Involves physical activation of nociceptive pathways without subjective emotional experience of pain.

May occur without cortical involvement or conscious pain such as a reflex response to a noxious stimulus.

Involves peripheral sensory receptors with afferent fibers that synapse in the spinal cord on interneurons, which synapse on motor neurons (that are also in the spinal cord which trigger muscle flexion contractions away from the stimulus.



Nociception refers to the sensory nervous system’s process of encoding noxious stimuli. 



In nociception, chemical, mechanical or thermal stimulation of sensory nerve cells called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain.



Nociception triggers physiological and behavioral responses and usually results in a subjective experience, or perception, of pain.



Damaging mechanical, thermal, and chemical stimuli are detected by nerve endings called nociceptors.



Nociceptors are found in the skin, on internal surfaces such as the periosteum, joint surfaces, and in some internal organs. 



Some nociceptors are free nerve endings with their cell bodies outside the spinal column in the dorsal root ganglia.



Some nociceptors rely on specialized structures in the skin to transduce noxious information such as nociceptive schwann cells.



After nerve injury touch fibers that normally carry non-noxious stimuli to be perceived as noxious.



Nociceptors require a minimum intensity of stimulation before they trigger a signal that is passed along the axon of the neuron into the spinal cord.


Excitation of pain fibers becomes greater if the pain stimulus continues, leading to hyperalgesia.


Nociception can also cause generalized autonomic responses before or without reaching consciousness: causing pallor, sweating, tachycardia, hypertension, lightheadedness, nausea and fainting.


Proprioception is determined mechanoreceptors, especially stretch ruffini corpuscles and transient receptor potential channels.


Proprioception is within the somatosensory system.


Thermoception refers to stimuli of moderate temperatures 24-28°C (75-82°F).


Temperatures beyond that range as is considered pain and moderated by nociceptors. 


Transient receptor potential  and potassium channels each respond to different temperatures.


They  create action potentials in nerves which join the touch system in the posterolateral tract. 


Thermoception, like proprioception, is then covered by the somatosensory system.


Transient receptor potential (TRP) channels that detect noxious stimuli  of mechanical, thermal, and chemical pain, relay that info to nociceptors that generate an action potential. 


Mechanical transient receptor potential channels react to depression of their cells with touch, thermal TRP change shape at different temperatures, and chemical TRP act like taste buds, signalling if their receptors bond to certain elements/chemicals.


The amygdala and hippocampus create and encode the memory and emotion due to pain stimuli.


The hypothalamus signals for the release of hormones that make pain suppression more effective; some of these are sex hormones.


The  lateral spinothalamic tract aids in localization of pain.


The  spinoreticular and spinotectal tracts are relay tracts to the thalamus that aid in the perception of pain and alertness towards it. 


Pain fibers cross over via the spinal anterior white commissure.


The lateral lemniscus is the first point of integration of sound and pain information.


The inferior colliculus (IC) aids in sound orienting to pain stimuli.


The superior colliculus receives inferior colliculus  input, and integrates visual orienting information, and orients the body to the pain stimuli.


The inferior cerebellar peduncle integrates proprioceptive info and outputs to the vestibulocerebellum. 


The thalamus  rings pain to perception and aids in pain suppression and modulation: it allows certain intensities through to the cerebrum and rejecting others.


The somatosensory cortex decodes nociceptors to determine the exact location of pain and is where proprioception is brought into consciousness; 


The Insula judges the intensity of the pain and provides the ability to imagine pain.


The cingulate cortex is presumed to be the memory site for pain.


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