Final answer:
The rhythmicity center that sets the rhythm of automatic breathing is located in the Medulla oblongata. It stimulates the diaphragm and intercostal muscles to contract for inspiration and allows them to relax for expiration. The VRG in the medulla oblongata is involved in forced breathing.
Step-by-step explanation:
The rhythmicity center that sets the rhythm of automatic breathing is located in the Medulla oblongata.
The medulla oblongata contains the dorsal respiratory group (DRG) and the ventral respiratory group (VRG). The DRG is involved in maintaining a constant breathing rhythm by stimulating the diaphragm and intercostal muscles to contract, resulting in inspiration. When activity in the DRG ceases, it no longer stimulates the diaphragm and intercostals to contract, allowing them to relax, resulting in expiration. The VRG is involved in forced breathing, as the neurons in the VRG stimulate the accessory muscles involved in forced breathing to contract, resulting in forced inspiration. The VRG also stimulates the accessory muscles involved in forced expiration to contract.