The Skeletal System: Regulation of Blood Calcium Concentrations

Most of the calcium in the body is stored in __________ tissue.

bone

Bone tissue contains __________% of the calcium in the body.

99

The normal range for blood calcium concentrations is __________ to __________ mg Ca2+ /dL of blood.

8.5, 11

When blood calcium concentrations drop below 8.5 mg Ca2+ /dL, this stimulates __________ cells to secrete Parathyroid hormone (PTH).

Parathyroid

PTH increases __________ activity and decreases __________ activity, which causes an increase in bone resorption.

osteoclast, osteoblast

PTH increases calcium absorption in the __________.

small intestine

PTH inhibits the loss of calcium in __________ at the kidneys.

urine

When blood calcium concentrations rise above 11 mg Ca2+ /dL, this stimulates __________ cells in the thyroid gland to secrete Calcitonin (CT).

C

Calcitonin inhibits __________ activity, decreasing bone resorption.

osteoclast

Calcitonin reduces calcium absorption in the __________.

small intestine

Calcitonin stimulates the loss of calcium from the blood into __________ in the kidneys.

urine

The body uses __________ feedback loops to keep blood calcium concentrations within a narrow range.

negative

PTH travels through the bloodstream binding to __________ in multiple locations.

receptors

Increased bone resorption releases calcium from __________ tissue into the bloodstream.

bone

Calcitonin decreases bone resorption and increases bone __________.

production

PTH is responsible for increasing blood calcium concentrations by stimulating __________ activity.

osteoclast

Calcitonin acts to __________ blood calcium concentrations when they are too high.

decrease

The hormone secreted by Parathyroid cells when blood calcium is low is __________ hormone (PTH).

Parathyroid

Calcitonin is secreted by __________ cells in response to high blood calcium levels.

C

The range for normal blood calcium concentrations indicates low levels below __________ mg Ca2+ /dL should trigger a hormonal response.

8.5

Bone tissue can release calcium through __________, allowing it to enter the bloodstream.

bone resorption