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Post your work relating to the homeostatic system you investigated.
You can put links to powerpoint files or images of the posters you created.

Back to Friday 20th March lesson

Calcium Regulation (in the blood)
Basic information:
There are two types of cells that regulate calcium uptake by the bone and the breakdown of bone to release calcium. These are osteoclasts and osteoblasts. Osteoclasts break down bone to release calcium into the blood. Osteoblasts take calcium in the bone and use it to create new bone.

  • Calcium levels in the blood increase because I just drank a 2L carton of milk.
  • Certain cells in the thyroid gland are triggered by increased calcium levels (sorry for lack of detail)
  • When those cells in the thyroid gland are triggered, the hormone calcitonin is released from the thyroid gland into the blood stream.
  • Calcitonin travels to bone cells
  • Calcitonin decreases the activity of osteoclasts creating a net uptake of calcium from the blood because osteoblasts now outnumber osteoclasts.
  • This uptake of calcium lowers calcium levels in the blood.


Basic information:

When calcium levels in the blood are adequate, the receptors in the parathyroid gland are activated. When activated, they inhibit the synthesis and release of the parathyroid hormone (PTH). When calcium levels drop, the receptors are not activated and so synthesis and release of PTH occurs.

  • Calcium levels in the blood decrease because every time I drink milk, I visualise a cow having its teats squeezed by a farmer who hasn’t washed is hands for four days. As a result, I’ve stopped drinking milk.
  • With less calcium in the blood, receptors in the plasma membrane of the parathyroid cells are not activated, so PTH is produced and released into the blood stream.
  • PTH travels to bones cells and binds to osteoblasts
  • Osteoblasts then release cytokines which produce more osteoclasts and enhance their activity – thereby creating more osteoclasts than osteoblasts.
  • Osteoclasts then break down the bone to release calcium into the blood
  • This increases calcium levels in the blood

Voj, I uploaded our worksheet on blood pressure regulation to the homeostasis presentation page. Adam
Thx for that Adam Can you also upload your presentation as well. VM
Don't have a finished copy of it, but I will make sure we get one up. AK

Blood Pressure Regulation Worksheet.

Blood Pressure Regulation PowerPoint.