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Flashcards in Renal regulation of K and Ca Deck (51)
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1

The vast majority of body potassium is located

In the cells
- is the most important intracellular ion

2

Potassium output

- urine: 92 mEq/d
- feces: 8 mEq/d
- total: 100 mEq/d

3

Partitioning of Na and K across cell membrane allows for

Polarity differences that are critical for excitable membranes and the development of action potentials

4

Intracellular dehydration

Due to loss or lack of intake leading to long term potassium wasting

5

How does urinary excretion of potassium range from 1 - over 100% of what was filtered at the glomerulus?

Tubules can reabsorb almost all of what was filtered to actually secreting extra potassium into the tubule on top of what was filtered

6

Plasma potassium only represents _____

A small fraction of whole body potassium

7

How to assess overall body potassium status

Measure renal potassium fractional excretion
- asses proportion of potassium filtered across the glomerulus compared to that contained in the urine

8

Causes of extracellular K moving into the cell

- increases K intake
- insulin
- aldosterone
- beta-adrenergic
- alkalosis

9

Causes of intracellular K moving out of the cell

- cell lysis
- strenuous exercise
- acidosis
- beta blockade
- HYPP

10

Insulin

Insulin surge after eating moves excess K just ingested from the ECF into the cell

11

____ and ____ tend to push K into cells

Insulin; alkalosis

12

Giving IV bicarb causes H ions to move out of the cells to maintain normal pH, and K moves _____ to maintain an electroneutral exchange of ions

Into cells

13

Cellular acidosis

Results in K moving out of the cell to maintain electroneutrality within the cell and reduce K uptake into the cell by decreasing the efficiency of the Na K ATPase pump

14

Patients that are inappetent and suffering from GI electrolyte losses are _____

In a negative potassium balance

15

The ______ is responsible for long term sustainable control of potassium

Kidney

16

Potassium excretion is determined by the sum of 3 renal processes:

- rate of filtration
- tubular K reabsorption/secretion
- tubular flow rate

17

Acute renal failure

Results in a decrease in GFR and can cause serious K accumulation and hyperkalemia due to a high potassium diet

18

What is the primary cell involved in potassium excretion?

Principal cells of the late distal and collecting tubules

19

What is the limiting factor of the Na K ATPase pump?

Electrolyte availability, NOT energy!

20

Aldosterone secretion is increased by

Increased serum potassium
- independent of angiotensin 2
- causes increased secretion of K into the distal tubule lumen by the principle cells

21

Where is the primary site of aldosterone?

On the principle cells of the cortical collecting tubule

22

Aldosterone feedback loop

Increased K intake --> increased plasma K concentration ---> increased aldosterone (+) --> increased K secretion cortical collecting tubules --> increased K excretion

23

What happens to K in the absence of aldosterone secretion?

Renal secretion of K is impaired, leading to ECF potassium concentration to rise to high levels

24

What happens to K with excess aldosterone secretion?

Potassium secretion becomes greatly increased, causing potassium loss by the kidneys = hypokalemia

25

Does decreased aldosterone secretion due to a Na rich diet lead to K retention?

No, effects are counterbalanced by increased flow rate, which moves any filtered K downstream fast enough that there is a minimal build up of K within the lumen

26

An increase in distal tubular flow rate (due to volume expansion, high Na intake, etc) stimulates potassium _____

Secretion

27

A decrease in distal tubular flow rate (caused by sodium depletion) leads to _______

Reduced K secretion

28

The effect of tubular flow rate on K secretion is the distal and collecting tubules is strongly influenced by _______

Potassium intake

29

The principle cell apical membrane contains ________

Unregulated K channels

30

Intercalated type A cells are able to actively pump _____ out against a high concentration gradient

H ions
- function to reabsorb K