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I've got kidney disease > Lecture 22 > Flashcards

Lecture 22 Flashcards

1
Q

What causes rickets?

A

due to a deficiency or impaired metabolism of vitamin D, calcium or phosphorus. The predominant cause is vitamin D deficiency

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2
Q

What activates vitamin D3?

A

the kidneys

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3
Q

The Ca2+ you can deal with depends on what?

A

your diet

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4
Q

Ca2+ homeostasis is a balance between that three things?

A
  • kidneys
  • intestine
  • bone
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5
Q

Daily Ca+ intake equals what? What does this mean for the net?

A

daily Ca2+ excreted

net = 0

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6
Q

How much Ca2+ do we typically take in from our diet?

A

1000 mg

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7
Q

How much Ca2+ do we excrete in our faeces

A

800 mg

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8
Q

How much Ca2+ do we excrete in our urine?

A

200 mg

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9
Q

If our Ca2+ is too low, where so we get it from?

A

we break down bone to get it

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10
Q

Where is most of the Ca2+ in our body stored? What percentage does this make up?

A

bone and teeth

99%

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11
Q

What is the concentration of Ca2+ in the ICF? What percent does this make up?

A

generally < 0.1 μM (1%)

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12
Q

What is the concentration of Ca2+ in the ECF? What percent does this make up?

A

2-3 mM (0.1%)

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13
Q

What is the concentration of Ca2+ in the ECF that results in hypercalcemia?

A

ECF > 3 mM = hypercalcemia

High Ca2+ blood

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14
Q

What is the concentration of Ca2+ in the ECF that results in hypocalcemia?

A

< 2 mM = hypocalcemia (Low Ca2+ blood)

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15
Q 
Why is it important to maintain appropriate ICF and ECF concentrations of Ca2+?
• proper \_\_\_\_\_\_\_\_ formation
• \_\_\_\_\_\_\_\_\_\_\_
• \_\_\_\_\_\_\_, cell \_\_\_\_\_\_ and \_\_\_\_\_\_\_\_ 
• muscle \_\_\_\_\_\_\_\_
• blood \_\_\_\_\_\_\_
• \_\_\_\_\_\_\_\_
• \_\_\_\_\_\_\_\_\_ reactions
• \_\_\_\_\_\_\_\_ messenger function
A
  • proper bone formation
  • neurotransmission
  • mitosis, cell division and growth
  • muscle contraction
  • blood clotting
  • growth
  • enzymatic reactions
  • 2nd messenger function
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16
Q 
What are 6 problems with low ECF Ca2+?
• increase \_\_\_\_\_\_\_\_ of: 
– \_\_\_\_\_\_\_\_ cells
– \_\_\_\_\_\_\_ cells
• '\_\_\_\_\_\_ and \_\_\_\_\_\_\_'
• \_\_\_\_\_\_\_ obstruction
• \_\_\_\_\_\_ seizures
• cardiac \_\_\_\_\_\_\_\_
• hypocalcemia \_\_\_\_\_\_\_
– muscle \_\_\_\_\_\_\_
A 
• increase excitability of: 
– nerve cells
– muscle cells
• 'pins and needles'
• airway obstruction
• epileptic seizures
• cardiac arrhythmias
• hypocalcemia tetany
– muscle spasms
17
Q 
What are problems with high ECF Ca2+?
- decrease \_\_\_\_\_\_ of: 
– \_\_\_\_\_ cells
– \_\_\_\_\_\_ cells
- disorientation \_\_\_\_\_\_
- cardiac \_\_\_\_\_\_
- \_\_\_\_\_\_
A 
- decrease excitability of: 
– nerve cells
– muscle cells
- disorientation lethargy
- cardiac arrhythmias
- death
18
Q

Which of the following statements is TRUE?
A. The bulk of Ca 2+ in the body is located within the
ICF.
B. Low ECF Ca2+ causes decreased excitability of nerve cells.
C. The ECF Ca2+ concentration is between 2-3 mM.
D. Osteoporosis causes and increase in bone mass.

A

C. The ECF Ca2+ concentration is between 2-3 mM.

19
Q

In what three forms is Ca2+ held in the plasma? What percentages do each of these forms make up?

A

• 50% of the Ca2+ is ionized
• 40% of the Ca2+ is bound to protein (normally albumin), thus not filtered
• 10% of the Ca2+ is complexed with anions (HCO-3, citrate, phosphate,
SO4=)

20
Q

How much of the Ca2+ in the plasma can be filtered?

A

60%

21
Q

Calculate the daily filtered load of Ca2+ given that the [Ca2+]plasma is 2.5 mmol/L

A

180 L/day x 2.5 mmol/L = 450 mmoles/day (filtered)

22
Q

Which parts of the nephron reabsorb Ca2+ and what percentage of the Ca2+ load do each of there make up?

A 
PT: 50-60%
thick ascending loop: 15%
DT: 10-15%
CCD: 1%
1% is excreted
23
Q

How is Ca2+ reabsorbed in the proximal tubule?

A

This is purely through the paracellular pathway (solvent drag) due to the PT having leaky absorptive epithelium. The lumen is + charged as so Ca2+ leaves

24
Q

What is solvent drag?

A

refers to solutes in the ultrafiltrate that are transported back from the renal tubule by the flow of water rather than specifically by ion pumps or other membrane transport proteins

25
Q

How is Ca2+ reabsorbed in the thick ascending loop of Henle?

A

This is leaky absorptive epithelium. There is a NKCC2 in the apical membrane and a Ca2+ receptor in the basolateral membrane which monitors Ca2+ conc in the ECF.
If hypercalcaemic, the Ca2+ sensing receptor will respond by altering the function of both the NKCC2 and the K+ channel to reduce the Ca2+ that is coming into the cell
If hypocalcaemic conditions, the the Ca2+ sensor notes this and doesn’t alter the function of NKCC2 and K+ channel so Ca2+ still comes in. Also Ca2+ moves through paracelluarly allowed by claudin 16

26
Q

How is Ca2+ reabsorbed in the distal convoluted tubule?

A

This is tight absorptive epithelium and reabsorption occurs through the TRPV5 and TRVP6 channels in the apical membrane down its conc gradient. It then binds to calbindin which shuttles Ca2+ across the epithelial cell to the basolateral membrane and it exits through Ca2+ ATPase (PMCa1b) and NCX1 which is a Ca2+/Na+ exchanger

27
Q

Which of the following statements is FALSE?

A. 50% of the Ca2+ in plasma is ionized.
B. 60% of the blood Ca2+ can be filtered at the glomerulus.
C. The proximal tubule reabsorbs 50-60% of the filtered Ca2+.
D. Ca2+-sensing receptors monitor the intracelular Ca2+ concentration.

A

D. Ca2+-sensing receptors monitor the intracelular Ca2+ concentration.

28
Q

What are two hormones involved in Ca2+ homeostasis?

A

parathyroid hormone

calcitriol

29
Q

Where is the parathyroid hormone secreted from?

A

Chief cells in the parathyroid gland have a Ca2+ sensor on the membrane of them which monitor ECF Ca2+ levels

30
Q

Where is calcitriol secreted from?

A

This is a metabolite of vitamin D3 - activated in the proximal tubule of the kidney

31
Q

What is parathyroid hormone secreted in response to?

A

Low Ca2+ plasma levels (hypocalcemia)

32
Q

What is the effect of parathyroid hormone?

A

This stimulates bone breakdown (resorption) which releases Ca2+ into the plasma.
It also stimulates resorption of Ca2+ by the TAL and DT
It also increases the release of calcitriol which results in increased Ca2+ absorption by the intestine

33
Q

What are the effects of calcitriol?

A
  • Calcitriol is released by the influence of PTH due to low calcium
  • stimulates resorption (breakdown) of bone and releases Ca2+ into the plasma
  • stimulates reabsorption of Ca2+ by the DT
  • stimulates Ca2+ absorption by the intestine
  • negative feedback on the parathyroid gland to regulate the release of PTH
34
Q

Which of the following statements is FALSE?

A. The kidneys, bone and intestine all play roles in Ca2+
homeostasis.
B. The parathyroid hormone is released by high plasma Ca2+.
C. Calcitriol is activated vitamin D3.
D. Parathyroid hormone stimulates resorption of bone.

A

B. The parathyroid hormone is released by high plasma Ca2+.

I've got kidney disease (43 decks)

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