Unit 2 - Calcium

Question 1

What are the main physiologic functions of Ca?

Answer 1

muscle contraction, hormone and neurotransmitter release, second messenger, coagulation, structural component of bone

Question 2

What processes in the gut contribute to levels of Ca in plasma?

Answer 2

calcium is absorbed in the GI tract from the diet into the plasma

Question 3

What processes in the bone contribute to levels of Ca in plasma?

Answer 3

Ca is sent to the bone for storage and accretion

Question 4

What processes in the kidney contribute to levels of Ca in plasma?

Answer 4

Ca is sent to the kidney to be filtered and then can be reabsorbed back into the plasma if needed

Question 5

What hormones contribute to the regulation of calcium homeostasis?

Answer 5

PTH (parathormone), vitamin D, and calcitonin

Question 6

What hormones increase plasma levels of Ca?

Answer 6

PTH and Vitamin D

Question 7

What hormone decreases plasma levels of Ca?

Answer 7

calcitonin

Question 8

What is the chemical nature of parathormone?

Answer 8

it is a protein

Question 9

What is parathormone secreted by?

Answer 9

chief cells of the parathyroid gland

Question 10

What is the secretion of parathormone triggered by and what is the trigger sensed by?

Answer 10

a decrease in serum ionized Ca which is detected by calcium-sensing receptors in the membranes of chief cells

Question 11

What does parathormone stimulate?

Answer 11

osteoclasts to begin bone resorption to increase plasma Ca, increase renal vitamin D activation, increase renal Ca resortion and decrease renal PO4 reabsorption

Question 12

How is vitamin D synthesized (3 steps)?

Answer 12

1. Vitamin D can either come from food, or UV light turns cholesterol into vitamin D3 (cholecalciferol)
2. Vitamin D3 is synthesized into 25(OH)D3 in the liver and then is sent to the kidney
3. PTH stimulates the synthesis of 1,25(OH)2D3 from 25(OH)D3

Question 13

What is the main of Vitamin D?

Answer 13

increase Ca and PO4 intestinal absorption

Question 14

What are secondary functions of vitamin D?

Answer 14

increase Ca and PO4 renal reabsorption and increase bone resorption

Question 15

What is the chemical nature of calcitonin?

Answer 15

32 amino acid peptide

Question 16

What is calcitonin secreted by?

Answer 16

the thyroid gland

Question 17

What is calcitonin secreted in response to?

Answer 17

hypercalcemia

Question 18

What triggers calcitonin secretion?

Answer 18

high plasma calcium and gastrin

Question 19

What are the main functions of calcitonin?

Answer 19

decrease of Ca intestinal absorption, resporption from bone, renal reabsorption

Question 20

What are the common causes of hypercalcemia?

Answer 20

primary hyperparathyroidism and vitamin D toxicosis

Question 21

Generally, what is a main sign of hypercalcemia?

Answer 21

decreased neuromuscular excitability

Question 22

What are the treatments for hypercalcemia?

Answer 22

volume expansion, loop diuretics

Question 23

What are the common causes of hypocalcemia?

Answer 23

primary hypoparathyroidism and renal failure

Question 24

Generally, what is a main sign of hypocalcemia?

Answer 24

increased neuromuscular excitability

Question 25

What are the treatments for hypocalcemia?

Answer 25

IV calcium gluconate, oral calcium, vitamin D

Question 26

Why does calcium affect neuromusclular excitability?

Answer 26

because the role of calcium is to block sodium channels, the amount of it depends on the effect it will have

Question 27

How does low levels of calcium effect depolarization?

Answer 27

it makes it easier

Question 28

How does high levels of calcium effect depolarization?

Answer 28

it makes it harder