Final answer:
Sensory fibers are responsible for reacting to stimuli such as heat, cold, touch, pressure, and pain. Free nerve endings in the skin are particularly sensitive to painful and thermal stimuli, and they transmit these signals as electrical signals through the nervous system.
Step-by-step explanation:
The nerve fibers that react to heat, cold, touch, pressure, and pain are sensory fibers.
The specific receptors for these stimuli are classified as somatosensory receptors, which include mechanoreceptors for touch and pressure, thermoreceptors for heat and cold, and nociceptors for pain.
When the epidermis is burned, it is primarily the free nerve endings that are affected, as they are the most common nerve endings in the skin and extend into the middle of the epidermis.
These nerve endings are sensitive to painful stimuli and to extreme temperatures.
Additionally, the pain and temperature signals, after transduction, travel as electrical signals through the nervous system.
In the case of heat associated with spicy foods, molecules like capsaicin can activate certain nociceptors, indicating how chemical stimuli can induce a sensation of pain or heat.