Be careful with the two examples below. Remember that the control center does not have to be the
brain, it can be any organ. Sometimes different sides of the homeostatic loop may have a different
control center. This organ can communicate with the effectors using hormones.
Homeostatic Control of Blood Glucose:
Blood Glucose levels are normally 90mg/100ml of blood. This level is controlled by two hormones....
1. Insulin that is released by the pancreas and causes the liver to convert glucose to glycogen
2. Glucagon that is released by the pancreas and causes the liver to convert glycogen to glucose
Diagram the homeostatic loop control mechanism for blood glucose showing how the body responds to
changes in calcium levels. Try and label as many of the lines as possible indicating how various parts
of the control mechanism communicate with each other. (20)
Homeostatic Control of Blood Calcium:
Blood calcium levels are controlled by two hormones
1. Calcitonin, released by the thyroid gland that stimulates calcium removal from the blood and
deposition in the bone.
2. Parathyroid hormone (PTH) released by the parathyroid glands that breaks down bone cells and
releases calcium into the blood. PTH also simulates the kidneys and intestines to absorb more
calcium into the blood
Diagram the homeostatic loop control mechanism for blood calcium showing how the body responds to
changes in calcium levels. Try and label as many of the lines as possible indicating how various parts
of the control mechanism communicate with each other. (20)