Question:

Describe in detail the negative feedback mechanism of regulating blood calcium levels with emphasis on the role that osteoblast and osteoclast activity is affected by hormones.

Answer:

Calcium levels are maintained strictly within the body in the range of 9-11mg per 100ml. The parathyroid gland releases the parathyroid hormone when blood levels of ionic calcium decline. It stimulates osteoclasts, the bone breakers, to destroy bone matrix, releasing calcium into the bloodstream. When calcium concentration in the blood rises to normal levels, the stimulus for parathyroid hormone release ends. When blood calcium levels rise, calcitonin is released by the thyroid gland. Calcitonin stimulates calcium deposits in bone and inhibits osteoclasts from breaking down bone. Osteoblasts are stimulated to make more bone tissue. As these things happen blood calcium levels reduce to normal and the stimulus ends.

Instructor Comments:

Student concisely and directly addresses entire question.
Factual information is clearly stated and correct.
No vague references or inconsistent statements.
Good sentence structure, grammar, spelling and punctuation - very few mistakes.