Chapter 6 introduced an essential part of the cell: the. plasma membrane. Thanks to the selective permeability of. phospholipid bilayers and the activity of membrane trans-. port proteins, this structure creates an internal environment. that is different from conditions outside the cell. Our task.
When calcium levels decrease, this stimulates the parathyroid gland to release parathyroid hormone. Parathyroid hormone encourages the normal process of bone breakdown (essential for maintenance and growth of the bone). This process of bone breakdown releases calcium into the bloodstream.
Parathyroid hormone opposes the effect of calcitonin, a hormone  produced by the thyroid gland that regulates calcium levels. It  removes calcium from its storage sites in b â¦ ones and releases it  into the bloodstream.alcitonin slows the release of calcium from bones into  bloodstream, thereby keeping blood levels of calcium to a minimum.    Parathyroid hormone does the opposite.