Calcium Homeostasis (physiology) Flashcards

1
Q

What stimulates the release of PTH??

A

Low blood calcium levels

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2
Q

In which cells is calcitonin released and what stimulates the release?

A

In the parafollicular cells, high calcium levels

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3
Q

What do we call the stimuli caused by ions, nutrients and chemicals?

A

Humoral stimuli

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4
Q

What are the two bone cells and their antagonistic functions?

A

Osteoblasts- resp for calcium deposition in bone.
Osteoclasts- resp for bone resorption in order to produce calcium and phosphate ions.

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5
Q

What are some of the functions of calcium?(5)

A

Contraction of muscle cells.
Cell proliferation
Mineralization of bones and teeth.
Tight junctions
Blood clotting

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6
Q

What are the three forms of circulating calcium?(3)

A

Ionized from- most biologically active form.
(50%)
Protein bound- Bound to negatively charged albumin. (40%)
Complexes form- bound to substances such as citrate and phosphate. (10%)

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7
Q

What are the cells resp for production of PTH?

A

Chief cells of the parathyroid gland

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8
Q

Two disorders of the parathyroids, explain further.(4)

A

Hyperparathyroidism:
- Tumour of parathyroid gland.
- Increased levels of PTH, caused high calcium levels.
- Weakening of bones, softening of bones, muscle weakness and kidney stones formation.

Hypoparathyroidism:
-Mostly due to accidental removal of parathyroid glands.
-Low levels of PTH, causes low levels of calcium.
- Tetany, suffocation, spams of laryngeal muscles.

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9
Q

What are the causes of vitamin d deficiency?(4)

A

Reduced exposure to the sun.
Poor dietary intake
Malabsorption
Vitamin D metabolism abnormality

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10
Q

Which other hormone stimulates osteoclast-mediated resorption of bone?

A

Thyroxine

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11
Q

How does oestrogen and testosterone affect ca metabolism?

A

They inhibit osteoclast function, and stimulate osteoblast function.

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12
Q

What role does cortisol play in ca metabolism?

A

It inhibits intestinal absorption and stimulate renal elimination.

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13
Q

What role does GH play in ca metabolism?

A

It increases urinary excretion of ca, while decreasing the urinary excretion of phosphate.

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14
Q

What are the causes of hypercalcaemia?

A

Thyrotoxicosis
Renal failure
Drug induced
Iatrogenic
Malignancy

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15
Q

What are the hypothyroid causes of hypocalcaemia?(5)

A

Post operative
Idiopathic
Acquired hypomagnesaemia
Neck irritation
Anticonvulsive therapy

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16
Q

What are the non-parathyroid causes of hypocalcaemia?(5)

A

Vitamin D deficiency
Vitamin D resistance
Renal disease
Malabsorption
Hypophosphataemia

17
Q

What are the PTH resistance causes of hypocalcaemia?

A

Pseudo-hypoparathyroidism
Hypomagnesaemia

18
Q

What is osteoporosis?

A

Reduction of bone mineral density

19
Q

What are the factors increasing the risk of osteoporosis?(7)

A

Premature menopause
Smoking
Poor calcium intake
Inactivity, immobilization
Excessive caffeine intake
High alcohol intake
Excessive exercise