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2A - Urinary System > ECF Volume Regulation 2 > Flashcards

ECF Volume Regulation 2 Flashcards

1
Q

How is ECF volume regulated?

A

By regulation of Na

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2
Q

What hormone promotes Na reabsorption?

A

aldosterone

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3
Q

What does ANP stand for?

A

Atrial natriuretic peptide

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4
Q

What hormone promotes Na excretion?

A

ANP

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5
Q

What effect does aldosterone have on Na and K?

A

Sodium retention and potassium loss

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6
Q

What is diuresis?

A

Increased production of urine

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7
Q

What are the effects of aldosterone?

A
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8
Q

Which of ANP and aldosterone override the other?

A

ANP overrides aldosterone effects on Na reabsorption because of volume expansion

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9
Q

What is Conn’s syndrome?

A

Primary hyperaldosteronism

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10
Q

What is the medical term for increased serum Na?

A

Hypernatraemic

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11
Q

How does Conn’s syndrome impact K and Na?

A

K is depleted

Na is unaffected

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12
Q

What is ANP secreted by?

A

Atrial cells

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13
Q

What is ANP secreted in response to?

A

Expansion of ECF volume

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14
Q

What does ANP cause?

A
  • Natriuresis, loss of Na and water in urine
  • Action may to inhibit secretion of renin, generally opposes actions of angiotensin II
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15
Q

What effect does ANP have on the hypothalamus?

A

Decreased vasopressin secretion

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16
Q

What effect does ANP have on the kidneys?

A

Increased GFR

Decreased renin secretion

17
Q

What effect does ANP have on the adrenal cortex?

A

Less aldosterone production

18
Q

What effect does ANP have on the medullar obongata?

A

Decreased blood pressure

19
Q

What is osmotic diuresis?

A

Increase in urination rate caused by presence of certain substances in the small tubes of the kidneys, occurring when substances such as glucose enter the kidney tubules and cannot be reabsorbed due to pathology

20
Q

Osmotic diuresis is important clinically in explaining what?

A
  • Important clinically in explaining effect of uncontrolled diabetes in producing hyperglycaemic coma
21
Q

Explain what happens in uncontrolled diabetes where [BG] is not controlled so the high plasma glucose exceeds maximum resorptive capacity in the proximal tubule?

A

1) Glucose remains in tubule and exerts osmotic effect to retain water in tubule
2) Therfore [Na] in lumen is decreased because Na is present in larger volume
3) Since Na gains access to proximal tubule cells by pasive diffusion down concentration gradients created by active transports out basolateral surface, Na reabsorption will be decreased, also decreasing ability to reabsorb glucose since it shares symport with Na
4) In descending limb of loop of Henle, movement of water into interstitial from tubule is reduced because glucose and excess Na exert an osmotic effect to retain water, therefore fluid is descending limb is not so concentrated
5) Meaning fluid delivered to ascending limb is less concentrated
6) Since NaCl pumps in ascending limb are gradient limited, medullary interstitial gradient is much less and therefore large reduction of NaCl and water reabsorbed from loop of Henle
7) So large volume of water and NaCl delivered to distal tubule and interstitial gradient is gradually abolished
8) Under normal circumstances, large volume of NaCl and water delivered to distal tubule means there is excess ECF volume and therefore need to get rid of NaCl and water
9) Macula densa will detect high rate of delivery of NaCl so that renin secretion will be suppressed and therefore Na rebsorption at distal tubule will be decreased
10) So uncontrolled diabetes leads to large volume of nearly isotonic urine being excreted causing decrease in plasma volume

22
Q

What does the 200mOsm gradient at each horizontal level of ascending limb reflect?

A

Pumping of the active pumps

23
Q

What is the different in gradient between ascending limb and interstitial fluid at each horizontal level?

A

200mOsm

24
Q
A
25
Q

In uncontrolled diabetes, why is [Na] in the lumen of the tubules decreased?

A

Glucose remains in tubule and exerts an osmotic effect to retain water in tubule

26
Q

What is the consequence of [Na] in the tubule lumen being decreased in uncontrolled diabetes?

A

Since Na gains access to proximal tubule cells by passive diffusion down concentration gradient created by active transport out of basolateral surfaces, Na reabsorption will be decreased, also decreasing the ability to reabsorb glucose since it shares symport with Na

27
Q

In uncontrolled diabetes, why is movement of water into interstitial from tubule reduced?

A

Because glucose and excess Na exert an osmotic effect to retain water, therefore fluid in descending lumb is not so concentrated

28
Q

What is the consequence of movement of water into interstitial from tubule being reduced in uncontrolled diabetes?

A

1) Fluid in descending limb is less concentrated
2) Fluid delivered to ascending limb is less concentrated
3) Since NaCl pumps in ascending limb are gradient limited, medullary intersitial gradient is much less, therefore large reduction in volume of NaCl and water reabsorbed from loop of Henle
4) So large volume of NaCl and water delivered to distal tubule and interstitial gradient gradually abolished

29
Q

In uncontrolled diabetes, why is reabsorption of Na at the distal tubule reduced?

A

Macula densa will detect high rate of delivery of NaCl so that renin secretion will be suppressed and therefore Na reabsorption at distal tubule will be decreased

30
Q

What is caused due to the impact of uncontrolled diabetes on absorption of NaCl and water in the kidneys?

A

Large volume os nearly isotonic urine being excreted causing decrease in plasma volume (PV)

31
Q

What is the tonicity of urine in uncontrolled diabetes (hypotonic, isotonic, hyperotnic)?

A

Nearly isotonic

32
Q

What does the decrease in plasma volume (PV) due to uncontrolled diabetes stimulate?

A

ADH release via baroreceptors but cannot be effective because interstitial gradient has run down

33
Q

What does PV stand for?

A

Plasma volume

34
Q

How much urine a day can patients with uncontrolled diabetes produce, and what can this lead to?

A
  • These patients can produce up to 6-8L of urine/day, causing severe salt and water depletion
35
Q

What can the massive urine production in uncontrolled diabetes lead to?

A

Decreased in plasma volume -> Hypotension -> Hyperglycaemic coma -> Death

36
Q

What is the coma due to hyperglycaemia caused by?

A

Decreased blood flow to the brain

37
Q

What is the coma due to hypoglycaemia caused by?

A

Inadequate glucose for the brain

38
Q

What ions are also involved in the transport mechanism on thick ascending loops of Henle for NaCl?

A

K ions (ie Na+-K+-2Cl- co-transporter)

39
Q

Is the transport (by Na+-K+-2Cl- co-transporter) of NaCl and K in the ascending loops of Henle passive or active?

A
  • This is a passive process, energy is provided by active transport Na+/K+ATPase on basolateral membrane)

2A - Urinary System (30 decks)

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