Question

what is one way that calcitonin and parathyroid hormone maintain homeostasis? a. calcitonin stimulates the bones to absorb calcium when calcium levels are too low, while parathyroid hormone stimulates the bones to absorb calcium when calcium levels are too high. b. calcitonin stimulates the kidneys to absorb calcium when calcium levels are too low, while parathyroid hormone stimulates the kidneys to excrete calcium when calcium levels are too high. c. calcitonin stimulates the kidneys to excrete calcium when calcium levels are too high, while parathyroid hormone stimulates the kidneys to absorb calcium when calcium levels are too low. d. calcitonin stimulates the bones to excrete calcium when calcium levels are too high, while parathyroid hormone stimulates the bones to absorb calcium when calcium levels are too low.

Explanation:

Calcitonin lowers blood - calcium levels when they are too high by stimulating the bones to absorb calcium. Parathyroid hormone raises blood - calcium levels when they are too low.

Answer:

A. Calcitonin stimulates the bones to absorb calcium when calcium levels are too low, while parathyroid hormone stimulates the bones to absorb calcium when calcium levels are too high. (This option is incorrect as parathyroid hormone stimulates bones to release calcium when levels are low).
B. Calcitonin stimulates the kidneys to excrete calcium when calcium levels are too high, while parathyroid hormone stimulates the kidneys to absorb calcium when calcium levels are too low. (This is correct. Calcitonin reduces blood - calcium by increasing renal calcium excretion when levels are high, and parathyroid hormone increases blood - calcium by promoting renal calcium reabsorption when levels are low).
C. Calcitonin stimulates the kidneys to excrete calcium when calcium levels are too low, while parathyroid hormone stimulates the kidneys to absorb calcium when calcium levels are too high. (Incorrect as calcitonin acts when levels are high, not low).
D. Calcitonin stimulates the bones to excrete calcium when calcium levels are too high, while parathyroid hormone stimulates the bones to absorb calcium when calcium levels are too low. (Bones do not excrete calcium in the way described; they can release or absorb it).

So the answer is B.