Calcium Homeostasis chapter 6

Control Center

Parathyroid hormone gene (control center) detects the increase in cyclic AMP (the input)

What is a normal blood calcim level

9 and 11mg/100mL

Where is Calcium store?

Bone is the major calcium reservoir, storing 99% of total body calcium

calcitonin

Hormone produced by the thyroid that reduces blood calcium levels. Calcitonin is harvested from salmon and is an effective drug for treating osteoporosis.

A stimulus causes blood calcium levels to decrease___.

PTH cells receptors detect change and increases their production of a molecule (cyclic AMP) "input".

Output

PTH gene is turned on which increases release of PTH.

parathyroid hormone

a hormone that increases osteoclast activity to release more calcium ions into the bloodstream via negative feedback.

Effectors

as a result more PTH is released into the blood. The presence of PTH increases the number of osteoclast (effector), which steps up the pace of bone resorption, the result of calcium being release from bone into the blood returns the blood calcium to normal level.

why is calcium important?

both nerve and muscles cells depend on a stable level of calcium ions to function properly. Blood clotting require calcium, enzyme require calcium as cofactors.

How can changes in blood calcium be fatal?

heart may stop (cardiac arrest) if levels are to high, breathing may cease if levels fall to low.

the role of bone in calcium homeostasis

is to help buffer the blood calcium level, by releasing calcium into blood plasma (using osteoclasts) when blood calcium level decreases. absorbing calcium (using osteoblast) when the level rises.

How is calcium level maintain in the body?

maintain by two ways, by controlling the rate of calcium resorption from bone into blood (osteoclast) and the rate of calcium deposition from blood into bone (osteoblast)

What Hormone works to decrease blood Calcium level, when blood calcium rises above normal?

parafollicular cells in the thyroid gland secrete calcitonin (CT) that works to decrease blood calcium level. CT inhibits osteoclast and speeds up osteoblast and deposition of calcium into the bones. Net result is bone formation and decrease in blood calcium level.

Calcium exchange is monitored by __________

parathyroid hormone (PTH)