Final answer:
Sever or traumatic pain causes the body to release chemical messengers and activate nociceptors, resulting in a pain signal transmitted to the central nervous system. The body also undergoes vascular spasm and forms a platelet plug in response to severe or traumatic pain.
Step-by-step explanation:
Pain is caused by trauma at the cellular level, which triggers the release of chemical messengers such as cytokines, serotonin, and prostaglandins. These messengers activate nociceptors, which are receptors for pain, and transmit the pain signals to the central nervous system. The body's response to sever or traumatic pain includes vascular spasm and the formation of a platelet plug.