Physiology Calcium Homeostasis and Regulation

Question 1

What is calcium homeostasis regulated by?

Answer 1

The effects of PTH and 1,25-dihydroxyvitamin D3 on the gut, kidney and bone

Question 2

Where are calcium-sensing receptors present?

Answer 2

The parathyroid glands, kidney and brain

Question 3

What does calcium consumption primarily come from?

Answer 3

Dairy foods

Question 4

What is the primary source of Vitamin D in humans?

Answer 4

Photoactivation in the skin of 7-dehydrocholesterol to cholecalciferol

Question 5

What roles do the liver and kidney play in cholecalciferol conversion?

Answer 5

• Cholecalciferol is then converted into 25-hydroxyvitamin D by the liver, which is then converted into 1,25-dihydroxyvitamin D3 in the kidney

Question 6

What regulates conversion of 25-hydroxyvitamin D conversion to 1,25-dihydroxyvitamin D3?

Answer 6

Regulation of 25-hydroxyvitamin D conversion to 1,25-dihydroxyvitamin D3 is by PTH, phosphate and feedback inhibition by 1,25-dihydroxyvitamin D3

Question 7

How does PTH increase plasma calcium?

Answer 7

-Increases osteoclastic activity in bone
-Increases intestinal absorption of calcium