Unit 4: Renal Phys.-- Sodium and Potassium Balance

Question 1

What is the most important function of the kidney? Why?

Answer 1

reabsorption of Na+ b/c all reabsorption is tied to it and it helps regulate BP

Question 2

What is responsible for maintaining a normal Na+ concentration in the body?

Answer 2

the kidneys

Question 3

What does it mean if there is a positive Na+ balance?

What if there is a negative Na+ balance?

Answer 3

positive–> excretion is less than intake and accumulate Na+

negative–> excretion is greater than intake–> will be deficient in Na+

Question 4

When we have a positive Na+ balance, where does the excess Na+ primarily accumulate? What does this lead to?

Answer 4

in ECF–> leads to ECF volume expansion –> which will increase BV and BP

may be assoc. with edema

Question 5

When we have a negative Na+ balance, where is excess Na+ primarily lost from? What does this lead to?

Answer 5

primarily from ECF–> leads to ECF volume contraction –> decreases BV and BP

Question 6

Where is the majority of our body K+?

Answer 6

ICF - 98%

ECF- 2%

Question 7

What type of effect will a small shift of K+ into or out of our cells have?

Answer 7

cause a large change in K+ conc. in ECF

shifts always have a greater impact on K+ ECF conc.

Question 8

How is the large differential of K+ in ICF and in ECF maintained?

Answer 8

via the Na+-K+ ATPase pump

3 Na+ out
2 K+ in

Question 9

What is the major cation taht exchanges for H+?

Answer 9

K+

Question 10

What may cause a shift of K+ from ICF –> ECF?

Answer 10

• insulin deficiency
• beta2-adrenergic antagonists
• alpha-adrenergic agonists
• acidosis
• hyperosmolarity in ECF
• cell lysis
• exercise

Question 11

What may cause a shift of K+ from ECF –> ICF?

Answer 11

• insulin
• beta2-adrenergic agonists (NE)
• alpha-adrenergic antagonists (Beta blocker)
• alkalosis
• hyposmolarity

Question 12

What effect does insulin have on the Na+K+ pump? Why is this important?

Answer 12

increases activity of it –> helps move ingested K+ into cells after a meal

prevents hyperkalemia after K+ rich meal

Question 13

What will high levels of insulin cause involving K+? What would type I diabetes cause?

Answer 13

high levels of insulin–> hypokalemia ( less than 2 mEq/L)

type I diabetes–> hyperkalemia (more than 5 mEq/L

(normal levels are ~4.5 mEq/L)

Question 14

What are acid-base abnormalities often associated with?

Answer 14

K+ abnormalities

Question 15

What is the term for low H+ conc. in the blood? What will the cause to happen?

Answer 15

Alkalemia
will cause:
- H+ (from cells)–> to ECF
- K+ from ECF –> into cells, ICF (creates hypokalemia)

Question 16

What is the term for high H+ conc. in the blood? What will this cause to happen?

Answer 16

Acidemia

• H+ (from blood)–> into ICF
• K+ from cells –> into ECF (creates hyperkalemia)

Question 17

K+ disturbances only occur in certain metabolic acidosis or alkalosis. What may these cases be?

Answer 17

• effect HCO3- and H+
• excess of organic acid (lactic acid, ketoacids, salicylic acid)
• –they will enter cell in exchange for H+ and no need for K+ exchange

Question 18

In what acid-base abnormalities do K+ disturbances not occur?

Answer 18

respiratory acidosis or alkalosis
–> these are due to change in CO2 which is lipid soluble and diffuse across membrane w/o effecting K+ ( no need to move K+ to maintain electrical neutrality)

Question 19

What will activation of beta2 adrenergic receptors have on the Na+K+ ATPase?

1. What do Beta2 agonists cause?
2. What do Beta2 antagonists cause?

Answer 19

increase activity of it (pump more K+ into cell)

1. hypokalemia
2. hyperkalemia

Question 20

What will activation of alpha- adrenergic receptors have on K+?

1. What do alpha-agonist cause?
2. What do alpha antagonists cause?

Answer 20

shift K+ out of cells

1. hyperkalemia
2. hypokalemia

Question 21

What will an increase is osmolarity in ECF cause K+ to do?

Answer 21

K+ to move out of cells (b/c water will flow out and increase K+ conc. in cell and therefore want to drag K+ out of cell too

Question 22

What effect will cell lysis have on K+? What are examples of what may cause this?

Answer 22

will dump K+ into ECF–> cause hyperkelemia

Ex: burn, rhabdomyolysis, chemotherapy, fresh water drowing**

Question 23

What impact will fresh water drowning have on our cells?

Answer 23

cause them to burst–> release K+ into ECF (due to take on water from lungs and now water wants to rush into cells and they burst)

Question 24

How does K+ shift during exercise? What impact will this have on blood vessels?

Answer 24

K+ shifts out of cells due to depletion of cellular ATP stores that will open K+ channels

K+ shift out of cells acts as local vasodilator helping to increase blood flow to exercising muscle

Question 25

How is the External K+ balance kept in check?

Answer 25

kidneys play a role

output = intake

Question 26

How much of K+ is filtered? Why?

Answer 26

K+ is FREELY filtered at glomerular capillaries due to NOT being bound to anything

filtered load of K+ = GFR x plasma conc. of K+

Question 27

Where does most of the reabsorption of K+ take place? How much is it?

Where else is K+ reabsorbed? via what?

Where is the final adjustment of K+ secretion made?

Answer 27

In Proximal Convoluted Tubule–> 67%

Thick ascending limb–> 20% (via Na+-K+-2Cl- cotransporter)

Distal Tubule and Collecting duct (in response to dietary change)

Question 28

What cells are responsible for reabsorption of K+?

Answer 28

alpha-intercalated cells in collecting ducts (less common) via luminal H+-K+ ATPase

Question 29

What cells are responsible for secretion of K+? What may this be due to?

Answer 29

principle cells (more common)

• use Na+K+ ATPase on Basolateral side to pump for K+ in and…
• then passive diffusion occurs on luminal side to secrete K+

Due to:

• increase dietary K+
• increase Aldosterone

Question 30

What effect will an increase in Aldosterone have on K+ secretion and how?

Answer 30

secrete it for by principle cells by:

• increase quantity of Na+ and K+ channels on luminal side
• increase quantity of Na+ K+ ATPase on basolateral side

Question 31

What ion has the greatest variability with excretion?

Answer 31

K+

Question 32

What effect will Alkalosis have of K+ secretion?

Answer 32

increase K+ secretion–> lead to hypokalemia

(a decrease in H+ ECF conc. –> causes H+ to leave vells and K+ to enter cell–> increasing driving force for K+ secretion)

Question 33

What effect will Acidosis have on K+ secretion?

Answer 33

decreases K+ secretion–> lead to hyperkalemia

increase in H+ ECF conc.–> causes H+ to enter cell and K+ to leave cell–> decreasing driving force for K+ secretion

Question 34

How will Diuretics–Lopp diuretics and thiazide diuretics–effect K+ secretion?

What will the loop diuretics also do?

Answer 34

will increase K+ excretion –> leading to hypokalemia

loop diuretics will also inhibit Na+K+2Cl- costransporter
cause kaliuresis and hypokalemia

Question 35

What effect will K+ sparing Diuretics have on K+ secretion?

Answer 35

inhibit action of aldosterone (which + secretion of K+) on principle cells –> therefore inhibit K+ secretion

(do not cause kaliuresis and hypokalemia)

Question 36

How will large anions in the luminal fluid (like sulface and HCO3-) effect K+ secretion?

Answer 36

promote K+ secretion

they are negative charged and attracted positive ions