Bone Disease Part 1

Question 1

What and when is PTH released

Answer 1

Released by parathyroid gland in response to low plasma Ca2+

Question 2

what 3 things does PTH cause

Answer 2

Causes:

• Increased Ca2+ release from bone by affecting osteoblast and osteoclast activity
• Increased resorption of Ca2+ from kidneys
• stimulates formation and secretion of calcitriol (active Vitamin D) by the kidneys

Question 3

3Why is the PTH control of calcium balance a negative feedback loop

Answer 3

As the serum calcium concentration increases, signals are sent to the parathyroid gland to stop producing PTH

Question 4

What is bone resorption stimulated by

Answer 4

Parathyroid hormone (PTH)

Question 5

5. What cells is receptors for PTH found on

Answer 5

The receptors for PTH are located on osteoblasts

Question 6

6. What receptors do osteoclast precursors have on their cell membranes

Answer 6

have RANK receptors on their cell membranes

Question 7

7. What ligand is on the membrane of osteoblasts

Answer 7

RANKL

Question 8

8. Outline the relationship between osteoblasts and osteoclasts starting with PTH

Answer 8

1. PTH binds to PTH receptors on Osteoblasts, causing Osteoblasts to present RANKL on their cell surface membrane.
2. RANKL on osteoblasts binds to RANK receptors on osteoclast precursor cells, activating the cell to become an osteoclast.

Question 9

9. What do osteoblasts also produce which prevents resorption by binding to RANKL

Answer 9

osteoprotegrin

Question 10

10. What does the ratio of RANKL:osteoprotegrin determine

Answer 10

It determines the rate of bone resorption