Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

function of CNS and endocrine > 26 Hormonal regulation of calcium and phosphate balance > Flashcards

26 Hormonal regulation of calcium and phosphate balance Flashcards

1
Q

what processes is calcium essential for

A
  • excitation-contraction coupling
  • stimulus-secretion coupling
  • blood coagulation
  • structural component of bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

where is most of the calcium in the body stored

A

in the bone

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

is phosphate essential for different phsyiology processes

A

yes its a required component of cellular structures and chemicals eg phospholipids

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

mechanisms regulating calcium and phosphate levels

A
  • absorption
  • deposition
  • reabsorption
  • excretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what hormones regulate calcium and phosphate

A
  • parathyroid hormone (PTH)
  • 1,25-dihydroxyvitamin D
  • calcitonin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

is parathyroid hormone a peptide hormone

A

yes

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

what secretes parathyroid hormone and in reponse to what

A

chief cells in response to low plasma calcium levels

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

regulation of PTH secretion

A
  1. calcium binds to CasR (calcium sensing receptor)
  2. causes activation of a signalling pathway and generation of arachidonic acid (AA)
  3. AA inhibits secretion of PTH
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what switches off the signalling pathway to allow PTH secretion

A

reduced calcium levels switch off the signalling pathway to allow PTH secretion

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

is PTHR1(parathyroid hormone receptor 1) a GPCR

A

yes

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

what are the two main targets of PTH

A

bone and kidney cells

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

effects of PTH on calcium and phosphate in BONE

A

stimulates calcium and phosphate reabsorption by (indirectly) stimulating osteoclast activity

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

effects of PTH on calcium and phosphate on KIDNEY

A

enhances reabsorption calcium but decreases reabsorption of phosphate

ie increases phosphate excretion

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

effects of PTH on calcium and phosphate on INCREASED ABSORPTION

A

this effect in indirect and via synthesis of 1,25-dihydroxyvitamin D

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

what is bone

A

connective tissue containing several cell types surrounded by a protein matrix (osteoid)

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

what does a bone mainly contain

A

collagen

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

what is the organic matrix in the bone mineralised by

A

hydroxyapatite, a calcium-phosphate-hydroxide salt

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

is bone highly dynamic

A

yes

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

what are the key cells in regulating bone resorption and formation

A

osteoclasts and osteoblasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what do osteoblasts do

A

mediate bone formation

secrete collagen and other proteins such as osteocalcin and osteopontin (collectively called osteoid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is the process of new bone matrix formation called

A

mineralisation, calcium and phosphate are associated with it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

can osteoblasts become osteocytes

A

yes if they are embedded in the bone matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

can osteoblasts be removed

A

yes by apoptosis or they can become inactive bone-lining cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what do osteoclasts do

A

mediate bone resorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what do osteoclasts secrete

A

proteases and H+ ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what do H+ ions do in the bone

A

dissolve the hydroxyapatite crystals and expose the organic matrix, allowing degeneration of collagen by proteases

results in release of calcium and phosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

does PTH act directly on osteoclasts

A

no, as osteoclasts lack a PTH receptor protein

instead it binds to osteoblasts which leads to osteoclastogenesis from osteoclast precursor cell

28
Q

how does PTH achieve osteoclastgenesis

A

by enhancing expression of RANK ligand (RANKL) and inhibiting expression of osteoprotegerin, a decoy receptor for RANKL

29
Q

what does interaction of RANK with RANKL mediate

A

interaction of osteoblasts with osteoclast precursors

30
Q

what blocks RANK-RANKL interaction

A

osteoprotegerin which binds to RANKL

31
Q

does PTH stimulate the production of new osteoclasts

32
Q

steps of PTH stimulating production of new osteoclasts

A
  1. PTH binds to osteoblast cells, causes increase in RANKL and decrease in osteoprotegerin
  2. this enhances interaction of osteoblasts with osteoclast precursor cells
  3. this leads to activation of signalling pathways that promote differentiation of the precursor cells into mature osteoclasts (which mediate bone resorption)
33
Q

what does a decrease in osteoprotegerin lead to

A

more free RANK ligand which can now bind to rank as an osteoblast precursor

34
Q

does PTH cause reabsorption of calcium in the kidneys

A

yes, reabsorption increases due to PTH stimulation of calcium transporter expression and activity

35
Q

does PTH cause increased reabsorption of phosphate in the kidney

A

yes due to PTH stimulated internalisation and lysosomal degradation of a phosphate transporter

ie removal from the plasma membrane

36
Q

what is enhanced excretion of phosphate important form in kidneys

A

to prevent plasma levels of this ion rising as a result of increased resorption form bone and increased absorption from intestine

37
Q

does PTH increase synthesis of 1,25-dihydroxyvitamin D

A

yes, which increases calcium and phosphate absorption from the intestines

38
Q

is 1,25-dihydroxyvitamin D a steroid hormone

A

yes, it comes from cholesterol

39
Q

does 1,25-dihydroxyvitamin D have a key role in regulating calcium and phosphate

40
Q

how is vitamin D synthesised

A
  • in the body (requires sun exposure; UV light)
  • obtained from ingested food
41
Q

is 1,25-dihydroxyvitamin D the active form of vitamin D

42
Q

does PTH increase synthesis of 1,25-dihydroxyvitamin D

43
Q

how does PTH increase synthesis of 1,25-dihydroxyvitamin D

A

by regulating expression of 25-hydroxyvitamin D 1-alpha-hydroxylase in the kidney

44
Q

where does 1,25-dihydroxyvitamin D have its main effect

A

in the intestine

45
Q

is 1,25-dihydroxyvitamin D a steroid hormone

A

yes, its receptor in inside the cell

46
Q

what does 1,25-dihydroxyvitamin D binding to its receptor cause

A

gene expression changes

47
Q

effect of 1,25-dihydroxyvitamin D on intestine

A
  • increase calcium and phosphate absorption
  • effects are increased by increased expressions of calcium and phosphate transport proteins
48
Q

effects of 1,25-dihydroxyvitamin D on kidneys

A

increases calcium reabsorption by increasing expression of transporter protein

49
Q

what does 1,25-dihydroxyvitamin D protect bone from

A

the action of PTH by increasing calcium uptake from GI and therefore reducing PTH secretion

50
Q

steps of 1,25-dihydroxyvitamin D regulation of calcium absorption

A
  1. it enters cells
  2. activates receptor in the nucleus
  3. increased transcription/expression of calcium transport proteins
  4. leads to increased absorption of calcium
51
Q

overall effects of PTH and 1,25-dihydroxyvitamin D on calcium

A
  • increased renal calcium resorption
  • increased bone resorption
  • increased ECF calcium
  • increased renal hydroxylation of 25-hydroxy-vitamin D
52
Q

good sources of vitamin D

A
  • from April to September we get it from sunlight
  • foods such as oily fish, red meet
  • dietary supplements
53
Q

how much vit D do babies need

A

up to 1 year old need 8.5 to 10mcg a day

54
Q

how much vit D do children and adults need

A

10mcg a day – including pregnant and breastfeeding women

55
Q

should formula fed babies get vitamin D supplements

A

no until they are having less than 500ml of formula per day

56
Q

what does too much vitamin D cause

A

hypercalcaemia which can weaken bones and damage kidneys and heart

57
Q

can you overdose on vit D through exposure to sunlight

58
Q

does calcitonin (CT) lower blood calcium and phosphate levels

59
Q

is calcitonin a peptide hormone

60
Q

what secretes calcitonin

A

C-cells of the thyroid gland

61
Q

what does calcitonin secrete

A

in response to an elevation in plasma calcium levels

62
Q

is the CT receptor a GPCR

63
Q

two main sites of action for CT

A

osteoclasts in bone and kidney cells

64
Q

does calcitonin inhibit resorption and promotes deposition

65
Q

how does calcitonin inhibit resorption and promote deposition

A

it inhibits the activity and differentiation of osteoclasts

thus inhibits resorption and promotes deposition

66
Q

does calcitonin play a large role in normal regulation of calcium and phosphate balance

A

no but may play a role in protecting skeletal integrity when there is a high calcium demand (such as pregnancy or breast feeding)

67
Q

what controls PTH and calcitonin secretion

A

negative feedback

  • increase in plasma Ca = increase in calcitonin = decrease in plasma Ca
  • decrease in plasma Ca = increase in PTH = increase in vit D and plasma Ca

function of CNS and endocrine (29 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions