Editing Grey columns

{{short description|Three columns of grey matter within the spinal cord}}
{{distinguish|text=the historic [[Grey Columns]] building in [[Tuskegee, Alabama]]}}

{{Infobox anatomy
| Name        = Grey columns
| Latin       = columnae griseae
| Image       = Medulla spinalis - Section - English.svg
| Caption     = Cross section of the spinal cord. The three grey columns make up the butterfly-shaped shaded region
| Image2      =
| Caption2    =
| Width       = 310
| System      =
| Precursor   =
}}

The '''grey columns'''  are three regions of the somewhat ridge-shaped mass of [[grey matter]] in the [[spinal cord]].<ref>{{citation |title=Gray's anatomy |page=255 
|author1=Henry Gray |author2=Susan Standring |author3=Harold Ellis |author4=B. K. B. Berkovitz |year=2005}}</ref> These regions present as three columns: the [[anterior grey column]], the [[posterior grey column]], and the [[lateral grey column]], all of which are visible in cross-section of the spinal cord. 

The anterior grey column is made up of [[alpha motor neuron]]s, [[gamma motor neuron]]s, and small neurons thought to be [[interneuron]]s.<ref name="Terao">{{cite journal|vauthors=Terao S, Sobue G, Hashizume Y, Li M, Inagaki T, Mitsuma T |title=Age-related changes in human spinal ventral horn cells with special reference to the loss of small neurons in the intermediate zone: a quantitative analysis|journal=Acta Neuropathologica|date=Aug 1996|volume=92|issue=2|pmid=8841655|pages=109–14|doi=10.1007/s004010050497|s2cid=19467756}}</ref> It affects the [[Skeletal muscle|skeletal muscles]].

The posterior grey column receives several types of sensory information regarding touch and sensation from receptors in the skin, bones, and joints, including [[Somatosensory system#fine touch|fine touch]], [[proprioception]], and [[Oscillation|vibration]].{{Citation needed|date=October 2024}} It contains the cell bodies of [[Second-order neuron|second-order sensory neurons]] and their synapses with the [[Pseudounipolar neuron|pseudounipolar]] [[First-order neuron|first-order sensory neurons]] (whose cell bodies are located within the [[Sensory ganglia|sensory ganglia (a.k.a. dorsal root ganglia)]]).

The lateral grey column is only present in the thoracic region and upper lumbar segments (T1-L2). It contains [[preganglionic cell body|preganglionic cell bodies]] of the [[autonomic nervous system]] and sensory relay neurons.

==Structure==

===Anterior grey column===
[[File:Polio spinal diagram-en.svg|thumb|left|The location of [[motor neuron]]s in the anterior grey column of the [[spinal cord]]]]
The '''anterior grey column''', (also known as the anterior horn of spinal cord and anterior cornu) is broad and of a rounded or quadrangular shape. Its posterior part is termed the base, and its anterior part the head, but these are not differentiated from each other by any well-defined constriction. It is separated from the surface of the spinal cord by a layer of white substance which is traversed by the bundles of the anterior nerve roots. In the thoracic region, the posterolateral part of the anterior column projects laterally as a triangular field, which is named the [[lateral grey column]]. It comprises three different types of neurons, two types of [[lower motor neuron]] – large [[alpha motor neurons]], and medium [[gamma motor neurons]], and small neurons thought to be [[interneurons]].<ref name="Terao" /> These neurons differ in both their [[Neuromorphology#General morphology|morphology]] and in their patterns of connectivity.<ref name="Friese">{{cite journal|vauthors=Friese A, Kaltschmidt JA, Ladle DR, Sigrist M, Jessell TM, Arber S|title=Gamma and alpha motor neurons distinguished by expression of transcription factor Err3|journal=Proceedings of the National Academy of Sciences of the United States of America|date=Aug 11, 2009|volume=106|issue=32|pmid=19651609|pmc=2716387|doi=10.1073/pnas.0906809106|pages=13588–13593|bibcode=2009PNAS..10613588F|doi-access=free}}</ref> They are organized in the same manner as the muscles they innervate.<ref name="Siegel" />

====Alpha motor neurons====
Alpha motor neurons are [[lower motor neuron]]s that innervate [[extrafusal muscle fibers]] to generate force at [[neuromuscular junctions]] at the start of a [[muscle contraction]]. They have large cell bodies and receive [[proprioception|proprioceptive]] input.<ref name="Friese" /> They have been shown to reduce in population, but not in size with age.<ref name="Terao" /> Damage to these cell bodies can lead to severe muscle weakness and loss of reflexes, and is also associated with [[ALS]].<ref name="Haines">{{cite book|last=Haines|first=Duane|title=Fundamental Neuroscience for Basic and Clinical Applications|year=2012|publisher=Saunders|page=138|isbn=978-1437702941}}</ref><ref name="JoN">{{cite journal |last1=Van Den Berg-Vos |first1=RM |last2=Van Den Berg |first2=LH |last3=Visser |first3=J |last4=de Visser |first4=M |last5=Franssen |first5=H |last6=Wokke |first6=JH |title=The spectrum of lower motor neuron syndromes. |journal=Journal of Neurology |date=November 2003 |volume=250 |issue=11 |pages=1279–92 |doi=10.1007/s00415-003-0235-9 |pmid=14648143}}</ref>

====Gamma motor neurons====
Gamma motor neurons innervate [[intrafusal muscle fibers]] that control the sensitivity of [[muscle spindles]] to stretch. They have smaller cell bodies than alpha motor neurons and do not receive proprioceptive input.<ref name="Friese" /> They have been shown to reduce in numbers but not size with age.<ref name="Terao" />

====Small neurons====
The physiology of the small neurons in the anterior column is not well understood. Their effects can be both [[Excitatory postsynaptic potential|excitatory]] and [[Inhibitory postsynaptic potential|inhibitory]]. They are suspected to be interneurons and have been shown to reduce in size but not numbers with age.<ref name="Terao" />

'''Clinical significance'''

It is these cells that are affected in the following diseases,{{Citation needed|date=October 2024}} – [[amyotrophic lateral sclerosis]], [[spinal and bulbar muscular atrophy]], [[Charcot–Marie–Tooth disease]], [[progressive muscular atrophy]], all [[spinal muscular atrophies]], [[poliomyelitis]], and [[West Nile virus]].

'''Pharmacological interaction'''

The anterior grey column is the target for some [[Antispasmodic|spasmolytic]] medications. [[Norepinephrine]] release here, (as induced by [[cyclobenzaprine]]) reduces spasms by innervation (reducing nerve activity) of [[alpha motor neurons]] via interaction with [[Gamma motor neurons|gamma fibers]].<ref>{{cite web|title=Cyclobenzaprine|website=[[DrugBank]]|url=http://www.drugbank.ca/drugs/DB00924}}</ref>
===Posterior grey column===
[[File: Gray675.png|thumb|left|240px|Spinal nerve forming from grey column]]The '''posterior grey column''', also known as the posterior (or dorsal) horn of spinal cord, is subdivided into six layers known as [[Rexed laminae]], based on the type of sensory information sent to each section.<ref name="Cagle">{{cite journal |last=Cagle |first=MC |author2=Honig, MG |date=July 2013 |title=Parcellation of Cblns 1, 2, and 4 among different subpopulations of dorsal horn neurons in mouse spinal cord. |journal=Journal of Comparative Neurology |volume=522 |issue=2 |pages=479–97 |doi=10.1002/cne.23422 |pmc=3855892 |pmid=23853053}}</ref> 

* [[Marginal nucleus of spinal cord]] (lamina I)
* [[Substantia gelatinosa of Rolando]] (lamina II)
* [[Nucleus proprius]] (laminae III, IV)
* [[Spinal lamina V]], the neck of the posterior horn <ref name="isbn1-888799-61-7">{{cite book |author1=Woolsey, Robert M. |author2=Vernon W. Lin |author3=Cardenas, Diana D. |author4=Cutter, Nancy C. |author5=Frederick S. Frost |author6=Margaret C. Hammond |author7=Laurie B. Lindblom |author8=Inder Perkash |author9=Robert Waters |title=Spinal Cord Medicine: Principles and Practice |publisher=Demos Medical Publishing |year=2002 |isbn=1-888799-61-7 }}</ref>
* [[Spinal lamina VI]], the base of the posterior horn.

The other four laminae are located in the other two grey columns in the spinal cord.

The function of the spinal dorsal horn is to process and integrate sensory information from the [[peripheral nervous system]]. It receives inputs from [[Type Ia sensory fiber|primary afferent fibers]] and modulatory systems, and it projects to higher brain centers and [[Motor neuron|motor neurons]]. The dorsal horn circuitry is involved in various aspects of sensory processing, including discrimination, integration, and modulation of [[Pain|nociceptive]] and non-nociceptive signals. Dysfunction of the dorsal horn circuitry has been implicated in chronic pain conditions and other neurological disorders.<ref>{{Cite journal |last1=Harding |first1=Erika K. |last2=Fung |first2=Samuel Wanchi |last3=Bonin |first3=Robert P. |date=2020 |title=Insights Into Spinal Dorsal Horn Circuit Function and Dysfunction Using Optical Approaches |journal=Frontiers in Neural Circuits |volume=14 |page=31 |doi=10.3389/fncir.2020.00031 |doi-access=free |issn=1662-5110 |pmc=7303281 |pmid=32595458}}</ref>

Laminae I and II receive information from [[afferent neurons]] that sense nociception, temperature, and itching, laminae III and IV are sent information from neurons that sense mechanical pressure, and laminae V and VI are sent information from proprioceptors.<ref name="Brown">{{cite book|last=Brown|first=AG|title=Organization in the Spinal Cord: The Anatomy and Physiology of Identified Neurones|year=1981|publisher=Springer-Verlag|location=Berlin}}</ref> It is known to be the primary relay point for [[Haptic perception|haptic]] and [[Nociception|nociceptive]] messages.<ref name="Gauriau" /> The posterior horn is also known as a partially layered structure because only laminae I and II are well defined.

The column can also be separated by nociceptive and non-nociceptive senses. Laminae I and II are important in nociception, laminae III and IV are not involved nociception, and lamina V is involved in both nociception and non-nociception.<ref name="Kato org">{{cite journal|vauthors=Kato G, Kawasaki Y, Koga K, Uta D, Kosugi M, Yasaka T, Yoshimura M, Ji RR, Strassman AM |title=Organization of intralaminar and translaminar neuronal connectivity in the superficial spinal dorsal horn|journal=The Journal of Neuroscience|date=April 2009|volume=29|issue=16|pmid=19386904|pmc=2777732|doi=10.1523/JNEUROSCI.6175-08.2009|pages=5088–5099}}</ref>

The function of the spinal dorsal horn is to process and integrate sensory information from the [[peripheral nervous system]]. It receives inputs from [[Type Ia sensory fiber|primary afferent fibers]] and modulatory systems, and it projects to higher brain centers and [[Motor neuron|motor neurons]]. The dorsal horn circuitry is involved in various aspects of sensory processing, including discrimination, integration, and modulation of [[Pain|nociceptive]] and non-nociceptive signals. Dysfunction of the dorsal horn circuitry has been implicated in chronic pain conditions and other neurological disorders. 
[[File:Medulla spinalis - Substantia grisea - English.svg|thumb|Laminae]]

====Lamina I====
Lamina I is also known as the [[marginal nucleus of spinal cord]]. The majority of posterior column projection neurons are located in lamina I, however most neurons in this layer are interneurons.<ref name="todd rev">{{cite journal|last=Todd|first=Andrew|title=Neuronal circuitry for pain processing in the dorsal horn|journal=Nature Reviews Neuroscience|date=Dec 2010|volume=11|issue=12|pmid=21068766|pmc=3277941|doi=10.1038/nrn2947|pages=823–836}}</ref>  The main areas these neurons innervate are the [[caudal ventrolateral medulla]] (CVLM), the [[nucleus of the solitary tract]] (NTS), the [[Lateral parabrachial nucleus|lateral parabrachial area]] (LPb), the [[periaqueductal grey matter]] (PAG), and certain regions in the [[thalamus]].<ref name="Gauriau">{{cite journal|last=Gauriau|first=Caroline|author2=Bernard, Jean-François|title=A comparative reappraisal of projections from the superficial laminae of the dorsal horn in the rat: The forebrain|journal=The Journal of Comparative Neurology|year=2004|volume=468|issue=1|pmid=14648689|doi=10.1002/cne.10873|pages=24–56|s2cid=26117604}}</ref> The CVLM receives nociceptive and [[cardiovascular]] responses.<ref name="Lima">{{cite journal|vauthors=Lima D, Albino-Teixeira A, Tavares I |title=The caudal medullary ventrolateral reticular formation in nociceptive-cardiovascular integration. An experimental study in the rat|journal=Experimental Physiology|date=Mar 2002|volume=87|issue=2|pmid=11856973|pages=267–74|doi=10.1113/eph8702354|s2cid=13605412|doi-access=free}}</ref>  The NTS receives cardio-respiratory inputs and affects [[reflex tachycardia]] from noxious stimulation.<ref name="Boscan">{{cite journal|vauthors=Boscan P, Pickering AE, Paton JF |title=The nucleus of the solitary tract: an integrating station for nociceptive and cardiorespiratory afferents|journal=Experimental Physiology|date=Mar 2002|volume=87|issue=2|pmid=11856972|pages=259–66|doi=10.1113/eph8702353|s2cid=22373004|doi-access=free}}</ref>  The LPb projects to the [[amygdala]] and [[hypothalamus]] and is involved in the emotional response to pain.<ref name="gauriau LPb">{{cite journal|last=Gauriau|first=C|author2=Bernard, J. F.|title=Pain pathways and parabrachial circuits in the rat|journal=Experimental Physiology|date=Mar 2002|volume=87|issue=2|pmid=11856971|pages=251–8|doi=10.1113/eph8702357|s2cid=42574814|doi-access=free}}</ref>  The PAG develops ways to deal with pain and is a main target of [[analgesics]]. It projects to other parts of the brainstem.<ref name="Heinricher">{{cite journal|vauthors=Heinricher MM, Tavares I, Leith JL, Lumb BM |title=Descending control of nociception: Specificity, recruitment and plasticity|journal=Brain Research Reviews|date=Apr 2009|volume=60|issue=1|pmid=19146877|pmc=2894733|doi=10.1016/j.brainresrev.2008.12.009|pages=214–225}}</ref>  The nuclei of the thalamus affect sensory and motivational aspects of pain.<ref name="Gauriau thalamus">{{cite journal|last=Gauriau|first=C.|author2=Bernard, J. F.|journal=Journal of Neuroscience|title=Posterior triangular thalamic neurons convey nociceptive messages to the secondary somatosensory and insular cortices in the rat|date=Jan 2004|volume=24|issue=3|pmid=14736861|doi=10.1523/JNEUROSCI.3272-03.2004|pages=752–61|pmc=6729251|doi-access=free}}</ref> The neurons of this lamina can be distinguished by their morphology as [[pyramidal neuron|pyramidal]], [[spindle neuron|spindle]], or [[multipolar neuron|multipolar]].<ref name="Han">{{cite journal|vauthors=Han ZS, Zhang ET, Craig AD |title=Nociceptive and thermoreceptive lamina I neurons are anatomically distinct|journal=Nature Neuroscience|date=Jul 1998|volume=1|issue=3|pmid=10195146|doi=10.1038/665|pages=218–25|s2cid=21222047}}</ref>

====Lamina II====
This layer is also known as the [[substantia gelatinosa of Rolando]] and has the highest density of neurons.<ref name="Paxinos">{{cite book|last=Paxinos|first=George|title=The Human Nervous System|year=2004|publisher=Academic Press|isbn=978-0125476263}}</ref>  These neurons mediate the activity of nociceptive and temperature afferent fibers.<ref name="Siegel" />  It is almost entirely made up of interneurons which can be further divided by their morphology. The four main morphological classes, based on the shape of their dendritic structure, are islet, central, vertical, and radial cells. The interneurons can also be divided by their function: excitatory or inhibitory. The excitatory interneurons release [[glutamate]] as their main [[neurotransmitter]] and the inhibitory interneurons use [[GABA]] and/or [[glycine]] as their main neurotransmitter. The neurons of this layer are only [[C fibers]] and contain almost no [[myelin]].<ref name="grudt">{{cite journal|last=Grudt|first=T. J.|author2=Perl, E. R.|title=Correlations between neuronal morphology and electrophysiological features in the rodent superficial dorsal horn|journal=The Journal of Physiology|date=Apr 1, 2002|volume=540|issue=Pt 1|pmid=11927679|pmc=2290200|pages=189–207|doi=10.1113/jphysiol.2001.012890}}</ref>

====Laminae III and IV====
These laminae are also known as the [[nucleus proprius]] and contain a much smaller density of neurons than lamina II.<ref name="Paxinos" />  There are projection neurons scattered throughout these layers.<ref name="todd rev" /> Mechanosensitive [[A beta fibers]] terminate in these layers.<ref name="Kato org" /> The layers receive input from lamina II and also control pain, temperature, and crude touch.<ref name="Siegel" />  C fibers that control nociception and temperature and sensory information from mechanoreceptors are relayed here.<ref name="Muthayya">{{cite book|last=Muthayya|first=NM|title=Human Physiology|year=2002|publisher=Jaypee Brothers Medical Publishers|location=New Delhi}}</ref>

====Lamina V====
This lamina is also known as the neck of the posterior column and receives information from mechanoreceptors and danger information from nociceptors.<ref name="Muthayya" /> It has different neurons in different regions. In the medial region it contains medium-sized triangular neurons and the lateral region contains medium-sized multipolar neurons.<ref name="Paxinos" />

====Lamina VI====
This lamina is only found in the [[Cervical vertebrae|cervical]] and [[lumbar]] regions of the spinal cord. It receives afferent input from muscle fibers and joints.<ref name="Siegel">{{cite book|last=Siegel|first=Allan|title=Essential Neuroscience|url=https://archive.org/details/essentialneurosc0000sieg_c0n4|url-access=registration|year=2010|publisher=Lippincott Williams & Wilkins|isbn=978-0781783835}}</ref>

===Lateral grey column===
The '''lateral grey column''', or the lateral horn of spinal cord, is part of the [[sympathetic nervous system]] and receives input from [[brain stem]], organs, and [[hypothalamus]]. The lateral column is only present in the thoracic region and upper lumbar segments. The lateral grey column contains preganglionic cell bodies of the autonomic nervous system and sensory relay neurons.

==Clinical significance==
Neurons in the anterior column have been shown to be affected by [[amyotrophic lateral sclerosis]] (ALS). The number of large alpha motor neurons and medium gamma motor neurons was greatly reduced and the number of small neurons was either slightly or greatly reduced depending on the type of ALS.<ref name="Terao ALS">{{cite journal|vauthors=Terao S, Sobue G, Hashizume Y, Mitsuma T, Takahashi A |title=Disease-specific patterns of neuronal loss in the spinal ventral horn in amyotrophic lateral sclerosis, multiple system atrophy and X-linked recessive bulbospinal neuronopathy, with special reference to the loss of small neurons in the intermediate zone|journal=Journal of Neurology|date=Feb 1994|volume=241|issue=4|pmid=8195817|pages=196–203|doi=10.1007/bf00863768|s2cid=23011881}}</ref>[[File: Gray664.png|thumb|Cross-sectional view of spinal cord]]

[[Muscular atrophy]] has also been shown to have an effect on neurons of the anterior column. A large loss of large alpha motor neurons, medium gamma motor neurons, and small neurons was recorded in cases of muscular atrophy.<ref name="Terao atrophy">{{cite journal|vauthors=Terao S, Sobue G, Li M, Hashizume Y, Tanaka F, Mitsuma T |title=The lateral corticospinal tract and spinal ventral horn in X-linked recessive spinal and bulbar muscular atrophy: a quantitative study|journal=Acta Neuropathologica|date=Jan 1997|volume=93|issue=1|pmid=9006650|pages=1–6|doi=10.1007/s004010050575|s2cid=12023369}}</ref>

Damage to the '''lateral column''' can result in [[Horner's syndrome]].

[[Multiple system atrophy]] (MSA), has also been linked to the lateral grey column. MSA has been shown to reduce the cell count in the lateral column by over 50%.

The '''posterior column''' has a prominent role in the '''pain system''', it is the first central relay in the nociceptive pathway. The [[First-order neuron|first-order afferent neuron]] carries sensory information to the second order neuron in the dorsal horn. The axon of the second order neuron, if it is a projection neuron and not an interneuron, then goes to the third order neuron in the [[thalamus]]. The thalamus is known as the "gateway to the cortex". The third order neuron then goes to the [[cerebral cortex]]. The afferent neurons are either A fibers or C fibers. A fibers are myelinated allowing for faster signal conduction. Among these there are A beta fibers which are faster and carry information about non-painful touch and [[A delta fiber]]s which are slower and thinner than the A beta fibers. The C fibers are not myelinated and therefore slower.<ref name="todd rev" /> C fibers that carry nociceptive signals can be divided into two types: fibers that contain [[neuropeptides]], like [[substance P]], and fibers that do not contain neuropeptides.<ref name=Snider>{{cite journal|last=Snider|first=W. D.|author2=McMahon, S. B.|title=Tackling pain at the source: new ideas about nociceptors|journal=Neuron|date=Apr 1998|volume=20|issue=4|pmid=9581756|pages=629–32|doi=10.1016/s0896-6273(00)81003-x|s2cid=18001663|doi-access=free}}</ref> The two types terminate in very different areas. Non-peptidergic C fibers are linked to the skin, where they innervate the [[epidermis (skin)|epidermis]] while peptidergic C fibers innervate other tissues and deeper parts of the skin.<ref name="todd rev" />

There are two main types of nociceptive signals: sensory and affective.

===Sensory===

Sensory nociceptive signals provide information about what kind of stimulus (heat, mechanical, etc.) is affecting the body and also indicates where on the body the stimulus is. Sensory nociceptive neurons have a small [[receptive field]] to help pinpoint the exact location of a stimulus.<ref name=price>{{cite journal|last=Price|first=Donald|title=Central neural mechanisms that interrelate sensory and affective dimensions of pain|journal=Molecular Interventions|date=Oct 2002|volume=2|issue=6|pmid=14993415|doi=10.1124/mi.2.6.392|pages=392–403, 339}}</ref>

===Affective===

Affective nociceptive signals affect emotions. These signals go to the [[limbic system]] and tell the body to react to the danger stimulus (i.e. removing a hand from a hot stove). These neurons have larger receptive fields because the emotional reaction to most pain stimuli is similar.<ref name=price/>

==See also==
* [[Beta motor neuron]]
* [[Gamma motor neuron]]
* [[Posterior column-medial lemniscus pathway]]
* [[Posterior horn of lateral ventricles]]
* [[Type Ia sensory fiber]]


==References==
{{Gray's}}
{{Reflist|30em}}

{{Spinal cord}}
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[[Category:Spinal cord]]