Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Renal Physiology > Salt Balance > Flashcards

Salt Balance Flashcards

1
Q

Name the solutes freely filtered

A

Na+

Cl-

H2O

  • Most is reabsorbed
  • These are NOT normally secreted
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the first mechanism by which water and some solutes can travel from nephron lumen to blood capillaries

A

PARACELLULAR

  • Generally passive and is the movement between cell spaces
  • Driven by conc gradient and/or charge differences
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the 2nd mechanism by which water and some solutes can travel from nephron lumen to blood capillaries

A

TRANSCELLULAR

  • Specific transport protein on the apical membrane (luminal surface of cells lining nephrons)
  • Transport moves the solute into the cell and from there another transporter moves the molecule across the basolateral surface out of the cell from where it is picked up by the blood
  • On the luminal membrane filtered glucose and sodium are co-transported into the cell
  • Glucose is moved out of the cell by facilitated diffusion across basolateral membrane while the sodium is pumped out by the sodium/potassium pump
  • This figure also illustrates that the transport of many solutes including glucose is dependent on the transport of sodium
  • No Na+ movement, no glucose movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is linked to sodium transport

A

Chloride is also moved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens to water when salt is moved from tubular lumen to blood side

A

Water follows by osmosis primarily by a paracellular route

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Process of Na+ reabsorption

A

Active, via a transcellular route and is powered by the basolateral Na+/K+ ATPase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Process of Cl- reabsorption

A
  • Paracellular (passive)
  • transcellular (active)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

General principle of sodium balance

A

Increase [Na+] => increase in ECF vol

Decrease in [Na+] => decrease in ECF vol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do we measure salt levels

A

Indirectly through vol and pressure of ECF

  • If salt level goes up, ECF goes up, BP goes up
  • Increasing P means we have too much salt and should activate mechanisms to excrete salt
  • Conversely decreasing P means we have too little salt and we should activate mechanisms to save/retain salt
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

PNa+

A

Plasma Na+ conc is normally constant due to ADH and thirst mechanisms

(however level can be increased - we still have excess salt in our system)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When managing ECF vol what else do we need to manage

A

Total sodium level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What do kidneys try to match

A

Input to output

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How much salt is ingested per day

A

8-15 g of NaCl/day

150-250 mEq/day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What would happen if we retained salt intake for 1 day

A

Would require retention of 1L of water to maintain tonicity

Leading to an increase in BW of 1 kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is Na+ excreted

A

Kidneys mainly

Skin - sweat

GIT - ver small amts in faeces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What has a potent effect on Na+

A

Diuretic - must watch for hypotension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Renal Na+ handling values

  1. Intake
  2. FIltered
  3. Excreted
A
  1. 150-250 mEq/day
  2. 25000 mEq/day
  3. 150 mEq/day

(excretion < 1% of filtered load)

18
Q

At the PCT, how much of filtered salt is reabsorbed and how

A

PCT - 65% of filtered salt is reabsorbed by BULK FLOW

19
Q

At the thick ascending limb of LOH how much of filtered salt is reabsorbed through specific transporters and how

A

25% of filtered salt is reabsorbed through specific transporters (targets of loop diuretics)

20
Q

Where is the remaining 10% of salt (in renal Na+ handling) managed

What is its reabsorption controlled by

A

in the distal nephron

Reabsorption is controlled by local and systemic actors working at the level of the distal nephron

21
Q

REGIONAL HANDLING OF Na+ Cl- AND H2O

Proximal tubule

A

Iso-osmotic reabsorption

22
Q

REGIONAL HANDLING OF Na+ Cl- AND H2O

Loop of Henle

A

Separation of salt and H2O (salt moves but water is prevented from following)

23
Q

REGIONAL HANDLING OF Na+ Cl- AND H2O

Distal tubule and collecting duct

A

Reabsorption is regulated by hormones

24
Q

Iso-osmotic reabsorption from proximal tubule

Where is the PT

Difference between interstitium of cortex and plasma

A

PT is in the cortex

Interstitium of cortex is iso-osmotic to plasma

sodium plays a key role in the movement of many other molecules

25
Q

How is Na+ balance maintained (GFR)

A

Small changes in GFR are normal and used as a way to increase the flow (reducing time for absorption) or decrease the flow (increase time for absorption) of fluid through the nephron

  • increase GFR => promote excretion of salt
  • decrease GFR => promote retention of salt
26
Q

How is RBF reduced in response to ECF vol changes

A

By sympathetic nerves, catecholamine and Ang II

27
Q

Glomerular Tubular Balance

A

Protective mechanism

Ensures we always reabsorb a min essential amt of salt to maintain fluid volumes and pressures

When GFR changes, the PCT reabsorbs a constant fraction of the filtered load

=> GFR increases, PCT reabsorption increases

(PCT absorbs 65% of filtered salt - GTB maintains this balance even if GFR increases and filtered load increases)

28
Q

Effect of changes in GFR on PCT

A

PCT reabsorbs more than normal - 65% of a FIXED FRACTION

As a result of the increased GFR we deliver 900 mEq more sodium to the LOH each day

29
Q

Effect of changes in GFR on the LOH

A

In the LOH, there is limited spare capacity

We save more than normal (300 mEq more Na+)

But we end up delivering approx 600 mEq more Na+ to the DCT and thus up to 600 mEq more sodium is excreted from the body due to a 10% increase in GFR

Therefore changing GFR is a way to get rid of salt from the body

30
Q

Renin-Angiotensin System

A
  • Multi-step pathway for maintaining ECF vol and BP
  • RENIN converts angiotensinogen -> Ang I
  • ANGIOTENSIN CONVERTING ENZYME (ACE) converts Ang I -> Ang II
  • found in endothelial cells of all BVs
  • Ang II (a potent vasoconstrictor that increases BP to maintain GFR in the face of a P drop) stimulates aldosterone release
31
Q

What does aldosterone do to Na+ reabsorption

A

An increase in aldosterone increases Na+ reabsorption

32
Q

Where does aldosterone come from

A

Adrenal cortex (zona glomerulosa)

33
Q

Target of aldosterone

A

Distal nephron (P cells)

34
Q

What does aldosterone affect

A

The final 5-10% of Na+ remaining in the nephron (filtrate)

35
Q

Aldosterone is secreted in response to

A

Increase in [K+] and decrease in osmolarity at adrenal cortex

Indirectly via Ang II

36
Q

Mechanism of action of Aldosterone

A

Activate gene transcription of sodium channels called ENaCs and promote the insertion of these channels into the luminal membrane

In this way it promotes salt conservation and retention in the body

37
Q

Major mechanisms for promoting renin release

A

All link back to a salt deficit and the need to promote salt retention

38
Q

What is responsible for promoting salt loss

A

Natiuretic hormones

39
Q

ANP - Atrial Natiuretic Peptide

  1. Plasma level
  2. Where is it stored
  3. How is it released
  4. MOA
A
  1. 3-5 pM
  2. Stored in granules in the myocytes of atria
  3. If we have too high a salt load, the ECF vol increases and the vol of blood returning to the heart increases - super-distension of the atrial walls in response to this cuases the release of ANP
  4. Works by promoting a slight increase in GFR - receptors in the brain via neural arcs appear to inhibit renin release - net effect is to promote Na+ excretion
40
Q

Hypovolemia

A
41
Q

Hypervolemia

A

Renal Physiology (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions