Question

complete each sentence describing the hormonal control of calcium homeostasis. labels can be used more than once.

1. when levels of blood calcium (click to select), parathyroid hormone is released from the parathyroid glands located on the posterior side of the
2. parathyroid hormone

(click to select) and
of

1. as a result of direct

kidneys, parathyroid
calcium levels.
he and
blood

1. when blood levels of calcium (click to select), calcitonin is released from cells in the thyroid gland.
2. calcitonin causes an increase in the number of (click to select) and greater rates of bone deposition.
3. as a result of direct actions on the target cells of bone and kidneys, calcitonin works to (click to select) blood calcium levels.

Explanation:

Identify the physiological feedback loops

The sentences describe the hormonal control of calcium homeostasis, which is regulated by a negative feedback loop involving two main antagonistic hormones: parathyroid hormone (PTH) and calcitonin.

Analyze parathyroid hormone regulation

• Sentence 1: Parathyroid hormone (PTH) is released when blood calcium levels are low to restore balance. Therefore, when levels of blood calcium decrease, PTH is released from the parathyroid glands located on the posterior side of the thyroid gland.
• Sentence 2: PTH acts to raise blood calcium. It stimulates osteoclasts to resorb bone and promotes calcium reabsorption in the kidneys. Thus, PTH stimulates an increase in the number of osteoclasts and greater rates of bone resorption.
• Sentence 3: As a result of these direct actions on the target cells of bone and kidneys, PTH works to increase blood calcium levels.

Analyze calcitonin regulation

• Sentence 4: Calcitonin is released when blood calcium levels are high to lower them. Therefore, when blood levels of calcium increase, calcitonin is released from parafollicular cells in the thyroid gland.
• Sentence 5: Calcitonin acts to lower blood calcium by inhibiting bone resorption and promoting deposition. Thus, it causes an increase in the number of osteoblasts and greater rates of bone deposition.
• Sentence 6: As a result of these direct actions on target cells, calcitonin works to decrease blood calcium levels.

Verify the complete sentences

Let's double-check the logical flow of each completed sentence to ensure physiological accuracy:

1. When blood calcium decreases, PTH is released. (Correct)
2. PTH increases osteoclasts to resorb bone. (Correct)
3. PTH actions increase blood calcium levels. (Correct)
4. When blood calcium increases, calcitonin is released. (Correct)
5. Calcitonin increases osteoblasts to deposit bone. (Correct)
6. Calcitonin actions decrease blood calcium levels. (Correct)

Answer:

Question 1

When levels of blood calcium <blank>decrease</blank>, parathyroid hormone is released from the parathyroid glands located on the posterior side of the thyroid gland.

Question 2

Parathyroid hormone stimulates an increase in the number of <blank>osteoclasts</blank> and greater rates of bone resorption.

Question 3

As a result of direct actions on the target cells of bone and kidneys, parathyroid hormone works to <blank>increase</blank> blood calcium levels.

Question 4

When blood levels of calcium <blank>increase</blank>, calcitonin is released from cells in the thyroid gland.

Question 5

Calcitonin causes an increase in the number of <blank>osteoblasts</blank> and greater rates of bone deposition.

Question 6

As a result of direct actions on the target cells of bone and kidneys, calcitonin works to <blank>decrease</blank> blood calcium levels.