Jan4 M2-Sodium Homeostasis

Question 1

what’s the cause for the variations in our U Na

Answer 1

changes in dietary Na intake

Question 2

what senses body sodium

Answer 2

PRESSURE receptors in the vascular wall, the renal AA and the heart

Question 3

pressure receptors (baroreceptors) activation leads to changes in what

Answer 3

RAAS, SS, ADH and ANPs

Question 4

impact of SS activation on the kidney (2)

Answer 4

SS stimulates juxtaglomerular cells to secrete renin

NE stimulates Na reabso in the PCT

Question 5

diuretics mainly for what 2 conditions

Answer 5

edema and hypertension

Question 6

Na in the PCT: %, mechanisms (3) and regulatory factors (3)

Answer 6

65%. Na channels + Na-H exchange + NaK ATPase drives Na+glucose,a.a,PO4 cotransporters.
AT2, NE and GFR

Question 7

Na in loop of Henle: %, mechanisms (3) and regulatory factor

Answer 7

No reabso in the DL. TAL: 25%. NaK ATPase (baso), Na-K-2Cl cotransporter, Na-H exchanger, paracellular (tight junctions). flow-dependent

Question 8

Na in the DCT: %, mechanism and regulatory factor

Answer 8

5%. NaK ATPase (baso), Na-Cl cotransporter. flow-dependent

Question 9

Na in the collecting tubules: %, mechanism and regulatory factors (2)

Answer 9

3%, Na channels. aldo and ANP

Question 10

other ion coming in with Na in CCD (CT) and how

Answer 10

Cl- paracellularly bc cation needs its anion

Question 11

what goes outside CT to compensate on Na entry and how

Answer 11

K through K channel

Question 12

aldosterone: hormone type, exact mode of action and on what exact cell

Answer 12

steroid hormone, binds aldoR in the nucleus of principal cells (CCD). aldoR acts as TF. more Na and K channels are made

Question 13

AT2 and NE exact mode of action on the tubule in volume depletion

Answer 13

enhance Na reabso in PCT by increasing the activity of the Na-H exchanger

Question 14

feedback loop in the RAAS

Answer 14

aldosterone feeds back on renin and suppresses it (baroreceptor feedback)

Question 15

aldo produced where exactly, stimulus for its release and what exact molecule stimulates it + exact site of action of aldo

Answer 15

hypovolemia and AT2. zona glomerulosa. acts on CCD (CT)

Question 16

aldo makes Na reabso vary by how much

Answer 16

0 to 2%. no aldo. 2% filtered load is excreted. with aldo: 0% filtered load is excreted

Question 17

adrenal layers + fct and which are in cortex/medulla

Answer 17

cortex: zona glomerulosa (salt), zona fasciculata (sugar), zona reticularis (sex)
medulla: panic (catecholamines)

Question 18

3 mechanisms by which renin is stimulated in hypovolemia

Answer 18

SS activity, drop in arterial P (less stretch on AA), less NaCl delivery to the macula densa

Question 19

why does Na = volume

Answer 19

it is the main extracellular ion

Question 20

2 things doing the opposite of aldo on Na excretion (2 other factors)

Answer 20

ANP and BP

Question 21

how ANP acts to increase Na excretion (3)

Answer 21

• acts on CT (CCD) to stop eNac channels and decrease Na reabso
• GFR (AA dilation and EA constriction)
• inhibits aldo release

Question 22

how BP acts on increase Na excretion

Answer 22

pressure natriuresis

Question 23

what’s the result if all ingested Na is not excreted

Answer 23

increase in ECF volume (interstitial and intravascular)

Question 24

what happens to IV volume if give 1L saline and why

Answer 24

increases by 250 ml because Na can’t cross cells. extra Na to the body always in ECF. contributes to ECF volume

Question 25

good strategy to control BP

Answer 25

lower dietary Na intake

Question 26

euvolemic % Na reabso in the tubule

Answer 26

PCT: 65%
TAL: 25%
DCT: 5%
CCD: 3% 
1% excreted

Question 27

main changes in tubular Na reabso in hypovolemia

Answer 27

• 80% abso in PCT (AT2 and NE enhance Na-H exchanger)

- 0% excreted

Question 28

main changes in tubular Na reabso in hypervolemia

Answer 28

50% reabso PCT
12% reabso DCT
6% excreted

Question 29

4 volume regulation systems

Answer 29

SS, RAAS, ANPs, ADH

Question 30

SS effects on kidneys in very low BP (severe hemorrhage, severe hypovolemia, ..)

Answer 30

• constricts renal arterioles to drop GFR (overrides renal autoregulation (of GFR))
• activates renin (RAAS)

Question 31

tubules reaction in severe drop in BP

Answer 31

increase Na reabsorption