Regulation of Na and H20 Balance

Question 1

What is the main substance exerting osmotic pressure in the Cell? In the Interstitial Fluid? In the plasma?

Answer 1

K = Cells
Na = interstitial fluid
Protein = plasma

Question 2

Where does reabsorption of filtered Na load mainly occur?

Answer 2

PCT

Question 3

What part of the nephron is Na reabsorption regulated?

Answer 3

DCT controls how much Na gets out.

Question 4

What are three neurohumoral factors that control renal Na reabsorption?

Answer 4

1. Activation of renal sympathetic nerves
2. Activation of renin/ang system
3. secretion of aldosterone

Question 5

What are some neurohumoral factors that promote Na excretion?

Answer 5

1. release of atrial/brain natriuretic peptides
2. Release of urodilatin
3. Intrarenal prostalgandins

Question 6

With increased activity of renal sympathetic nerves, what are some results?

Answer 6

1. decrease GFR (clamp down on afferent) –> decrease fluid delivery to macula densa –> increase renin secretion
2. Increase PCT reabsoprtion of Na and H20
3. Direct stimulation of JG cells via beta adrenergic to increase renin secretion

Question 7

What are some factors that promote renin secretion?

Answer 7

1. renal sympathetic stimulation
2. tubulogloermular feedback
3. intrarenal baroreceptor (walls of afferent which constrict and the decreased pressure on the JG cells release renin.

Question 8

What effect would a loop diuretics have on renin secretion?

Answer 8

Stimulate renin secretion

Question 9

What transporter/pump does loop diuretics inhibit?

Answer 9

Na/K/Cl cotransporter

Question 10

T or F: Ang II stimulates systemic arteiolar constriction.

Answer 10

True

Question 11

Which arteriole does Ang II have greater effect?

Answer 11

Efferent

Question 12

What parts of the nephron does Ang II have it’s greatest effect to promote Na reabsorption and via what channel?

Answer 12

PCT via the Na/H exchanger.

Question 13

Ang II promotes 1 in the hypothalamus, 2 in posterior pituitary, and 3 in the adrenal cortex.

Answer 13

1. Thirst
2. ADH
3. Aldosterone

Question 14

T or F, Ang II has no effect on glomerular mesangial cell.

Answer 14

F. Ang II contrast glomerular mesangial cell and thus decreasing capiillary surface area for filtration and thus decreases filtration which decreased medullary blood flow and increased tubularNa reabsorption and thus retain more sodium.

Question 15

Where does aldosterone have it’s effect?

Answer 15

DCT and principal cells of Collect duct

Question 16

Under Ang II stimulation, Na is reabsorbed thus making the luminal fluid more negative. what helps to neutralize it?

Answer 16

Passive Cl- reabsorption to neutralize inside the cell, and K/H secretion in the lumen.

Question 17

Aldoesterone caues Principal cells to secrete what ion?

Answer 17

K+

Question 18

What effect do intercalated cells have on H+

Answer 18

Secrete H+ at the CCD

Question 19

In a person with hyperaldosteronism what happens to their k levels?

Answer 19

Patient becomes Hypokalemic since they’re losing K and retain Na. They also become alkalotic since they’re also losing H+.

Question 20

Typical presentation of hyperaldosteronism are?

Answer 20

Hypokalemia and metabolic alkalosis.

Question 21

Factors controlling aldosterone secretion are _?

Answer 21

1. Increased plasma K
2. Increased plasma ACTH
3. Volume depletion which leads to increased plasma ang II

Question 22

What is the feedback control of aldosterone secretion.

Answer 22

With increased aldosterone, more Na and water is retained and thus increases ECF and increases mean renal atrial pressure and thus decrease discharge of renal nerves and feedbacks to JG apparatus to inhibit renin release.

Question 23

Name some effects of ANP.

Answer 23

1. increase GFR
2. Inhibit Na reabsorption in medullary collecting duct
3. ANP suppresses renin secretion
4. suppress aldosterone secretion
5. systemic vasodilation
6. suppresses ADH secretion actions

Question 24

Four ways to decrease circulating blood volume are?

Answer 24

1. Decrease ADH secretion
2. Release ANP
3. Decrease renal nerve discharge
4. Increase heart rate.

Question 25

What is the endogneous renal natriuretic peptide called?

Answer 25

Urodilatin

Question 26

What cells releases Urodilatin?

Answer 26

cells of the DCT and collecting duct

Question 27

what effect does intrarenal prostalandins have on Na?

Answer 27

Increases Na excretion

Question 28

What effect does prostaglandins have on medullary gradient?

Answer 28

Concentration of the intersitum goes down –> decrease osmolarity

Question 29

What two major stimuli releases ADH?

Answer 29

1. Change in hyperosmolality

2. Volume depletion

Question 30

Where are osmoreceptors located?

Answer 30

1. hypothalamus

2. liver

Question 31

At normal baseline, how much ADH is being released?

Answer 31

Maximal secretion of ADH

Question 32

If osmolality increases beyond the normal level, what is the way way to fix it?

Answer 32

Increase thirst.

Question 33

When your plasma osmolality falls, what happens to your ADH level?

Answer 33

ADH release is inhibited with decreased osmolality.

Question 34

Name three main series of events that responds to increased ECF.

Answer 34

1. Decrease sympathetic outflow to kidney (dilate afferent; decrease PCT NaCl reabsoption; increase NaCl excretion.
2. Increase ANP - inhibit aldosterone
3. Decrease renin secretion, thus aldosterone

Question 35

Complete the following:
Too much water --> _1_
Too little water --> _2_
Too much Na --> _3_
Too little Na --> _4_

Answer 35

1. Hyponatremia
2. Hypernatremia
3. Edema
4. Volume depletion

Question 36

During hypovolemia what percentage of Na is reabsorbed in the PCT vs. normal?

Answer 36

80% during hypovolemia compared to 67% during normal.

Question 37

What happens to fractional excretion during dehydration? Hemorrhage? Hypovolemia?

Answer 37

FE decreases for all.