Image 1 (IMAGE) The University of Hong Kong Caption Schematic diagram showing the skeletal interoceptive circuit revealed in this work: the divalent metal cations can trigger the production of PGE2 from macrophages, which activates the afferent sensory nerves to initiate the CNS control of new bone formation through the sympathetic nervous system. Credit The University of Hong Kong Usage Restrictions This work is licensed for non-commercial, non-exclusive, one-time usage with attribution to the copyright holder. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.