Brainscape's Knowledge GenomeTM

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


See full index

BRS > Regulation of calcium and phosphate > Flashcards

Regulation of calcium and phosphate Flashcards

1
Q

Where is most of the calcium stored?

A

Skeleton.

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

What is the active form of calcium?

A

Unbound ionised calcium.

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

What is calcium usually bound to?

A

Plasma proteins and anions such as phosphate.

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

What hormones increase calcium levels in the blood?

A

Parathyroid hormone and calcitriol (active vitamin D3).

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

What secrets parathyroid hormone?

A

Parathyroid glands.

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

Where can you get vitamin D from?

A

Diet and sunlight.

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

Where does parathyroid hormone and calcitriol target to alter calcium levels?

A

Kidney, bone and gut.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What hormones decrease calcium levels in the blood?

A

Calcitonin.

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

What secretes calcitonin?

A

Parafollicular cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How essential is calcitonin?

A

Not essential. Calcium can be regulated without calcitonin production.

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

What are the sources of vitamin D2?

A

Plants.

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

What is another name for vitamin D2?

A

Ergocalciferol.

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

What are sources of vitamin D3?

A

UV radiation of skin and animal foods.

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

What is anotehr name for vitamin D3?

A

Cholecalciferol.

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

Vitamin D metabolism steps in the skin?

A

7-dehydrocholesterol is converted to pre-vitamin D3. Pre-vitamin D3 is then converted to vitamin D3. Vitamin D3 is secreted into blood.

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

Vitamin D metabolism to form calcitriol?

A

Vitamin D3 (or Vitamin D2) is hydroxylated by the enzyme 25-hydroxylase in the liver to produce 25 (OH) Vitamin D3. 25(OH) Vitamin D3 is hydroxylated by 1 alpha-hydroxylase in the kidney to produce 1,25(OH)2 Vitamin D3 also known as calcitriol.

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

How does calcitriol result in negative feedback?

A

Increased calcitriol reduces transcription of 1 alpha-hydroxylase resulting in less calcitriol being produced. Calcitriol production also inhibits PTH secretion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why is 25-hydroxyvitamin d3 useful?

A

Much easier to measure than calcitriol (1,25 dihydroxyvitamin d3) and so can be used as a reference point for levels of calcitriol.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the main way in which calcitriol increases calcium levels?

A

Increases calcium and phosphate absorption from the gut.

20
Q

What are the other ways in which calcitriol increase calcium?

A

Increases calcium reabsorption from the bone and increases calcium and phosphate reabsorption from the kidney.

21
Q

What specific cells secrete parathyroid hormone?

A

Chief cells in parathyroid glands.

22
Q

How is parathyroid hormone made?

A

Cleavage of Prepro - PTH.

23
Q

How is PTH secretion regulated in the parathyroid glands?

A

Calcium from the blood binds to the G-protein coupled calcium sensing receptor. If more calcium binds to the receptors then less PTH is released. Vice versa. PTH secretion is inversely proportional to calcium serum levels.

24
Q

What does PTH target and how does it affect calcium and phosphate levels?

A

PTH increases calcium reabsorption from bone. PTH increases calcium reabsorption from kidney and increases excretion of phosphate from kidney. PTH also increases 1-alpha-hydroxylase activity in the kidney resulting in greater calcitriol synthesis. This leads to greater calcium and phosphate absorption from the gut.

25
Q

What is the mechanism of PTH on bone?

A

PTH binds to PTH receptor on osteoblasts. Results in release of osteoclast activating factors which turn the osteoblast into an osteoclast. Osteoclasts result in greater calcium reabsorption; greater calcium levels in blood.

26
Q

What is the mechanism of calcitriol on bone?

A

Calcitriol has different effects depending on serum calcium levels. If there is low serum calcium then calcitriol increases calcium by increasing formation of osteoclasts. If there is normal serum calcium then calcitriol promotes bone formation by increasing formation of osteoblasts.

27
Q

What inhibits PTH secretion?

A

Calcitriol synthesis and increased calcium.

28
Q

What promotes PTH secretion?

A

Low blood calcium.

29
Q

How does calcitonin lower calcium levels if calcium levels are too high?

A

Reduce osteoclast activity in bone and increase calcium excretion in kidney.

30
Q

What protein regulates phosphate levels?

A

FGF23.

31
Q

Where is FGF23 produced?

A

In the bone.

32
Q

How does FGF23 regulate phosphate levels?

A

Blocks sodium phosphate co-transporter in kidney. Reduces reabsorption of phosphate in kidney. FGF23 inhibits calcitriol synthesis in kidney and so results in less phosphate absorption in gut.

33
Q

How does PTH increase excretion of phosphate in the kidney?

A

Blocks sodium phosphate co-transporter in kidney. Reduces reabsorption of phosphate in kidney.

34
Q

What does high calcium do to neurones?

A

Results in less membrane excitability as high calcium levels block sodium influx.

35
Q

What does low calcium do to neurones?

A

Results in more membrane excitability as it enables greater sodium influx.

36
Q

Hypocalcemia symptoms?

A

CATs go numb (convulsions, arrythmias, tetany, paraesthesia).

37
Q

How do you test for hypocalcemia?

A

Tap the facial nerve.

38
Q

Hypocalcemia causes?

A

Hypoparathyroidism due to autoimmunity or surgery, vitamin D deficiency. Liver or renal failure.

39
Q

Vitamin D deficiency causes?

A

Malabsorption, inadequate sun exposure, liver disease and renal disease.

40
Q

What does vitamin D deficiency cause?

A

Rickets and osteomalacia - soft bones.

41
Q

Hypercalcemia symptoms

A

Kindey stones (Stones), constipation and nausea (abdominal moans), fatigue and depression (psychic groans).

42
Q

Hypercalcemia causes?

A

Primary hyperparathyroidism, bone metastases.

43
Q

How does primary hyperparathyroidism result in high calcium levels?

A

Too much PTH secretion and no negative feedback.

44
Q

What usually causes primary hyperparathyroidism?

A

Parathyroid gland adenoma.

45
Q

How do bone metastases result in high calcium levels?

A

Activation of osteoclasts results in increased calcium reabsorption.

46
Q

Why is 1-alpha hydroxylase an important enzyme?

A

Drives rate limiting step of calcitriol synthesis.

BRS (52 decks)

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