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Neuroendocrine > Calcium and Phosphate Homeostasis > Flashcards

Calcium and Phosphate Homeostasis Flashcards

1
Q

Where is most of the body’s Calcium found?

A

Bones and teeth

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2
Q

What is the biologically active form of Calcium?

A

Free, ionized

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3
Q

Decreased calcium levels in the plasma

A

Hypocalcemia

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4
Q

Increased calcium levels in the plasma

A

Hypercalcemia

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5
Q

What are some signs of hypocalcemia?

A

Muscle twitching, hyperreflexia, muscle cramps and tingling and numbness

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6
Q

What does hypocalcemia do to the membrane excitability?

A

It increases membrane excitability (spontaneous APs) by reducing the activation threshold of sodium channels

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7
Q

What are 3 things that can change the calcium concentration in the plasma?

A

Changes in plasma protein concentration
Changes in anion concentration
Acid-base abnormalities

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8
Q

If there is an increase in plasma protein, what does that do to the calcium concentration?

A

Increases total Calcium

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9
Q

If there is an increase in an anion (ex. phosphate), what does that do to the calcium concentration?

A

Decreases ionized Calcium

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10
Q

Alters ionized concentration of calcium by changing fraction of calcium bound to albumin

A

Acid-base abnormalities

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11
Q

If less calcium is bound to albumin, what does that do to ionized calcium levels in the plasma?

A

Increases them (acidemia)

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12
Q

If more calcium is bound to albumin, what does that do to ionized calcium levels in the plasma?

A

Decreases them (Alkalemia)

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13
Q

What are the 3 main hormones that control calcium and phosphate homeostasis?

A

PTH, Vitamin D and Calcitonin

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14
Q

In order to maintain calcium balance, what must the kidney do?

A

Excrete the same amount of calcium that the GI tract absorbed

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15
Q

What is the optimal level of calcium in the ECF?

A

10 mg/ml

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16
Q

Phosphate concentration is _____ related to calcium concentrations

A

Inversely

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17
Q

Only 50% of calcium is ionized, what is the percentage of phosphate that is ionized?

A

84%

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18
Q

What cells in the parathyroid synthesize and secrete PTH?

A

Chief cells

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19
Q

If there is LOW calcium plasma levels, what will be secreted MORE?

A

PTH

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20
Q

What inhibits PTH synthesis and secretion?

A

Hypercalcemia

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21
Q

What senses calcium plasma levels?

A

CaSR receptors

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22
Q

If there is low calcium, PTH will increase. What are its main actions?

A

Increase bone resorption
Increase Calcium reabsorption from kidneys
Increase Calcium reabsorption from intestines

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23
Q

What type of hormone is Vitamin D?

A

Steroid hormone

24
Q

What is the action of Vitamin D on calcium and phosphate concentrations?

25
How does Vitamin D promote bone mineralization?
Increases CaXPi
26
What activates 1alpha-hydroxylase to form the active version of Vitamin D?
Low calcium and low phosphate | High PTH
27
Where is Vitamin D synthesis?
Kidney tubule
28
What activates CYP1alpha gene?
Increased PTH
29
What suppresses the CYP1alpha gene using what mechanism?
Increased calcium suppresses it using CaSR
30
The CYP1alpha gene codes for what?
1alpha-hydroxylase which activates Vitamin D
31
Short term, what does PTH do to bone?
Bone formation
32
Long term, what does PTH do to bone?
Bone resorption (degradation)
33
What helps PTH synergistically stimulate osteoclast activity for bone resorption?
Vitamin D
34
HOW does PTH increase bone resorption?
Increases RANKL release from osteoblasts and decreases OPG
35
HOW does Vitamin D increase bone resorption?
Increases RANKL
36
Osteoblasts release RankL, how does that result in bone resorption?
It binds RANK receptors on osteoclasts and activates them
37
Where are PTH receptors located for bone remodeling?
On osteoBlasts
38
What activates the thyroid gland to release calcitonin?
Increased Calcium levels
39
What does Calcitonin do?
Stimulates bone formation and decreases the reuptake of calcium in the kidney
40
For bone formation, where are calcitonin receptors?
On osteoClasts to reduce their activity
41
Increased PTH which results in increased Ca | - stones, bones and groans
Primary hyperparathyroidism
42
Primary hyperparathyroidism
Increased PTH, Ca, Vitamin D | Decreased Pi
43
Decreased Ca which causes an increased PTH
Secondary hyperparathyroidism
44
Secondary hyperparathyroidism
Increased PTH | Decreased Ca, Vitamin D
45
Decreased PTH which causes decreased calcium
Hypoparathyroidism
46
Hypoparathyroidism
Decreased PTH, Ca, Vitamin D | Increased Pi
47
Autosomal dominant disorder that causes PTH resistance | - short, short neck, obese, short fingers
Albright hereditary osteodystrophy
48
Albright hereditary osteodystropy
Increased PTH, Pi | Decreased Ca, Vitamin D
49
Tumors that produce PTHrP that will bind the same receptor as PTH
Humerol hypercalcemia of malignancy
50
Humerol hypercalcemia of malignancy
Increased PTHrP, Ca | Decreased PTH, Pi, vitamin D
51
Autosomal dominant disorder that causes mutations in CaSR in the parathyroid glands and kidney
Familial hypocalciuric hypercalcemia (FHH)
52
Familial hypocalciuric hypercalcemia
Increased serum calcium | Decreased urine calcium
53
Vitamin D deficiency disorders?
Rickets and Osteomalacia
54
Growth failure and skeletal deformities in children
Rickets - vitamin D deficiency
55
Bone tenderness, fracture, bending and softening in adults
Osteomalacia
56
Type 1 rickets is due to?
Decreased 1alpha-hydroxylase

Neuroendocrine (47 decks)

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