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Renal Function 4 Flashcards

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1
Q

Importance of Calcium:

A
  1. stabilizes the excitable cell membrane
  2. 2nd messenger for cell signaling
  3. essential​ for blood clotting

** Tight control of ECF calcium is essential

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2
Q

Importance of phosphate:

A
  1. component of many organic molecules
  2. store and release ATP in bonds
  3. protein phosphorylation control many intracellular processes
  4. urinary buffer

**Tight​ control of phosphate not essential

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3
Q

Mineral homeostasis​:

A
  • dietary intake and absorption
  • distribution within body components (redistributed)
  • excretion (primarily​ by kidney
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4
Q

bone, kidney, and intestine are together regulating?

A

inflow, outflow, and redistribution​ of calcium and phosphate between different body compartments

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5
Q

A physiological​ important component​ of Calcium?

A

Ionized calcium - 50% of Ca in blood
- free form is closely regulated

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6
Q

What affects bound calcium?

A

pH affects the ​amount bound to albumin

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7
Q

What influences complex calcium?

A

plasma phosphate

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8
Q

Where does Ca absorption occue​?

A

upper small intestine
-inefficient process (only 20% absorbed)

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9
Q

What is the calcium binding​ protein in intestinal cells regulated by?

A

Vitamin D3

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10
Q

What happens if a lot of phosphate from the diet binds with calcium?

A

It stops it from being absorbed

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11
Q

Intestinal absorption of Ca is influenced​ by ?

A

active vitamin D

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12
Q

What type of tissue is bone?

A

active - because it remodels

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13
Q

osteclast:​

A

resorb bone - release​ Ca and phosphate

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14
Q

osteoblasts:

A

responsible for new bone formation and its mineralization

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15
Q

bone turnover =

A

balance between resorption and formation

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16
Q

In the Kidney in calcium filtered?

A

Yes - both free and complex Ca is filtered

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17
Q

What % of Ca is reabsorbed in prox​imal tubule (passive reabsorption)?

A

70% -

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18
Q

What type of Ca reabsorption happens in the late distal tubule?

A

active reabsorption regulated by PTH

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19
Q

Does tubular secretion of Ca2+ occur?

A

no

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20
Q

When does uptake of phosphate happen in cells and why?

A

after feeding (insulin) - because insulin stimulates phosphate uptake in order to phosphorylate​ glucose

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21
Q

Phosphate is diet is absorbed by?

A

active transport stimulated by Vitamin​ D3

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22
Q

The more Ca in diet , the more MG, the more multivalent leads to

A

less available phosphate for absorption

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23
Q

What happens to phosphate when calcium is released from bone?

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A

phosphate is also released

24
Q

how much phosphate present in plasma is filtered?

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A

around 90% - not much protein binding of phosphate

25
Phosphate is actively reabsorbed by?
proximal tubule ( Co transport with Na+ which​ is regulated by PTH)
26
phosphate overflow process:
1. Phosphate filtered by the ​glomerulus 2. reabsorbed by proximal tubule via co-transport 3. some escapes from reabsorption (overflow) and is excreted
27
What does the rate of phosphate secretion depend on?
1. depends on GFR 2. It is proportional​ to plasma phosphate 3. phosphate transporter salurate
28
Where will you see phosphate present in urine:
in normal circumstances
29
Excess PTH = __ phosphate
less phosphate
30
lack of PTH = __ phosphate
more phosphate
31
Is a major INTERCELLULAR cation?
magnesium
32
Where is the majority of magnesium present?
bone matrix
33
regulation of Mg:
not understood
34
Is a major site of Mg absorption​?
thick ascending​ loop o
35
___ can increase Mg excretion?
Aldosterone
36
hormones involved in calcium balance?
- PTH - Active Vitamin D3 - Calcitonin --> produced by c-cells in thyroid gland
37
hormones involved in phosphate balance?
- FGF-23 - Hormones regulating calcium also affect phosphate
38
PTH secretion is regulated by?
ionized calcium
39
inhibit PTH (negative feedback)
- vitamin D3 - FGF-23 - severe hypomagnesium
40
Effects of PTH:
- stimulates Ca2+ and phosphate from bone - promotes renal reabsorption of Ca2+ from the distal tubule - Promotes renal excretion of phosphate - stimulates synthesis of active Vitamin D3- 1,25 - promotes Mg absorption from loop
41
Whemn PTH is reduced ___ returns calcium to bone?
1,25 D3
42
PTH: Bone
stimulates release pf Ca and phosphate from bone to ECF
43
PTH: Kidney
- promotes phosphate excretion via urine - makes more 1, 25 Vitamin D3 - reabsorb calcium
44
PTH: ECF
- v1, 25 D3 increases absorption of Ca and phosphate from gut
45
Where is Viatmin D3 obtained?
diet or skin
46
25-hydroxylated by?
liver (not regulated)
47
1 alpha hydroxylated by?
kidney (active)
48
enhances 1 alpha hydroxylated ?
PTH
49
inhibits 1 alpha hydroxylated
phosphate and FGF-23 may
50
24-hydroxylated by ?
kidney (inactive)
51
inhibits 24-hydroxylated:
- PTH
52
enhances 24 hydroxylate?
phosphate / FGF-23
53
Calcitronin is secreted by ?
C- cells of the ​thyroid gland
54
FGF-23 produced by?
osteoblasts and osteocytes in repsonse to an ​increase in ECF phosphate
55
FGF-23 inhibits
phosphate entry / lowers phosphate in ECF by: - inhibiting calcitriol formation ( inhibits PO4 entry in the gut - inhibits PTH secretion ( inhibits PO4 release from bone) - inhibits proximal tubular reabsorption of PO4

Renal (5 decks)

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