Question 1

The vitamin D receptor belongs to which class of receptors?&#10;A)G protein-coupled receptors&#10;B)Tyrosine kinase receptors&#10;C)Nuclear hormone receptors&#10;D)Calcium-sensing receptors&#10;E)Janus kinase/signal transducer and activator of transcription (JAK/STAT)receptors

Accepted Answer

The vitamin D receptor (VDR) is a type of nuclear hormone receptor. Nuclear hormone receptors are a class of transcription factors that bind to DNA in the nucleus and regulate gene expression in response to small (lipid-soluble) hormone molecules.

Question 2

The parathyroid glands respond rapidly to hypocalcemia.The protein responsible for the rapid response of the principal cells to a falling calcium level is: A)The PTH receptor. B)Membrane Ca⁺⁺-adenosine triphosphatase (ATPase). C)Ca⁺⁺-sensing receptor. D)The Na⁺-Ca⁺⁺ exchange antiporter. E)The transient receptor potential cation channel subfamily V,member 5 (TRPV5)calcium channel.

Accepted Answer

The Ca⁺⁺-sensing receptor is responsible for the rapid response of the principal cells in the parathyroid gland to a falling calcium level. When the calcium level in the blood drops, the Ca⁺⁺-sensing receptor activates the principal cells to secrete parathyroid hormone (PTH), which then acts on the bones, kidneys, and intestines to increase the release of calcium into the blood. The other options listed are not responsible for the rapid response of the principal cells to hypocalcemia.

Question 3

Lack of vitamin D can cause rickets in children.Of the following,which is the most important lifestyle activity that promotes normal endogenous vitamin D production?&#10;A)Playing outside.&#10;B)Exercising at a gym.&#10;C)Eating green vegetables.&#10;D)Consuming highly unsaturated oils (e.g.,olive oil).&#10;E)Drinking fruit juices.

Accepted Answer

Playing outside promotes natural sunlight exposure, which triggers the body to produce vitamin D. This is the most effective lifestyle activity for promoting endogenous vitamin D production, as opposed to consuming vitamin D fortified foods or supplements.

Question 4

Endogenous vitamin D synthesis begins in:&#10;A)The intestines.&#10;B)The kidneys.&#10;C)The liver.&#10;D)The skin.&#10;E)Bone tissue.

Accepted Answer

Endogenous vitamin D synthesis begins in the skin, specifically in the epidermal layer. When skin is exposed to UVB radiation from sunlight, a form of cholesterol in the skin is converted to Vitamin D3. This form of Vitamin D then undergoes further activation in the liver and kidneys.

Question 5

Estrogen can oppose some of the effects of PTH.This occurs because of the effects of estrogen on:&#10;A)Intestinal enterocytes.&#10;B)Osteoclasts.&#10;C)Osteoblasts.&#10;D)Chief cells of the parathyroid gland.&#10;E)Proximal renal tubule cells.

Accepted Answer

Estrogen can reduce the resorptive activity of osteoclasts, thereby opposing the bone resorption effect of parathyroid hormone (PTH).

Question 6

Osteoporosis can result from excessive production of receptor activator of nuclear factor $\kappa$ light-chain enhancer of activated B cells (RANK)ligand (RANKL)by osteoblasts.A molecule that directly inhibits RANKL and protects bones from osteoclast overactivity is:

A)PTH.
B)Osteoprotegerin.
C)Alkaline phosphatase.
D)Osteoid.
E)RANK.

Accepted Answer

Osteoprotegerin (OPG) is a molecule that directly inhibits RANKL, which is responsible for osteoclast overactivity. By inhibiting RANKL, OPG can protect bones from excessive osteoclast activity and prevent osteoporosis. PTH, alkaline phosphatase, osteoid, and RANK are not direct inhibitors of RANKL and do not have the same protective effect on bones.

Question 7

PTH is secreted in a regulated manner.Which of the following directly increases PTH synthesis,secretion,or both? A)Elevated 1,25-dihydroxyvitamin D B)Decreased blood phosphate levels (hypophosphatemia) C)Decreased blood Ca⁺⁺ levels (hypocalcemia) D)Elevated blood K⁺ levels (hyperkalemia) E)Elevated Mg⁺⁺ levels (hypermagnesemia)

Accepted Answer

The answer of PTH is secreted in a regulated manner.Which...

Deck 40: Hormonal Regulation of Calcium and Phosphate Metabolism