26. ______ Which of the following are direct target tissues of PTH? A. Bone B. S

Question

26. ______ Which of the following are direct target tissues of PTH?

      A. Bone

      B. Small intestine

      C. Kidney

      D. Both A and C

      E. All of the above

27. ______Which of the following would you expect to happen as a result of an inadequate

dietary intake of calcium?

A.   loss of bone mass

B.   retention of Ca2+ by the kidneys

C.   release of calcitriol by the kidneys

D.   increase absorption of calcium by the small intestines

E.   All of the above

28. ________Many different hormones circulate in the blood. What determines to which

      hormone a tissue will respond?

      A. the concentration of hormones in the ECF

      B. the specific receptors found on the cells of a tissue

      C. the chemical nature of the hormone

      D. All of the above.

Explanation / Answer

26.

Parathyroid hormone (PTH) and calcitonin are the two hormones that regulate blood calcium levels. PTH is secreted by the parathyroid gland, PTH increases the calcium levels of plasma and extra cellular fluid by increasing the absorption of calcium from gastrointestinal tract, renal tubules, and by increasing the calcium desorption from bones.

Calcitonin is secreted by the parafollicular cells of the thyroid gland and it is involved in the metabolism of calcium and phosphorus calcitonin has opposite effects to that of PTH.

Thus, the correct option is E. All of the above

27. E.   All of the above

28. B. the specific receptors found on the cells of a tissue.

A hormone specifically binds to only one type of receptor (lock and key mechanism).

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