The following passage is a paraphrased version of the excerpt:

The ascending somatosensory pathways from the body to the cerebral cortex are responsible for conveying cutaneous information such as pain, temperature, and crude touch. There are two main pathways involved in this transmission: the dorsal column/medial lemniscal pathway and the spinothalamic pathway. Both pathways involve the crossing of the second-order neuron, allowing sensory information from one side of the body to be transmitted to the opposite side of the brain. The trigeminal nucleus is responsible for homologous central pathways for the head. The cerebellum receives tactile and proprioceptive information from the upper and lower parts of the body through major spinocerebellar pathways. These pathways originating from the head are not shown for clarity. The enteroceptive division of somatosensory pathways has receptors for monitoring the internal state of the body and includes mechanoreceptors that detect gut distention and bladder fullness. The somatosensory pathways can be further classified into two functional categories: fine discriminatory touch sensations and pain/temperature sensations. Fine discriminatory touch sensations include light touch, pressure, vibration, flutter, and stretch/tension. Pain and temperature sensations include both noxious and innocuous cold and warm sensations, as well as mechanical and chemical pain. Itch is closely related to pain and is carried by specific fibers associated with the pain system. Studies on humans using microneurography, a technique involving the insertion of a fine metal microelectrode into a nerve trunk, have allowed for the examination of various cutaneous sensory receptors. This technique has revealed that most of the sensory receptors found in experimental animals are also present in humans. Once the receptive field of a sensory axon is characterized, the same sensory axon can be stimulated using the electrode. In these experiments, the subject is asked to locate the perceived receptive field, which is found to be identical to the mapped receptive field.
Pain, temperature, crude touch 7 • Fig. 7.1 Ascending somatosensory pathways from the body. A, First-, second-, and third-order neurons are shown for the two main pathways conveying cutaneous information from the body to the cerebral cortex: the dorsal column/medial lemniscal and the spinothalamic pathways. Note that the axon of the second-order neuron crosses the midline in both cases, so sensory information from one side of the body is transmitted to the opposite side of the brain, but the levels in the neuraxis at which this takes place are distinct for each pathway. Homologous central pathways for the head originate in the trigeminal nucleus and are described in text, but they are not illustrated for clarity. B, Major spinocerebellar pathways carrying tactile and proprioceptive information to the cerebellum from the upper and lower parts of the body. Again, pathways from the head originate in the trigeminal nuclei but are not shown for clarity. A midsagittal view of the nervous system shows the levels of the spinal and brainstem cross sections in panels A and B.
with them and that underlie conscious and unconscious proprioceptive functions will be covered in this chapter. However, because these receptors also initiate pathways that are intimately involved in the control of movement, they will be discussed again in . Finally, the enteroceptive division has receptors for monitoring the internal state of the body and includes mechanoreceptors that detect distention of the gut or fullness of the bladder. Aspects of enteroceptive division are also covered in as they are related to autonomic functions.
The somatosensory pathways can also be classified by the type of information they carry. Two broad functional categories are recognized, each of which subsumes several somatosensory submodalities. Fine discriminatory touch sensations include light touch, pressure, vibration, flutter (low-frequency vibration), and stretch or tension. The second major functional group of sensations is that of pain and temperature. Submodalities here include both noxious and innocuous cold and warm sensations and mechanical and chemical pain. Itch is also closely related to pain and appears to be carried by particular fibers associated with the pain system.
Thesensoryfunctionsofvariouscutaneoussensoryreceptorshavebeenstudiedinhumansubjectswithatechniqueknownasmicroneurography, inwhichafinemetalmicroelectrodeisinsertedintoanervetrunkinthearmorlegtorecordtheactionpotentialsfromsinglesensoryaxons.Whenarecordingcanbemadefromasinglesensoryaxon,thereceptivefieldofthefiberismapped.Mostofthevarioustypesofsensoryreceptorsthathavebeenstudiedinexperimentalanimalshavealsobeenfoundinhumanswiththistechnique.
Afterthereceptivefieldofasensoryaxonhasbeencharacterized,theelectrodecanbeusedtostimulatethesamesensoryaxon.Intheseexperimentsthesubjectisaskedtolocatetheperceivedreceptivefieldofthesensoryaxon,whichturnsouttobeidenticaltothemappedreceptivefield.