Question

describe the sensory encoding of both a non-nociceptive thermoceptor and a nociceptive thermoceptor, as the intensity of a heat stimulus is increased in intensity from mildly cool, to painfully cold, then back to a normal temperature

Answer 1

A thermoceptor is the receptive portion of a sensory neuron that codes absolute and relative changes in temperature. It can also be classified as non-specialised sense receptor. These are located in the dermis, skeletal muscles, liver and hypothalamus and are activated by different temperatures.

Nociception can be defined as the sensory nervous system's response to certain harmful or potentially harmful stimuli. In this mechanism, stimulation of high intensity travels via the sensory nerve cells [nociceptors] along a chain of nerve fibers through the spinal cord to the brain.

Non-nociceptive pain is often dependent upon central sensitization induced by prior or ongoing nociception. Persistent pain is partially or wholly of non-nociceptive afferent origin.

Nociceptors have a certain threshold, i.e. they require a minimum intensity of stimulation before they trigger a signal. Nociception can also cause generalized autonomic responses before or without reaching conciousness.

Thermal nociceptors are activated by noxious heat or cold at various temperatures. When the temperature is mildly cold, the nociceptors are not activated. As the temperature becomes painfully cold, the specific nociceptor transducers are activated. The TRPM8 channels sense the cool stimuli. As the cold stimuli increases, the tactile sensibility and motor function deteriorate while pain perception persists. So, nociception results in sharp and sudden pain which go away while non- nociception results in persistent pain, may be due to tissue damage.

So, nociceptive thermoceptors will act swiftly, once activated while non-nociceptive thermoceptors will produce a longer lasting effect.