Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Physiology > Ca and bone physiology > Flashcards

Ca and bone physiology Flashcards

1
Q

What is the normal plasma [Ca]?

A

9-10.5 mg/dL

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

What three forms does Ca take in the body?

A

Free/ionized
Protein bound
Anion bound

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

What is the relationship between plasma pH and bound Ca levels?

A

Lower pH = less Ca bound to protein

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

Significant decrease in plasma calcium can lead to death because of what effect?

A

because of the effect of calcium on nerve excitability

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

As extracellular calcium concentration gets lower, sodium channels open (more/less) readily?

A

More

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

What happens to the membrane potential of neurons with hypocalcemia?

A

Makes it closer to membrane potential, making the neuron more excitable

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

Does hypocalcemia cause tetany or flaccid paralysis?

A

tetany

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

What is Trousseau sign?

A

Contraction of the hand when a BP cuff is applied. This is caused by hypocalcemia

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

What is Chvostek sign?

A

When the facial nerve is tapped at the angle of the jaw, the facial muscles on the same side of the face will contract momentarily (typically a twitch of the nose or lips) because of hypocalcemia

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

What is the effect of hypocalcemia on the heart?

A

CHF

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

When the concentration of calcium is higher than normal the voltage-regulated sodium channels are (more or less) likely to open at any given cell membrane potential?

A

Less

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

What is the effect of low [Ca] on membrane potential?

A

Lowers threshold, leading to hyperexcitability

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

• Some calcium enters the GI tract from the body e.g. sloughing of cells that line GI tract, in various secretions into GI tract. Why is this not problematic?

A

This loss of calcium relatively fixed and less than calcium uptake

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

What is the effect of increased Vitamin D on calcium uptake?

A

Increases uptake

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

The higher the plasma [Ca] levels, the higher or lower the threshold?

A

higher

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

How tightly regulated is plasma phosphate concentration relative to [Ca]?

A

Much less

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

What is the normal range for plasma [phosphate]?

A

3-4.5 mg/dL

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

What is the main circulating form of phosphate? How filterable is this?

A

Free, inorganic ion–very filterable

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

Where is phosphate stored? What form is this in?

A

Bone

Stored as hydroxyapatite

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

What is the role that vitamin D plays in phosphate uptake from the diet?

A

Increases, but only marginally

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

What is the role of PTH on phosphate secretion?

A

greatly increase phosphate excretion by the kidneys.

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

What is the primary regulator of phosphate?

A

FGF23

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

What is the effect of FGF23 on the production of calcitriol?

A

Decreases

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

What is the specialized channel on the intestinal epithelium that moves Ca into the epithelial cells?

A

TRPV5/6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is the protein in the intestinal epithelial cells that binds to Ca and moves it across the lumen?
Calbindin
26
What is the transporter that moves Ca from the intracellular fluid of the intestinal cytoplasm to the plasma?
Plasma membrane Ca ATPase
27
What is the most important bone salt?
hydroxyapatite
28
Why does hydroxyapatite precipitate in bone and not in other tissues?
There are inhibitors found in other body tissues including plasma to prevent precipitation.
29
What are the two effects of PTH has in the Ca pathway?
Increases calcitriol synthesis Increases phosphate excretion
30
What are the two effects of FGF23 has in the Ca pathway?
Decreases calcitriol synthesis Increases phosphate excretion
31
Why is it important that PTH and calcitriol have opposite effects on calcitriol synthesis, but both contribute to phosphate excretion?
Can increase phosphate excretion without changing calcitriol synthesis
32
What is the major protein found in bone?
Collagen I
33
What is the chemical that stimulates osteoblasts?
Growth hormone
34
What is osteoid formation?
When osteoblasts entrap themselves in bone, becoming osteocytes
35
The growth of long bones at epiphyseal cartilages is under the control of what hormone?
GH
36
What is the effect PTH has on osteoclast activity? How?
Increases activity by binding to receptors on osteoblasts, which release osteoprotegerin ligand (OPGL).
37
What is osteoprotegerin ligand (OPGL)?
A hormone released by osteoclasts that activates receptors on preosteoclast cells to stimulate their growth
38
What is osteoprotegerin (OPG)?
Hormone released by osteoblasts that **inhibits** the binding of OPGL on pre-osteoclasts, preventing their maturation.
39
What is the hormone that stimulates osteoprotegerin (OPG) production?
Estrogen
40
What is the hormone that decreases osteoprotegerin (OPG) production?
PTH and glucocorticoids
41
What happens to osteoclasts/blast activity when a bone is fractured?
Large increase in osteoprogenitor cells
42
What temporarily holds fractured bones in place?
A callus
43
What are the nutritional cells of bone?
Astrocytes
44
What are the canals in bone that allows for the transport of nutrients?
Haversian canals
45
What are the passages that connect Haversian canals in bone?
Canaliculi
46
What is an osteon?
Haversian canal and surrounding canaliculi
47
What prevents the osteoclasts enzymes from spreading outside the site of degradation?
Tight connections--integrins
48
What are the two hormones that act on osteoblasts to stimulate OPGL production (thus stimulating Pre-osteoclast maturation)?
PTH and Vit D
49
What is the active form of Vitamin D?
1,25-Dihydroxycholecalciferol
50
What is the hormone required to have the proximal tubules in the kidney convert 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol?
PTH
51
What is the enzymes that converts Vitamin D3 into 25-hydroxycholecalciferol?
25-Hydroxylase
52
What is the enzyme that converts 25 hydroxycholecalciferol to 1,25- dihydroxycholecalciferol?
1alpha-Hydroxylase
53
What is the effect of 1,25-dihydroxycholecalciferol ?
Increases both calcium and phosphate concentrations in plasma via increased reabsorption
54
What is the effect of 1,25-dihydroxycholecalciferol on bones?
promotes action of PTH on osteoclasts increasing bone resorption
55
What causes Rickets in children?
caused by a calcium or phosphate deficiency in the extracellular fluid usually caused by a lack of vitamin D. Children are more susceptible since childhood is a period of bone growth so large amounts of calcium are needed.
56
What is Osteomalacia?
(softening of the bone due to deficient mineralization) can be caused by a type of “Renal rickets” due to the failure of the damaged kidney to produce the active form of vitamin D.
57
What is the substrate that changes to previtamin D3 in the presence of sunlight?
7-Dehydrocholesterol
58
What is the primary physiological stimulus for PTH secretion?
Decreased [Ca]
59
How does the absence of PTH cause death?
From hypocalcemic tetany
60
What is the effect of PTH on plasma [Ca] and [phosphate]?
Increases [Ca] | Decreases [phosphate]
61
Why is it important that PTH decreases plasma [phosphate] with increasing [Ca]?
Prevents crystallization of calcium phosphate.
62
Where in the nephron does PTH regulate the reuptake of Ca?
distal portions of the nephron
63
What is the effect PTH has on the reabsorption of phosphate at the kidney?
Inhibits reabsorption
64
What is hormone that increases 1alpha-hydroxylase activity? What does this do?
PTH--increases Vitamin D synthesis, thus increases Ca reabsorption in the intestines
65
What are the three effects that PTH has on bone?
* Increases bone resorption and delivery of calcium to plasma * Inhibits collagen synthesis by osteoblasts * Active form of vitamin D increases PTH driven bone resorption
66
Where is calcitonin produced?
parafollicular cells in the thyroid gland
67
What type of hormone is calcitonin?
Polypeptide
68
What stimulates calcitonin release?
Increase in plasma Ca
69
How significant of a role does calcitonin play in Ca homeostasis?
Not very
70
What is the effect of calcitonin on bones?
Decreases bone resorption and thus decreases calcium release
71
What is the effect of calcitonin on the kidney?
decrease in reabsorption of calcium and phosphate
72
What is the feedback mechanism for PTH?
PTH causes increase in vit D, thus increasing Ca reabsorption via CBP + Ca stimulated ATPase in the intestine. Resulting increase in plasma [Ca] inhibits PTH
73
Where are the parathyroid glands? How many are there?
next to the thyroid, there are four
74
What is the relationship between plasma [Ca] and [PTH]?
Inverse--sigmoidal curve
75
How does PTH increase Ca reabsorption?
Increases Vit D synthesis via activation of 1alpha-hydroxylase
76
What are the effect of hyperparathyroidism?
Hypercalcemia and hypophosphatemia
77
What are the symptoms of hyperparathyroidism?
Renal stones Weak bones Constipation
78
What causes secondary hyperparathyroidism?
Anything that causes low Ca levels (kidney disease)
79
Why is it lethal to not have PTH?
steady decline in the plasma concentration of calcium
80
Renal function may increase plasma [PO3], causing hyperphosphatemia. What are the two main hormones that this lead to an increase in production of?
PTH | FGF23
81
What is the effect of FGF23 on vit D synthesis? How? What is the effect of this on [PTH]?
Decreases vit D by inhibiting 1alpha hydroxylase Stimulates PTH synthesis
82
What is the effect of PTH on bone?
Increases bone reabsorption, and release of Ca + PO3
83
What are the two supplements and one dietary restriction that patients with CKD should be prescribed?
Supplement Ca, and Vit D Restrict PO3

Physiology (75 decks)

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