Final answer:
Substance P neurotransmitter is primarily responsible for the transmission of nociception, but also plays roles in the regulation of emotions such as depression, anxiety, and stress in various areas of the brain.
Step-by-step explanation:
The substance P neurotransmitter (SP) is responsible for a variety of functions in the body, acting as a neurotransmitter and a neuromodulator in both the central and peripheral nervous systems. Its most notable role is in the transmission of nociception, the sensory perception of pain. SP is a member of the tachykinin peptide family and serves as the preferred endogenous ligand for the neurokinin (NK) receptor, specifically NK1. This substance plays a significant role in the modulation of pain in the spinal cord pathways. Additionally, in the brain, SP is involved in the regulation of emotions, as it is expressed in areas related to depression, anxiety, stress, as well as motivation and reward.