Calcium Homeostasis Flashcards Preview

Regulatory Physiology and Pharmacology > Calcium Homeostasis > Flashcards

Flashcards in Calcium Homeostasis Deck (26):
1

What are the roles of calcium?

bone and teeth rigidity
muscle contraction
membrane stability
NT release
secretory process
DNA/RNA synthesis
blood clotting
enzyme regulation

2

What can result due to hypocalcemia?

the nervous system becomes more excitable causing tetanic muscle contraction and cramps
osteoporosis
rickets and osteomalacia

3

What can result with hypercalcemia?

moans - constipation, abd pain, nausea
stones - kidney stones, frequent peeing
groan - confusion, dementia, memory loss, depression
bones - bone aches, pains, fractures
also abnormal heart rhythms, and cardiac malfunction

4

What are the primary regulators of calcium balance?

PTH, Calcitonin and Vit D

5

Where is PTH manufactured?

chief cells of PT glands

6

What is the target organs of PTH?

bone and kidney

7

What is the action of PTH?

hypercalcaemia

8

Why is a thyroid ectomy not fatal?

because there are small clusters of PTH producing cells outside the PT gland

9

How is PTH secretion controlled?

an EC calcium sensing receptor
High Ca prevents PTH secretion

10

How does high Ca prevent exocytosis of PTH granules?

activates PLC which inhibits AC
generates IP3 which decreases cAMP

11

What results from hyperparathyroidism?

bone resorption, intestinal Ca absorption and renal tubular reabsorption
related to excessive Vit D3

12

What can cause hyperparathyroidism?

adenomatous or hyperplastic parathyroid tissue

13

What causes hypoparathyroidism?

inadequate response of VitD-PTH axis to hypocalcaemic stimuli

14

What is the effect of calcitonin on bone?

decreased activity of osteoclasts and osteoblasts

15

What effect does calcitonin have on VitD?

increases production of inactive version

16

What is calcitonin released in response to?

rising circulating Ca

17

What is the target cell of calcitonin?

the osteoclast

18

What is the effect of calcitonin on the osteoclast?

increases cAMP concentrations which inhibits osteoclast motility, changes their shape and inactivates them

19

What is the major effect of calcitonin?

rapid fall in Ca caused by inhibition of bone resorption

20

Where is VitD acquired from?

sun and diet

21

Why is VitD not a classic hormone?

because it is not produced or secreted by an endocrine gland

22

Where is VitD converted to its active form?

through the liver and then the kidney

23

What does VitD do in the bone?

activates both osteoblasts and osteoclasts increasing the rate of bone remodelling but with little net effect on bone present

24

What is the effect of VitD in the GI?

increases GI calcium and phosphate absorption and renal calcium reabsorption

25

What does active Vit D bind to?

a typical nuclear receptor

26

What does it travel in the blood bound to and why?

it is lipid soluble so travels bound to hydroxylated a-globulin