Final answer:
Substance P is the neuropeptide neurotransmitter released from fibers that transmit sensory information about pain and temperature, acting on neurokinin receptors to modulate pain signals.
Step-by-step explanation:
The neuropeptide neurotransmitter that is released from fibers transmitting sensory information about pain and temperature is substance P. Substance P is part of the tachykinin family of neuropeptides and is the preferred endogenous ligand for the neurokinin (NK) receptor NK1, where it functions as both a neurotransmitter and a neuromodulator in the central and peripheral nervous system. It plays a significant role in the transmission of pain signals in the spinal cord's pain processing pathways.
Nociceptors, which are the type of receptor cell responsible for transducing pain stimuli as mentioned in the review questions, are activated by damaged tissues, which release chemicals that these receptor proteins respond to, initiating the sensation of pain.