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Physiology > K Regulation > Flashcards

K Regulation Flashcards

1
Q

What is renal secretion?

A

moving a substance from the blood into the lumen of a nephron

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2
Q

What is the mechanism through which secretion of substances takes place?

A

Active pumps on the basolateral side of the nephron tubule cell, establishing a gradient (high inside cell)

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3
Q

Apical part of a lumen cell = ? Basolateral = ?

A

Apical = The part that faces the tubule lumen

Basolateral = the part that faces the interstitium

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4
Q

Secretion of organic cations through the tubule cell is different from secretion of organic anions. Why?

A

Since the electrical force on the ion from the negative membrane potential favors movement of the cation into the cell, from the interstitial fluid.

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5
Q

What is the significance of the fact that many molecules in the blood use the same transporter to be secreted into the lumen of the nephron?

A

secretion of one substance might be decreased in the presence of one of its competitions for the carrier protein

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6
Q

Why is it that a substance that is secreted may not always stay in the tubular lumen? (2)

A

There can be back leak through the “tight” junctions

pH of urine can affect charge, and thus solubility of substance

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7
Q

What happens with ASA when the urine is highly acidic (as in acidemia)?

A

Since ASA is an organic acid, low pH will protonate it, and cause it to leak back in

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8
Q

How can you treat overdose on ASA via the renal tubules?

A

Give lots of bicarb

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9
Q

Organic cations are also called what?

A

Organic bases

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10
Q

If the dissociated state of an organic base predominates, what will predominate: excretion or reabsorption?

A

Excretion

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11
Q

Acidification of urine increases or decreases reabsorption of organic bases?

A

decreases

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12
Q

What are atropine, morphine and cimetidine–organic acids or bases?

A

Organic bases

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13
Q

Excretion = ?

A

Secretion + filtration

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14
Q

Why is PAH used to demonstrate renal plasma flow?

A

For the most part, it mostly cannot reabsorbed, only filtered and secreted

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15
Q

What is the point at which the renal nephrons secrete the maximum amount of a substance?

A

Transport maximum

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16
Q

What is the equation for renal plasma flow?

A

[(Upah)(V) / Ppah ]/ (1-hematocrit)

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17
Q

Why isn’t PAH perfect?

A

Some is absorbed from the nephron

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18
Q

How do you calculate the filtration fraction?

A

GFR/ ERFP

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19
Q

What is the filtration fraction?

A

The percent of the plasma delivered to the kidneys that is filtered

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20
Q

Why is K so important to homeostasis?

A

Establishes membrane potentials (like in the heart)

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21
Q

Is K bound to plasma proteins? What is the consequence of this?

A

No, thus it is freely filtered at the glomerulus

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22
Q

Where does most K reabsorption take place? How regulated is this?

A

Ascending loop of Henle

Essentially unregulated

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23
Q

What/where are the regulated parts of K reabsorption?

A

Distal tubule and collecting duct

24
Q

What happens to the tubules in hyperkalemia?

A

High K+ stimulates the Na/K+ATPase pump on basolateral surface. This transports K+ into the tubule cell. K+ can then flow down its electrochemical gradient through open K+ channels in the luminal membrane.

25
Q

What is the chemical that stimulates K secretion (besides K itself)?

A

Aldosterone

26
Q

What happens to the renal tubule in hypokalemia?

A

the Na+/K+ATPase pump is inhibited. The collecting duct intercalated cells have a K+ resorption pump on their luminal membrane and this pump is continually active.

27
Q

True or false: The collecting duct intercalated cells have a K+ resorption pump on their luminal membrane and this pump is continually active. Only the Na/K pump on the basolateral surface of tubule cells are regulated

A

True

28
Q

What is the main effect of aldosterone on K reuptake/secretion?

A

increase the number of active epithelial sodium channels (ENaCs) in the collecting ducts, increasing the reabsorption of Na+ and increase the secretion of K+.

29
Q

What is the effect of ANP on ENaC? What is the effect on plasma [K]?

A

Inhibited, leading to increased [K]

30
Q

In what cells are the Na/K pumps regulated within a nephron?

A

Principle cells

31
Q

What are the two ways discussed in lecture that increases aldosterone production?

A
  1. Increased plasma [K]

2. Activation of renin-angiotensin system

32
Q

What are the five effects of aldosterone?

A
  1. Increase the amount of Na/K-ATPase in the basolateral membrane
  2. Increase expression of EnaC in apical membrane
  3. Elevate SGK1 to further 1 and 2
  4. Stimulates CAP1 to activate ENaC
  5. Increases K channels
33
Q

What is the effect of ouabain?

A

inhibits Na/K pump

34
Q

What is the effect of a diuretic? What does this do to K secretion?

A

inhibits the reabsorption of water at some point in the nephron, causing water and K to be secreted

35
Q

What is the effect of loop diuretics?

A

Block the Na/K/Cl pumps in the thick ascending loop of Henle on the luminal side. This leads to a decrease in water reabsorption, because there is a lower gradient of solutes

36
Q

What lab value (discussed in this lecture specifically) should be closely monitored with patients on diuretics?

A

[K]

37
Q

What is the MOA of thiazide diuretics?

A

inhibit NaCl reabsorption in the early distal tubule, thus inhibiting water following

38
Q

What causes the increase in K secretion to increased flow?

A

Cilia bending causes cascade to be activated, Ca activation, and K channels recruited

39
Q

What are the potassium sparing diuretics? How do they work?

A

Aldosterone inhibitors, which will decrease Na and water reabsorption

40
Q

What is a complication of using aldosterone inhibitors?

A

Hyperkalemia

41
Q

What is the effect of metabolic alkalosis on the Na/K ATPase on the basolateral membrane of principal cells of the late distal convoluted tubule and collecting ducts? What happens to the intracellular [K]?

A

Increases x2

42
Q

What are the three loop diuretics?

A

Furosemide
Ethacrynic acid
Bumetaide

43
Q

Which side of the principal cells is the Na/K ATPase on: the basolateral or the luminal side?

A

Basolateral

44
Q

Why does the reabsorption of other positive ions decrease in response to the presence of loop diuretics?

A

The drug lowers the positive Electrochemical gradient in the lumen

45
Q

What is the major source of K loss in the nephrons: the inactivation of the pump or the increase flow, leading to increased K excretion

A

Increased flow

46
Q

What causes the increased K excretion seen in metabolic alkalosis?

A

Increases the Na/K ATPase action in the distal tubule, increasing K intake into the cell from the ECF, and thus causing it to flow into the lumen

47
Q

Chronic metabolic alkalosis + decreased ECF results in a significant increase in K excretion. Why?

A

Increases aldosterone d/t lower BP. This activates the Na/K pump

48
Q

What is the effect of acidosis on [K]? How?

A

Sometimes causes hyperkalemia.

Caused by an intake of H into cells, leading to outflow of K to maintain electric neutrality

49
Q

What is the effect of aldosterone on K secretion? How?

A

Increases via increasing the Na/K pump action

50
Q

What controls secretion of aldosterone?

A

plasma [K]

51
Q

What is Conn syndrome, and how does it relate to K secretion?

A

Causes excess aldosterone, thus increases K secretion

52
Q

What is Addison’s disease, and how can it cause Hyperkalemia?

A

Inhibition of aldosterone, leading to less function of the Na/K pump

53
Q

What is the effect of beta blockers on K?

A

May cause hyperkalemia

54
Q

What is the effect of catecholamines on plasma [K]?

A

Hypokalemia

55
Q

What is the main cell type that is involved in K regulation?

A

Principle cells of the distal tubule

56
Q

What are the three ways that an increased plasma [K] will increase K secretion?

A
  1. Increases Na/K ATPase activity
  2. Increased gradient potential
  3. Increased aldosterone synthesis

Physiology (75 decks)

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