodium from the lumen in the distal tubule?

A

The NCC co transporter

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112
Q

What is special about the NCC transporter? Where is it located?

A

Thiazide sensitive
Distal tubule for sodium and Cl reabsorption

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113
Q

How does Aldosterone increase sodium reabsorption at the distal tubule?

A

Increases the number of NNC transporters in the luminal membrane
Also increases ATP to increase Na/K ATPase activity for more sodium to go back into the interstitium
Can even increase quantity of Na/K ATPase pumps

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114
Q

List the two different cell types of the collecting duct

A

1.) Principle
2.) Intercalated cell

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115
Q

Describe the movement of sodium and potassium in and out of the lumen in the principle cells of the collecting duct

A

1.) Sodium flows down its concentration gradient through epithelial sodium channels
2.) Potassium leaks out of the principle cell down its electrical concentration gradient to balance the negative charge that was established by reabsorption of Na+

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116
Q

What is the name of the epithelial sodium channels found in the collecting duct?

A

ENaC channel

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117
Q

T/F: Amiloride affects the number of ENaC channels in the principle cells of the collecting duct

A

False, Aldosterone influences the number of ENaC channels and causes channels to shuttle to the luminal membrane

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118
Q

Aside from reabsorbing sodium as needed for the body, what is significant about ENaC channels and the absorption of sodium from the collecting duct?

A

The + charged sodium being absorbed into the cell on a large scale creates a negative lumen charge that drives the flow of K+ out of the cell

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119
Q

T/F: Similar to its influence on sodium reabsorption in the principle cells of the collecting duct, Aldosterone also influences the movement of water in the collecting duct

A

False, water reabsorption is influenced by ADH

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120
Q

What diuretic inhibits the NKCC2 transporter? Thus, where is this diuretic acting?

A

Furosemide (Lasix)
Acting Thick ascending loop of Henle

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121
Q

What diuretics inhibit the NCC transporter? Thus, where is this diuretic acting?

A

Thiazides and Metolazone
Acting Distal tubule

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122
Q

What diuretics inhibit the ENaC transporter? Thus, where is this diuretic acting?

A

Amiloride and Triamterene
Collecting duct

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123
Q

What does Spironolactone inhibit? What further implications does this have?

A

Inhibits the actions of Aldosterone by inhibiting the actions of the mineralocorticoid receptors
Thus blocks reabsorption in the Distal tubule and Collecting duct

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124
Q

Describe how diuretics that act ahead of the collecting duct can cause hypokalemia and potassium wasting

A

If there is blocked sodium reabsorption ahead of the collecting duct, once filtrate reaches the collecting duct ENaC will attempt to compensate and reabsorb more Na+ here which will make the tubule lumen more negative and thus driving K+ out of the cell for excretion

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125
Q

Why is Amiloride considered a potassium sparing diuretic?

A

Because it blocks sodium reabsorption at the collecting duct, thus preventing the electrical concentration gradient formation to drive potassium out of the cell and into the lumen

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126
Q

Why does the sodium concentration in the ECF remain fairly constant even if sodium amount changes?

A

A change in sodium content reflects subsequent change in fluid volume to maintain concentration

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127
Q

In negative Na balance: Output > intake. Na ____________ occurs and ECF volume ____________. Which can lead to circulatory collapse and organ failure

A

Depletion
decreases/falls

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128
Q

In Positive Na balance: Output < intake, Na _____________ occurs and ECF volume __________________. Which can lead to edema

A

accumulates
Increases

129
Q

What is the basic premise of Glomerular tubular balance

A

Limits how much sodium is excreted

130
Q

Describe how glomerular tubular balance works.

A

The increased sodium filtration would theoretically lead to increased urine excretion
With GTB, the PCT increases the amount of Na reabsorbed so that the PCT is always absorbing a CONSTANT FRACTION of the filtered Na
Since this is the largest site of Na reabsorption this protects excess excretion

131
Q

What determines Sodium Excretion aka UNaV

A

Filtered Na - Reabsorbed Na

132
Q

What are two mechanisms proposed to account for glomerulotubular balance?

A

1.) Luminal control
2.) Starling pressures

133
Q

Describe luminal control and its relation to glomerulotubular balance

A

Flow dependent response/sensor at the PCT where increased Na delivery is sensed and automatically increases reabsorption of Na proportion

134
Q

What are two mechanisms for sodium retaining? What activates these?

A

Act as vasoconstrictor & Change tubular Na reabsorption mechanisms
Renin angiotensin/Aldosterone system
Sympathetic nervous system
Activated by Sodium depletion

135
Q

What are Naturetic systems? What activates these?

A

Activated by excess sodium, volume expansion, increased BP
Atrial natriuretic peptide and nitric oxide acting as vasodilators and increase GFR

136
Q

Describe the activation of RAAS

A

1.) Fallen sodium reabsorption = fallen total body volume
2.) Sensed by granular cells and they release renin into the blood
3.) The renin is an enzyme that acts on angiotensin to convert it to ANG I
4.) Then ANG I is converted to ANG II by converting enzyme

137
Q

Describe what happens to sodium excretion when GFR is lowered

A

Lowered GFR = lowered sodium excretion

138
Q

Describe 3 mechanisms of action of ANG II

A

1.) Ang II acts on renal circulation to lower GFR
2.) acts on PCT and TALH to increase Na reabsorption
3.) acts on adrenal cortex to stimulate aldosterone

139
Q

_______________ is a steroid hormone, (mineralocorticoid) made in the adrenal cortex

A

Aldosterone

140
Q

T/F: Aldosterone not only influences sodium excretion but also, potassium and H+ excretion

A

False, it does increase K+ and H+ excretion but also sodium RETENTION

141
Q

Explain how aldosterone physically acts on the principle cells of the collecting duct

A

1.) Aldosterone transports from the blood to the basolateral side of the principle cell
2.) Aldosterone interacts with mineralocorticoid receptor
3.) This aldosterone/mineralocorticoid receptors interacts with the nucleus
4.) Initiates transcription and protein synthesis
These proteins act in an immediate response
5a.) More open ENaC on luminal side
5b.) Proteins activate mitochondrial enzymes to make more ATP to increase Na/K ATPase
5c.) over days, larger quantity of Na/K+ ATPase pumps

142
Q

What stimulates aldosterone release from the adrenal gland?

A

Increased plasma potassium increases aldosterone release

143
Q

T/F: ANG II can DIRECTLY increase aldosterone release

A

True

144
Q

Why is fallen plasma sodium level not considered a major contributor to aldosterone release?

A

Because the kidneys work to maintain constant plasma sodium levels, thus ideally this level will not waiver and NOT contribute aldosterone release

145
Q

What controls ANG II release?

A

Renin release

146
Q

What is stimulating the granular cells and subsequent renin release when baroceptors sense fallen renal perfusion at the afferent arteriole?

A

Beta adrenergic action stimulates granular cells

147
Q

How does lowered afferent arteriole pressure influencing action at the macula densa?

A

If there is lowered pressure, there is lowered renal plasma flow and thus lowered filtration at the glomerulus. Thus less sodium is sent into the filtrate. The macula densa in the DCT senses this reduced sodium delivery

148
Q

Once the macula densa senses a lowered sodium delivery at the DCT, this activates the Juxtoglomerular apparatus. Describe this mechanism of action

A

1.) The macula densa sends signals to the extraglomerular mesangial cells
2.) These cells signal to the granular cells to release renin into circulation

149
Q

Describe the negative feedback mechanism of renin release

A

As plasma ANG II levels increase, there is feedback DIRECTLY on the granular cells to inhibit further renin release

150
Q

What might hypoaldosteronism cause?

A

Disorders such as Addison’s disease
Sodium wasting and low ECF

151
Q

What might hyperaldosteronism cause?

A

Sodium retention (on a short term bases) and volume expansion

152
Q

What is mineralocorticoid escape?

A

It is induced during long term hyperaldosteronism. This will allow the tubules to escape/disregard the normal effects of aldosterone to prevent sodium reabsorption

153
Q

What protects people with hyperaldosteronism from edema?

A

Mineralocorticoid escape

154
Q

T/F: Due to the induction of mineralocorticoid escape a few days after onset of hyperaldosteronism, Na reabsorption, K+ & H+ excretion are all physiologically ignored

A

False, only applies to d/c Na+ reabsorption

155
Q

____-adrenergic fibers supply the renal blood vessels and lead to vasoconstriction.
These fibers also supply the PCT and TALH and lead to increased sodium reabsorption

A

Alpha

156
Q

What two types of fibers innervate the renal system under the sympathetic nervous system?

A

Alpha and Beta Adrenergic fibers

157
Q

The beta adrenergic fibers influence renin release through stimulation of granular cells. How do alpha adrenergic fibers influence renin release?

A

The alpha adrenergic fibers decrease renal plasma flow and GFR
This decreases the NaCl delivery to the macula densa
This is sensed at the juxtoglomerular apparatus and stimulates granular cells and renin release

158
Q

How does ANP (atrial natriuretic peptide) induce naturesis?

A

1.) increases GFR
2.) Acts directly on the collecting duct to inhibit sodium reabsorption
3.) Acts on adrenal gland to inhibit aldosterone release
Filter more and reabsorb less = Na excretion

159
Q

How does Nitric Oxide (NO) induce naturesis

A

1.) Increasing GFR
2.) Acts on the collecting duct to inhibit renal sodium reabsorption
3.) Vasodilator

160
Q

What induces Nitric oxide release?

A

High salt intake since NO is made in the blood vessel endothelium, volume expansion due to high salt intake stimulates release NO

161
Q

What induces release of ANP (atrial natriuretic peptide hormone)

A

hormone made in the cardiac atria is released in response to ECF volume expansion based on the increase in R atrial pressure/atrial stretch

162
Q

How do prostaglandins induce natruesis?

A

Not sure

163
Q

Describe pressure Natriuresis
When is it induced?

A

Occurs within minutes corresponding to abrupt rise in arterial blood pressure
Increased BP inhibits Na-H exchange and Na+/K+ ATPase activity both to decrease sodium reabsorption and water reabsorption

164
Q

List 3 major functions of calcium

A

1.) makes up bones and teeth
2.) nerve and muscle function
3.) intracellular signaling molecule

165
Q

List 3 major functions of phosphate (PO4)

A

1.) Makes up bones and teeth
2.) Buffer
3.) makes up substances in the body
4.) phosphorylation involved in activation and inactivation of enzymes

166
Q

What drives Calcium resorption from the body back into the bone?

A

PTH
Calcitriol

167
Q

What directs the absorption of calcium into the body from the intestine?

A

Calcitriol

168
Q

What directs calcium absorption into the bone?

A

Calcitonin

169
Q

What influences calcium excretion from the kidney?

A

PTH
Calcitonin
Calcitriol

170
Q

Where is most of the calcium in the body?

A

99% is in the bone

171
Q

Of the 1% of total body calcium that is filterable through the kidney, what is the limitation of filtration through the glomerulus?

A

40% of the calcium is protein bound and thus too large to filter through the glomerulus

172
Q

Of the calcium that is filtered, about 2/3 of the calcium is reabsorbed where? Is it active or passive reabosrption?

A

Proximal tubule
Coincides with the reabsorption of Na in the proximal tubule, passive reabsorption

173
Q

In the ______ about 20-25% of ionized calcium is reabsorbed. Is this active or passive reabsorption

A

Thick ascending loop of Henle
Passive reabsorption driven by the + lumen electrical potential made by the K+ recycling

174
Q

Describe the reabsorption of Calcium int he Distal tubule

A

Active transport
Regulation of luminal Ca channels

175
Q

PTH predominantly drives Calcium reabsorption, where does it act?

A

TALH and distal tubule

176
Q

Calciferol increases Ca reabsorption in the:
Calcitonin increases Ca reabsorption in the:
Both are more minor contributors

A

DCT
TALH and DCT

177
Q

How does high plasma calcium inhibit Ca reabsorption in the TALH

A

By activating the Ca sensing receptor in the TALH
This inhibits the NKCC2 channel which decreases the + charge generated here by the K+ recycling
Thus less Ca is reabsorbed

178
Q

_________________ has the same effect as high plasma calcium because this drug also block NKCC2 in the TALH

A

Furosemide

179
Q

Persons at risk of Calcium stones are placed on thiazide diuretics, why?

A

Thiazide diuretics increase Calcium excretion by inhibiting NCC channels in the distal tubule. The mechanism is up for discussion, but since Na reabsorption is correlating to Ca reabsorption the Ca reabsorption is decreased

180
Q

Where is the majority of phosphate (PO4) found?

A

85% in the bone

181
Q

About how much of the total body phosphate is found in the extracellular space and thus filtered through the glomerulus?

A

Less than 1%

182
Q

_________________ Drives phosphate reabsorption from the intestine

A

Calcitriol

183
Q

What drives phosphate into the bone and soft tissue?

A

Calciton

184
Q

What pulls phosphate out of the bone and soft tissue into the body and the kidneys?

A

PTH
Calcitriol

185
Q

What influences excretion of phosphate from the kidneys?

A

Calcitonin and PTH

186
Q

What inhibits phosphate excretion in the kidneys?

A

Calcitriol

187
Q

Describe the reabsorption of phosphate at the PCT

A

Co transports with sodium via active processes meaning it is saturable

188
Q

T/F: Phosphate is not normally excreted in the urine since only 1% of the total body phosphate is filtered in the kidneys

A

False

189
Q

What does PTH do in the PCT in regard to phosphate reabsorption

A

Since reabsorption is an active process here and can be saturated PTH works to lower the transport maximum and thus makes saturation occur sooner
LOWERS phosphate reabsorption

190
Q

_____ is a “nonreabsorbable anion” in the collecting duct and contributes to lumen negativity in the collecting duct

A

PO4

191
Q

Lowered GFR = _____ Plasma phosphate

A

Increased plasma phosphate

192
Q

What is concerning about increased plasma phosphate levels?

A

It can form complexes with calcium and be problematic in other body systems

193
Q

Increased plasma phosphate levels will induce:

A

Higher levels of parathyroid hormone and secondary hyperparathyroidism

194
Q

In terms of hemorrhage, once blood loss exceeds 10% of total volume. The _______ system is activated to increase water retention and at high levels as as a vasoconstrictor

A

ADH

195
Q

Hemorrhage greater than 25% total blood volume starts to see reduced organ involvement and ___________ ___________ _________. In this scenario, the ______________ systems are exceeded capacity. And can lead to Hemorrhagic shock

A

Acute renal failure
Vasoconstrictor

196
Q

What is the long term solution to 25% reduction of blood volume in hemorrhage?

A

Only answer is replenishing blood volume. SNS, &RAAS etc are only sustainable for a limited time

197
Q

_________ _______ is caused by bacterial infection in blood. Massive vasodilation and falls in BP which send volume depletion signals. This causes renal sodium retention and increases in ECFV. The bacteria endotoxin also:

A

Septic shock
Causes capillary leak where fluid and protein leaves the circulation and enter the interstitium causing severe edema

198
Q

List two conditions that can cause underfill of vascular volume but overfill of extracellular fluid volume. Why don’t inhibitory signals help reduce this condition?

A

1.) Liver cirrhosis
2.) Nephrotic syndrome and there is loss of protein that plasma protein falls. This causes fluid to accumulate in interstitium
Kidney becomes unresponsive to NO signaling that would normally reduce sodium absorption

199
Q

Why/how does glucose cause an osmotic effect?

A

There is an excessive amount of glucose that is being allowed into the tubules. These tubules will attempt to reabsorb the glucose. The remaining glucose will accumulate in the tubule which will pull water out of the body

200
Q

Salt sensitive hypertension is always associated with a ______________ of the acute pressure naturesis

A

Suppression
So kidneys will be very slow at inducing salt removal from the body

201
Q

Describe acute pressure naturesis

A

As the arterial pressure rises, in healthy individuals, the kidney will remove more and more salt to help the body remove excess fluid volume
Short term solution

202
Q

1.) Describe the changes in renal function curve for essential hypertension in NON salt sensitives.
2.) What about salt sensitive?
3.) What about people who are normotensive

A

1.) The arterial pressure will have a broader and higher pressure to reach before the kidneys start to remove sodium
2.) Blood pressure goes up as salt intake goes up & salt intake must be lowered significantly before arterial pressure lowers
3.) Smaller changes in arterial pressure will induce naturesis and the kidneys will excrete much more sodium to maintain a lowered pressure

203
Q

The passive diffusion of ____ out of all cells creates a membrane potential. This is why ____ is at higher levels inside the cell

A

K+

204
Q

What causes flaccid paralysis?

A

Too low of K+ within the cell so there is hyperpolarization that makes it harder to depolarize the cell

205
Q

What causes spastic contraction of muscle?

A

A state of hyperkalemia within the cell will slightly depolarize the cell making muscle contraction easier

206
Q

Name three systems that are put in place when there potassium levels rise and to pull potassium into the cell

A

1.) Insulin (Most imp)
2.) β adrenergic agonist
3.) Aldosterone release

207
Q

What does α-adrenergic stimulation do to potassium levels?Wah

A

Promotes movement of potassium out of the cell

208
Q

What does increased pH (alkalosis) do to potassium levels?

A

Induces K+ entry into cells in exchange for H+ to help bring pH down

209
Q

When the body is in an alkaline state, the body will go into ____________________ with ________polarization

A

Hypokalemia
Hyperpolarization

210
Q

List three types of drugs that can induce hyperkalemia

A

1.) ANG II and aldosterone inhibitors
2.) K+ sparing drugs
3.) β Blockers

211
Q

List two types of drugs that can induce hypokalemia

A

1.) K+ wasting drugs
2.) β-adrenergic agonists

212
Q

T/F: To protect against hyperkalemia, the body filters lots of K+ at the glomerulus

A

False, very little is filtered

213
Q

Where does the determination of final Urine potassium levels occur?

A

Mostly reabsorbed in the collecting duct
Some recycling at the TALH
Secretion varies at the Collecting duct

214
Q

T/F: Most potassium is reabsorbed in the kidney under normal circumstances

A

True

215
Q

Describe K+ recycling in the TALH

A

The NKCC2 channel needs to pull K+ and Na+ into the cell. Since the K+ levels are normally low in the ECF/Lumen, the ROMK channel pumps K+ out of the cell to allow the NKCC2 to function

216
Q

What is the importance of intercalated cells and where do they exist?

A

Pertain to acid base balance
In the Collecting duct

217
Q

In the intercalated cells of the CDT, exists the ______________________________ to reabsorb potassium if needed

A

K+/H+ ATPase which pushes K+ into the cell in exchange for H+

218
Q

K+ moves against or with against the concentration gradient and electrical gradient when describing the ICF

A

K+ moves down the concentration gradient from [H to L]
K+ moves down the electrical gradient from [H to L]

219
Q

Anything that promotes ____________ intracellular potassium will induce:

A

Higher concentration
K+ secretion

220
Q

What is the main hormone controlling potassium secretion

A

Aldosterone

221
Q

Does hyperkalemia or hypokalemia induce aldosterone release? Why

A

Hyperkalemia
Aldosterone will promote K+ entry into cells to pull K+ out of the plasma by stimulating Na+/K+ ATPase
Stimulates ENaC that is stimulating Na+ reabsorption from the lumen to make lumen more - to drive K+ into the lumen for excretion
Stimulates luminal potassium channels

222
Q

How does the presence of non-reabsorbable anions induce K+ secretion?
What are some examples of these non-reaborbable anions?

A

PO4 or HCO-3 in the lumen are -
This overall negative charge draws the K+ down its electrical gradient into the lumen

223
Q

What is normal total renal blood flow

A

1.2 L/min

224
Q

About how much of the cardiac output is directed to the total renal blood flow

A

25%

225
Q

Why is there a fall in blood pressure when the blood arrives at the cortical, radial, and afferent arterioles?

A

Because they are resistance vessels

226
Q

Is the glomerular a low or high resistance site? What does this mean in regard to the blood pressure?

A

Glomerulus is low resistance so there is very little reduction of blood flow along the length of the glomerular capillary

227
Q

What maintains the glomerular pressure?

A

Glomerulus has 55 mmHg because the resistance vessel, efferent arteriole, provides a backpressure

228
Q

What is EXCLUDED from the glomerular filtrate?

A

Proteins and Blood cells

229
Q

What makes anions less filterable compared to cations at the glomerulus?

A

Endothelial cells are lined with negative charges that repel the anions in the blood flow being

230
Q

What is significant about the glycocalyx?

A

Its mesh like netting that stretches across the spaces between first layer of Bowman’s capsule to prevent proteins from being filtered

231
Q

About how much of the total body weight is water?

A

60%

232
Q

About how much of the total body weight is water of the interstitial fluid?

A

40%

233
Q

About how much of the total body weight is water of the extracellular fluid?

A

20%

234
Q

Decreased ______________ and _____________ osmolality stimulate central receptors, more specifically the hypothalamus to initiate true thirst

A

Volume
Increased

235
Q

About _____% of filtered water and sodium are reabsorbed at the PCT

A

65

236
Q

Why does osmolality remain about the same as plasma osmolality at the PCT?

A

Because for each water fluid reabsorbed a salt reabsorbed with it

237
Q

Describe the movement of solutes and water in the descending loop of Henle
Does this affect osmolality?

A

No active transport
Permeable to water, reabsorption
Yes, makes the fluid in the lumen more concentrated

238
Q

Describe the movement of solutes and water in the thin ascending loop of Henle
Does this affect osmolality

A

No movement
No change in osmolality

239
Q

Why is the TALH osmolality/solute concentration drop?

A

Sodium reabsorption here which is impermeable to water

240
Q

Describe the osmolality composition at the end of the TALH

A

Osmolality is below plasma osmolality

241
Q

Describe the movement of solutes and water in the thin ascending loop of Henle
Does this affect osmolality?

A

More sodium reabsorption and impermeable to water
Yes, further reduces osmolality and become more dilute

242
Q

Where does ADH aka vasopressin act in the nephron?

A

At the collecting duct

243
Q

If there is no ADH at the collecting duct, what will happen?

A

Impermeable to water, no water reabsorption
Reabsorption of sodium via ENaC here = even more dilute urine

244
Q

ADH:
Aldosterone:

A

Water reabsorption @ collecting duct
Salt reabsorption @ collecting duct

245
Q

When there is ADH present, what will happen?

A

Collecting duct permeable to water so osmolality can be very high

246
Q

Whatever the final urine concentration and volume the following always applies:

A

The fluid entering the cortical collecting duct is always dilute relative to the plasma

247
Q

Where is the only place in the body that does not have osmotic equilibrium?

A

The kidney medulla and interstitial fluid here

248
Q

What is the countercurrent multiplication of a single event?

A

How the NKCC2 of the TALH reabsorbs sodium. Some of this sodium gets trapped in the interstitial medulla. Which is in part driven by the water that was reabsorbed in the descending loop of Henle

249
Q

When does urea recycling occur?
Where does urea recycling occur?

A

Only in the presence of ADH
Papillary collecting duct urea diffuses out
Passive inward diffusion in THIN ascending loop of Henle since some urea was trapped in the papillary interstitium

250
Q

How is the interstitial concentration gradient maintained through vasa recta blood supply?

A

The vasa recta blood flow is slow
Countercurrent exchange

251
Q

Countercurrent multiplication creates:
Countercurrent exchanger creates:

A

1.) Creates the medullary interstitial concentration gradient via tubule
2.) Maintains the concentration gradient and prevents washout via vasa recta

252
Q

Describe the counter current exchanger

A
253
Q

What is important about the countercurrent exchanger:

A

The medulla needs to be perfused with blood, but since the blood osmolarity is lower than the medulla there is risk the blood will reduce the concentration. The countercurrent exchanger prevents this

254
Q

Normally people are in danger of _______________ because of ingesting food. There is continual production of organic _______ which are metabolized to CO2 and excreted via the lungs

A

Acidosis
Acids

255
Q

__________________ are unable to get glucose into the cell for use as an energy source. So the body uses _____________metabolism that makes keto acids. This overloads the metabolic capacity at the liver which allows for accumulation of acids in the body:

A

Diabetics
lipid
Ketoacidosis

256
Q

What are fixed acids and how are they normally excreted?

A

Fixed acids made from protein metabolism
Excreted via urine

257
Q

What is the major contributor of acids in the body?
What is the minor contributor?

A

Major: organic acids from food
Minor: Fixed acids from protein metabolism

258
Q

Name the immediate body response to acid buffering

A

Rapid buffering

259
Q

Name the intermediate response to acid buffering

A

Respiratory compensation via control of the total CO2 content

260
Q

Name the long term response for acid buffering

A

Renal compensation

261
Q

What are the basic tenants of acid renal compensation

A

Removal of excess H+ and regeneration of base in form of HCO3 (bicarb)

262
Q

Describe rapid buffering

A

Ions, compound, anion proteins are circulated throughout the body and adjust within milliseconds-minutes to buffer acids that are constantly being produced

263
Q

HCO3 is an important _________________ buffer.
Negatively charged proteins buffer in _____________ and ________________
CO3 in bone provides:

A

1.) Extracellular buffer
2.) Plasma and intracellular
3.) provides an intracellular buffer store that can be released into the ECF

264
Q

Describe how acidosis can impact potassium levels

A

Potassium is normally highly concentrated within the cell
In states of low pH the H+ can be exchanged into the cell for a K+ moving outside the cell
If there is too large a reduction in intracellular K+ this will depolarize the cell wall allowing the cells to be too easily excitable and spasm and potassium excretion will be reduced at the collecting duct

265
Q

While K+/H+ buffering is an acute response to acidosis, longer term high levels of K+ will cause:

A

Stimulate release of aldosterone to encourage secretion and subsequent excretion of K+ from the principle cells of the collecting duct

266
Q

Describe the bicarbonate buffer system:

A

H+ + HCO3 ↔ H2CO3 ↔ H20 + CO2
H+ & bicarb ↔ carbonic acid ↔ H2O to CO2
Carbonic acid to water and carbon dioxide requires carbonic anhydrase for rapid breakdown

267
Q

Why can the bicarbonate buffering system via respiration be exhausted?

A

Because, the system favors CO2 production. Each time, this uses 1 H+ (good) and 1 Bicarb (HCO3 & needed)

268
Q

When plasma CO2 levels rise what will happen?

A

1.) CO2 sensitive chemoreceptors will stimulate inc. respiration
2.) The reduction in plasma pH will stimulate indirect response to inc. respiration

269
Q

How does the kidney provide long term restoration of pH balance?

A

1.) Makes bicarb HCO3
2.) Conserves HCO3 through reabsorption

270
Q

Where are sights of H+ secretion along the tubule?

A

Largely in the PCT & TALH
Minimal in the Collecting Duct

271
Q

Bicarbonate is filtered into the kidney. How is it reabosrbed?

A

H+ secretion at the PCT and TALH drives HCO3 absorption

272
Q

How does the PCT generate H+ ion to drive Na+ absorption and H+ secretion?

A

CO2 + H2O → Carbonic Acid → H+ & HCO3-
The H+ is driven out of the cell into the lumen by the Na/H+ exchanger and the HCO3- flows down its concentration gradient into the blood

273
Q

T/F: The H+ moving out of the cell drives HCO3 into the cell out of the lumen of the PCT & TALH

A

False, there is no mechanism for HCO3, that was filtered through the glomerulus into the lumen, to be directly absorbed into the cell
The Bicarb that is absorbed here is generated intracellularly

274
Q

Describe HCO3 reabsorption mechanism at the TALH and PCT

A

The H+ that is excreted into the lumen combines with the HCO3- of the filtrate
This forms carbonic acid, H2CO3-
There is carbonic anhydrase lining the luminal cell membrane.
This converts the the carbonic acid into H20 & CO2 which can diffuse into the cell to make HCO3 INTRAcellularly

275
Q

T/F: The mechanism to reabsorb Bicarb at the TALH and PCT is saturable

A

True

276
Q

What is different about the HCO3 regeneration at the Collecting duct compared to TALH & PCT? (2)

A

1.) There is no carbonic anhydrase at the brush border of the luminal side of the cell so converting the Bicarb & H+ to H20 & CO2 is fairly slow in the collecting duct
2.) Since the majority of the bicarb is gone by the time reaching the collecting duct, the H+ will need to combine with a different buffer. Some of that includes HPO4

277
Q

What is different about the H+ secretion at the Collecting duct compared to TALH & PCT?

A

H+ ion enters via H+/ATPse or by H+/K+ ATPase

278
Q

Nephrogenic diabetes insipidus means:
How does this affect plasma and urine osmolality

A

The collecting duct cannot reabsorb water
Plasma osmolality high
Urine osmolality low

279
Q

Low pCO2 causes:

A

Alkalosis `

280
Q

How to calculate the GFR?

A

[ Urine inulin / Plasma Inulin ] * Urine flow = mL/min

281
Q

How to calculate est. Renal Plasma Flow

A

[ Urine of substance mg/mL / Plasma of substance mg/mL ] * Urine flow = mL / min

282
Q

How to calculate the filtration fraction and what is it?

A

The fraction of the renal plasma flow filtered across the glomerulus
GFR / RPF

283
Q

What is used to calculate the renal plasma flow? Any why is it used?

A

PAH, Because it is almost entirely cleared from plasma during 1 pass through the kidney

284
Q

While 99% of protein is not filtered through the glomerulus, what about the 1% that makes it to the tubule?

A

Once the protein reaches the collecting duct, the proteins are absorbed, degraded within the cell to AA that are returned to the circulation via peritubular capillar

285
Q

When there is heavy proteinuria, what happens to the plasma protein level?

A

The liver cannot synthesize enough protein and plasma protein goes down

285
Q

Hydrostatic pressure of the blood causes:
Colloid osmotic pressure (aka oncotic pressure) of the proteins causes:

A

Filtration (moving fluid out)
Absorption from the ECF

286
Q

When proteinuria occurs, how does this affect the colloid osmotic pressure (oncotic pressure)

A

The subsequent plasma protein fall lower the colloid osmotic pressure that disallows absorption of ECF and can cause edema

287
Q

In the capillary, there are driving pressure acting across the wall of capillary, hydrostatic pressure:
Colloid osmotic pressure:

A

Fluid pressure of blood trying to push water OUT
Due to plasma protein trapped inside the capillary trying to pull water IN

288
Q

At the arterial end of a capillary the pressure is normally ___________. Why?

A

To force water nutrients out and into interstitial space

289
Q

As blood moves down the capillary, hydrostatic pressure _______________ and loss of water by filtration at this point causes the colloid osmotic pressure to ______________. This allows:

A

Falls
Rises
Uptake of fluid from the interstitial to deliver waste products

290
Q

Glomerular blood pressure is ___________ at ~ 55 mgHg.
Since Bowman’s capsule is fluid filled:
The difference between P glomerulus capillary - Pressure Bowmans capsule does what?

A

High
It exerts a pressure back ~ 10 mmHg
Drives and determines filtration

291
Q

What is the glomerular oncotic pressure ( colloid osmotic, )?
What is the Bowman’s colloid osmotic pressure?

A

1.) The pressure exerted by proteins of the plasma that increases moving from afferent to efferent arteriole due to the loss of water
2.) There is no colloid osmotic pressure in Bowman’s space since no protein is filtered through the glomerulus

292
Q

T/F: The pressure lowers are the blood moves through the glomerular capillary because the water is filtered out and volume decreases

A

False, because the vessel is low resistance the pressure stays the same

293
Q

When does filtration cease as plasma flows through the glomerular capillary?

A

When the [Pgc - P bs] aka ΔP is EQUAL to the oncotic pressure of the glomerular capillary moving towards the efferent arteriole as water is filtered into the tubule
Filtration is = Absorption

294
Q

The greater the renal plasma flow:

A

The greater the glomerular filtration rate

295
Q

What is the filtration fraction?

A

The percentage of water that is driven out of the renal plasma flow as it passes through the kidney

296
Q

Why does increasing filtration fraction increase the GFR without changing the renal plasma flow?

A

The same amount of plasma is flowing but if more water is being filtered out and into the glomerulus, then the glomerular filtration rate will increase

297
Q

Changes in GFR can be regulated by:

A

Renal plasma flow
Fraction filtration
or both

298
Q

What is the MOST important component effecting GFR?

A

Renal plasma flow because at lower volume of plasma being delivered to the glomerulus allows the oncotic pressure and hydrostatic pressure to be equalized sooner

299
Q

Renal plasma flow is controlled by changes in:

A

Afferent and efferent arteriolar resistance

300
Q

Relaxation of renal afferent and or renal efferent arterioles will:
Why?

A

Increase RPF
Both are relaxed so flow increases

301
Q

If afferent artiole resistance increases, what happens to the Pressure of the glomerular capillary?

A

Pressure drops

302
Q

If efferent arteriole resistance increase what happens to the Pressure at the glomerular capillary?

A

Glomerular pressure rises because there is back pressure onto the glomerular capillary

303
Q

If there is increased resistance of afferent and efferent arterioles, what happens to glomerular capillary pressure?

A

Nothing, since the changes are same on start and end

304
Q

What is Kf and why is it significant?

A

Kf = filtration surface area * water permeability
It can influence glomerular filtration rate

305
Q

Tone in the ___________ ______________ ______ determines Kf via regulation of glomerular filtration SA. Normally these are relaxed so Kf is high enough so that it doesn’t influence GFR much

A

Glomerular mesangial cells

306
Q

Normally renal nerve activity is low. What happens when renal nerves are stimulated?
What normally stimulates renal nerve activity?

A

Overall lowered GFR. The nerves cause constriction of afferent and efferent vessels, such that renal plasma flow is reduced and thus GFR is released
Stimulated by low volume/Low BP or need to reduce GFR

307
Q

How does Ang II at higher levels raise Pressure of the glomerular capillary?

A

The Ang II vasoconstricts both afferent and efferent capillaries but prefers the efferent capillary. This increased resistance places back pressure on the glomerular capillary and causes increased Pressure at glomerular capillary when blood pressure is reduced

308
Q

What does increased nitric oxide do?

A

Vasodilates the afferent and efferent vessels and relaxes the mesangial cells to raise RPF and thus raising GFR

309
Q

Why are COX inhibitors need to be used with caution in older adults?

A

With age, GFR naturally falls.
To supplement, prostaglandins vasodilate to help raise GFR
Thus if using COX (a type of prostaglandin) inhibitor this can decrease GFR further

310
Q

ANP is a ________________ and has _________________ effects. How does it work?

A

Vasodilator
Natriuretic (increase sodium excretion)
Dilates afferent artiole increasing Pressure of glomerular capillary and plasma flow = Inc GFR & inhibits sodium reabsorption

311
Q

________ _____________ ____________ & ____________________ causes vasdoilation of both afferent and efferent resistance, thus increasing RPF & GFR

A

High dietary protein
Pregnancy

312
Q

How does the kidney maintain constant GFR in the setting of fluctuating BP?

A

In heightened BP, the afferent arteriole constricts to maintain to maintain RPF and pressure of glomerular capillary

313
Q

Name the two mechanisms of renal autoregulation

A

1.) Myogenic mechanism-fast requiring no nerve input
2.) Tubuloglomerular feedback

314
Q

What is tubuloglomerular feedback?

A

A form of renal autoregulation at the juxtoglomerular appratus where the macula densa in the TALH and DCT contacts with the afferent arteriole

315
Q

Renal blood flow supplies oxygen for renal metabolism. Renal O2 utilization is regulated according to energy requirement. What is the main energy requiring process in the kidney?

A

Active sodium reabsorption at the tubules

316
Q

Why is it that oxygen extraction stays the same with increased Na absorption despite it being a large energy requiring event.

A

Increased Na absorption is equivalent to inc. GFR and RPF
Thus, while more O2 is needed and being extracted from the blood, more O2 overall is being delivered so the extraction matches what is being delivered

317
Q

As GFR ___________________ the plasma creatinine _________________. The normal plasma creatinine is normally:

A

Falls
Increases
Normally plasma creatinine is low

318
Q

What is a contributing factor to progressive glomerular injury?

A

Long term increased glomerular pressure damages glomerular capillary

319
Q

Why are ACE inhibitors considered to be renal protecting?

A

Because they inhibit ANG
The continuous elevation of ANG will vasoconstrict to raise pressure of glomerular capillary and damage it leading to CKD

Med Physiology Certificate (4 decks)

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