Explain why two sensations (e.g. first and second) can be elicited by activation of nociceptors? How do these sensations differ?

• Pain is sensed in two phases, the first very fast one is conducted via A-fibers and the second slower one by C-fibers.
• Pain transmitted by C-fibers is unlocalized due to peptidergic transmitters (e.g. Substance P which enhances and prolong action of glutamate).