Blood calcium must be tightly regulated to prevent health pr…

Blood calcium must be tightly regulated to prevent health problems. In the case of low blood calcium, chemoreceptive cells within the parathyroid glands detect the drop in Ca2+. This signals the synthesis of the hormone calcitriol. Calcitriol enters the blood, and encourages the uptake of calcium along the intestine, inhibits the loss of calcium in the urine, and encourages osteoclasts to resorb bone and release calcium into the blood, leading to a return to homeostasis.   In this example, what structure is the receptor? 

Blood calcium must be tightly regulated to prevent health pr…

Blood calcium must be tightly regulated to prevent health problems. In the case of low blood calcium, chemoreceptive cells within the parathyroid glands detect the drop in Ca2+. This signals the synthesis of the hormone calcitriol. Calcitriol enters the blood, and encourages the uptake of calcium along the intestine, inhibits the loss of calcium in the urine, and encourages osteoclasts to resorb bone and release calcium into the blood, leading to a return to homeostasis.   What structure is the control center?