The Endocrine System, Control of Hormone release
Hormones can be classified by their reflex pathways. Endocrine Cell Is the sensor in the Simplest Endocrine Response The endocrine gland acts as both the sensor (receptor) and the integrating sensor. PTH is an example, so is insulin and glucagon. Parathyroid endocrine cells monitor blood calcium levels, from its four clusters behind the thyroid. Calcium concentration is monitored with the aid of G-Protein-coupled calcium receptors on their cell membrane. When certain number of Receptors are bound to Calcium, PTH is inhibited. If the plasma calcium falls below a certain level and fewer receptors are bound to Calcium, inhibition ceases and the parathyroid cells secrete PTH. PTH released in the blood, effect on increased bone resorption, increased kidney reabsorption of calcium, and production of calcitrol leads to increased intestinal absorption of calcium. Together this increases the plasma calcium concentration. Many endocrine Reflexes involve the Nervous System Two endocrin...