<P> The dorsal root ganglia develop in the embryo from neural crest cells, not neural tube . Hence, the spinal ganglia can be regarded as gray matter of the spinal cord that became translocated to the periphery . </P> <P> Proton - sensing G protein - coupled receptors are expressed by DRG sensory neurons and might play a role in acid - induced nociception . </P> <P> The nerve endings of dorsal root ganglion neurons have a variety of sensory receptors that are activated by mechanical, thermal, chemical, and noxious stimuli . In these sensory neurons, a group of ion channels thought to be responsible for somatosensory transduction have been identified . Compression of the dorsal root ganglion by a mechanical stimulus lowers the voltage threshold needed to evoke a response and causes action potentials to be fired . This firing may even persist after the removal of the stimulus . </P> <P> Two distinct types of mechanosensitive ion channels have been found in the posterior root ganglion neurons . The two channels are broadly classified as either high - threshold (HT) or low threshold (LT). As their names suggest, they have different thresholds as well as different sensitivities to pressure . These are cationic channels whose activity appears to be regulated by the proper functioning of the cytoskeleton and cytoskeleton associated proteins . The presence of these channels in the posterior root ganglion gives reason to believe that other sensory neurons may contain them as well . </P>

Where do the sensory neuron fibers enter the spinal cord