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63-515: The Rexed laminae (singular: Rexed lamina) comprise a system of ten layers of grey matter (I–X), identified in the early 1950s by Bror Rexed to label portions of the grey columns of the spinal cord . Similar to Brodmann areas , they are defined by their cellular structure rather than by their location, but the location still remains reasonably consistent. Grey matter Grey matter , or brain matter in American English ,

126-413: A human spinal cord: In the fetus, vertebral segments correspond with spinal cord segments. However, because the vertebral column grows longer than the spinal cord, spinal cord segments do not correspond to vertebral segments in the adult, particularly in the lower spinal cord. For example, lumbar and sacral spinal cord segments are found between vertebral levels T9 and L2, and the spinal cord ends around

189-539: A loss of muscle tone due to disuse of the muscles below the injured site. The two areas of the spinal cord most commonly injured are the cervical spine (C1–C7) and the lumbar spine (L1–L5). (The notation C1, C7, L1, L5 refer to the location of a specific vertebra in either the cervical, thoracic, or lumbar region of the spine.) Spinal cord injury can also be non-traumatic and caused by disease ( transverse myelitis , polio , spina bifida , Friedreich's ataxia , spinal cord tumor , spinal stenosis etc.) Globally, it

252-533: A victim might only suffer loss of hand or foot function. More severe injuries may result in paraplegia , tetraplegia (also known as quadriplegia), or full body paralysis below the site of injury to the spinal cord. Damage to upper motor neuron axons in the spinal cord results in a characteristic pattern of ipsilateral deficits. These include hyperreflexia , hypertonia and muscle weakness. Lower motor neuronal damage results in its own characteristic pattern of deficits. Rather than an entire side of deficits, there

315-414: Is a major component of the central nervous system , consisting of neuronal cell bodies , neuropil ( dendrites and unmyelinated axons ), glial cells ( astrocytes and oligodendrocytes ), synapses , and capillaries . Grey matter is distinguished from white matter in that it contains numerous cell bodies and relatively few myelinated axons, while white matter contains relatively few cell bodies and

378-430: Is a pattern relating to the myotome affected by the damage. Additionally, lower motor neurons are characterized by muscle weakness, hypotonia , hyporeflexia and muscle atrophy . Spinal shock and neurogenic shock can occur from a spinal injury. Spinal shock is usually temporary, lasting only for 24–48 hours, and is a temporary absence of sensory and motor functions. Neurogenic shock lasts for weeks and can lead to

441-412: Is also the location of groups of spinal interneurons that make up the neural circuits known as central pattern generators . These circuits are responsible for controlling motor instructions for rhythmic movements such as walking. A congenital disorder is diastematomyelia in which part of the spinal cord is split usually at the level of the upper lumbar vertebrae. Sometimes the split can be along

504-413: Is around 45 cm (18 in) long in adult men and around 43 cm (17 in) long in adult women. The diameter of the spinal cord ranges from 13 mm ( 1 ⁄ 2  in) in the cervical and lumbar regions to 6.4 mm ( 1 ⁄ 4  in) in the thoracic area. The spinal cord functions primarily in the transmission of nerve signals from the motor cortex to the body, and from

567-745: Is comparable to that taking place during adolescence, a hormonally similar transitional period of life. In the current edition of the official Latin nomenclature, Terminologia Anatomica , substantia grisea is used for English grey matter . The adjective grisea for grey is however not attested in classical Latin . The adjective grisea is derived from the French word for grey, gris . Alternative designations like substantia cana and substantia cinerea are being used alternatively. The adjective cana , attested in classical Latin, can mean grey , or greyish white . The classical Latin cinerea means ash-coloured . Spinal cord In humans ,

630-400: Is composed chiefly of long-range myelinated axons. The colour difference arises mainly from the whiteness of myelin . In living tissue, grey matter actually has a very light grey colour with yellowish or pinkish hues, which come from capillary blood vessels and neuronal cell bodies. Grey matter refers to unmyelinated neurons and other cells of the central nervous system . It is present in

693-454: Is enlarged in the cervical and lumbar regions. The cervical enlargement, stretching from the C4 to T1 vertebrae, is where sensory input comes from and motor output goes to the arms and trunk. The lumbar enlargement, located between T10 and L1, handles sensory input and motor output coming from and going to the legs. The spinal cord is continuous with the caudal portion of the medulla , running from

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756-533: Is expected there are around 40 to 80 cases of spinal cord injury per million population, and approximately 90% of these cases result from traumatic events. Real or suspected spinal cord injuries need immediate immobilisation including that of the head. Scans will be needed to assess the injury. A steroid, methylprednisolone , can be of help as can physical therapy and possibly antioxidants . Treatments need to focus on limiting post-injury cell death, promoting cell regeneration, and replacing lost cells. Regeneration

819-477: Is inadequate to maintain the spinal cord beyond the cervical segments. The major contribution to the arterial blood supply of the spinal cord below the cervical region comes from the radially arranged posterior and anterior radicular arteries , which run into the spinal cord alongside the dorsal and ventral nerve roots, but with one exception do not connect directly with any of the three longitudinal arteries. These intercostal and lumbar radicular arteries arise from

882-405: Is known as the cuneocerebellar tract . The descending tracts are of motor information. Descending tracts involve two neurons: the upper motor neuron, and lower motor neuron. A nerve signal travels down the upper motor neuron until it synapses with the lower motor neuron in the spinal cord. Then, the lower motor neuron conducts the nerve signal to the spinal root where efferent nerve fibers carry

945-431: Is necessary for the correct assembly of the nervous system. Overall, spontaneous embryonic activity has been shown to play a role in neuron and muscle development but is probably not involved in the initial formation of connections between spinal neurons. The spinal cord mainly functions to carry information to and from the brain, in ascending and descending tracts. There are two ascending somatosensory pathways in

1008-528: Is not correlated with changes in white or grey matter. However, several cross-sectional studies have shown that repeated long-term cannabis use is associated with smaller grey matter volumes in the hippocampus , amygdala , medial temporal cortex , and prefrontal cortex , with increased grey matter volume in the cerebellum. Long-term cannabis use is also associated with alterations in white matter integrity in an age-dependent manner, with heavy cannabis use during adolescence and early adulthood associated with

1071-537: Is the groove in the ventral side. The human spinal cord is divided into segments where pairs of spinal nerves (mixed; sensory and motor) form. Six to eight motor nerve rootlets branch out of right and left ventralateral sulci in a very orderly manner. Nerve rootlets combine to form nerve roots. Likewise, sensory nerve rootlets form off right and left dorsal lateral sulci and form sensory nerve roots. The ventral (motor) and dorsal (sensory) roots combine to form spinal nerves (mixed; motor and sensory), one on each side of

1134-504: Is the main pathway for information connecting the brain and peripheral nervous system . Much shorter than its protecting spinal column, the human spinal cord originates in the brainstem, passes through the foramen magnum , and continues through to the conus medullaris near the second lumbar vertebra before terminating in a fibrous extension known as the filum terminale . It is about 45 centimetres (18 inches) long in males and about 43 cm (17 in) in females, ovoid -shaped, and

1197-453: The afferent fibers of the sensory neurons to the sensory cortex . It is also a center for coordinating many reflexes and contains reflex arcs that can independently control reflexes. It is also the location of groups of spinal interneurons that make up the neural circuits known as central pattern generators . These circuits are responsible for controlling motor instructions for rhythmic movements such as walking. The spinal cord

1260-454: The brain , brainstem and cerebellum , and present throughout the spinal cord . Grey matter is distributed at the surface of the cerebral hemispheres ( cerebral cortex ) and of the cerebellum ( cerebellar cortex ), as well as in the depths of the cerebrum (the thalamus ; hypothalamus ; subthalamus , basal ganglia – putamen , globus pallidus and nucleus accumbens ; as well as the septal nuclei ), cerebellum (deep cerebellar nuclei –

1323-416: The dentate nuclei , globose nucleus , emboliform nucleus , and fastigial nucleus ), and brainstem (the substantia nigra , red nucleus , olivary nuclei , and cranial nerve nuclei ). Grey matter in the spinal cord is known as the grey column which travels down the spinal cord distributed in three grey columns that are presented in an "H" shape. The forward-facing column is the anterior grey column ,

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1386-409: The spinal cord is split into three grey columns: The grey matter of the spinal cord can be divided into different layers, called Rexed laminae . These describe, in general, the purpose of the cells within the grey matter of the spinal cord at a particular location. High alcohol consumption has been correlated with significant reductions in grey matter volume. Short-term cannabis use (30 days)

1449-466: The superior cerebellar peduncle where they decussate again. From here, the information is brought to deep nuclei of the cerebellum including the fastigial and interposed nuclei . From the levels of L2 to T1, proprioceptive information enters the spinal cord and ascends ipsilaterally, where it synapses in Clarke's nucleus . The secondary neuronal axons continue to ascend ipsilaterally and then pass into

1512-603: The vestibulospinal tract , the tectospinal tract and the reticulospinal tract . The rubrospinal tract descends with the lateral corticospinal tract, and the remaining three descend with the anterior corticospinal tract. The function of lower motor neurons can be divided into two different groups: the lateral corticospinal tract and the anterior cortical spinal tract. The lateral tract contains upper motor neuronal axons which synapse on dorsal lateral (DL) lower motor neurons. The DL neurons are involved in distal limb control. Therefore, these DL neurons are found specifically only in

1575-502: The L1/L2 vertebral level, forming a structure known as the conus medullaris. Although the spinal cord cell bodies end around the L1/L2 vertebral level, the spinal nerves for each segment exit at the level of the corresponding vertebra. For the nerves of the lower spinal cord, this means that they exit the vertebral column much lower (more caudally) than their roots. As these nerves travel from their respective roots to their point of exit from

1638-556: The T11 spinal segment is located higher than the T11 bony vertebra, and the sacral spinal cord segment is higher than the L1 vertebral body. The grey columns , (three regions of grey matter) in the center of the cord, is shaped like a butterfly and consists of cell bodies of interneurons , motor neurons, neuroglia cells and unmyelinated axons. The anterior and posterior grey columns present as projections of grey matter and are also known as

1701-526: The age of 8 the volume of grey matter begins to decrease. However, the density of grey matter appears to increase as a child develops into early adulthood. Males tend to exhibit grey matter of increased volume but lower density than that of females. Grey matter contains most of the brain's neuronal cell bodies. The grey matter includes regions of the brain involved in muscle control, and sensory perception such as seeing and hearing, memory, emotions, speech, decision-making, and self-control. The grey matter in

1764-537: The anterior column but do not synapse across the anterior white commissure. Rather, they only synapse on VM lower motor neurons ipsilaterally. The VM lower motor neurons control the large, postural muscles of the axial skeleton . These lower motor neurons, unlike those of the DL, are located in the ventral horn all the way throughout the spinal cord. The spinal cord is a center for coordinating many reflexes and contains reflex arcs that can independently control reflexes. It

1827-400: The aorta for example during aortic aneurysm repair, can result in spinal cord infarction and paraplegia. The spinal cord is made from part of the neural tube during development. There are four stages of the spinal cord that arises from the neural tube: The neural plate, neural fold, neural tube, and the spinal cord. Neural differentiation occurs within the spinal cord portion of the tube. As

1890-461: The aorta, provide major anastomoses and supplement the blood flow to the spinal cord. In humans the largest of the anterior radicular arteries is known as the artery of Adamkiewicz , or anterior radicularis magna (ARM) artery, which usually arises between L1 and L2, but can arise anywhere from T9 to L5. Impaired blood flow through these critical radicular arteries, especially during surgical procedures that involve abrupt disruption of blood flow through

1953-430: The arachnoid and the underlying pia mater is called the subarachnoid space . The subarachnoid space contains cerebrospinal fluid , which can be sampled with a lumbar puncture , or "spinal tap" procedure. The delicate pia mater, the innermost protective layer, is tightly associated with the surface of the spinal cord. The cord is stabilized within the dura mater by the connecting denticulate ligaments , which extend from

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2016-494: The base of the skull to the body of the first lumbar vertebra. It does not run the full length of the vertebral column in adults. It is made of 31 segments from which branch one pair of sensory nerve roots and one pair of motor nerve roots. The nerve roots then merge into bilaterally symmetrical pairs of spinal nerves . The peripheral nervous system is made up of these spinal roots, nerves, and ganglia . The dorsal roots are afferent fascicles , receiving sensory information from

2079-417: The canal. The dura mater is the outermost layer, and it forms a tough protective coating. Between the dura mater and the surrounding bone of the vertebrae is a space called the epidural space . The epidural space is filled with adipose tissue , and it contains a network of blood vessels . The arachnoid mater , the middle protective layer, is named for its open, spiderweb-like appearance. The space between

2142-423: The cerebellum via the inferior cerebellar peduncle . This tract is known as the dorsal spinocerebellar tract. From above T1, proprioceptive primary axons enter the spinal cord and ascend ipsilaterally until reaching the accessory cuneate nucleus , where they synapse. The secondary axons pass into the cerebellum via the inferior cerebellar peduncle where again, these axons synapse on cerebellar deep nuclei. This tract

2205-564: The cervical and lumbosacral enlargements within the spinal cord. There is no decussation in the lateral corticospinal tract after the decussation at the medullary pyramids. The anterior corticospinal tract descends ipsilaterally in the anterior column, where the axons emerge and either synapse on lower ventromedial (VM) motor neurons in the ventral horn ipsilaterally or descussate at the anterior white commissure where they synapse on VM lower motor neurons contralaterally . The tectospinal, vestibulospinal and reticulospinal descend ipsilaterally in

2268-411: The closure of the caudal neuropore and formation of the brain's ventricles that contain the choroid plexus tissue, the central canal of the caudal spinal cord is filled with cerebrospinal fluid. Earlier findings by Viktor Hamburger and Rita Levi-Montalcini in the chick embryo have been confirmed by more recent studies which have demonstrated that the elimination of neuronal cells by programmed cell death

2331-412: The cortex. Additionally, some ALS axons from the spinomesencephalic pathway project to the periaqueductal gray in the pons, and the axons forming the periaqueductal gray then project to the nucleus raphes magnus , which projects back down to where the pain signal is coming from and inhibits it. This helps control the sensation of pain to some degree. Proprioceptive information in the body travels up

2394-428: The enveloping pia mater laterally between the dorsal and ventral roots. The dural sac ends at the vertebral level of the second sacral vertebra. In cross-section, the peripheral region of the cord contains neuronal white matter tracts containing sensory and motor axons . Internal to this peripheral region is the grey matter , which contains the nerve cell bodies arranged in the three grey columns that give

2457-695: The greatest amount of change. Meditation has been shown to change grey matter structure. Habitual playing of action video games has been reported to promote a reduction of grey matter in the hippocampus while 3D platformer games have been reported to increase grey matter in the hippocampus. Women and men with equivalent IQ scores have differing proportions of grey to white matter in cortical brain regions associated with intelligence. Pregnancy renders substantial changes in brain structure, primarily reductions in grey matter volume in regions subserving social cognition. Grey matter reductions endure for at least 2 years post-pregnancy. The profile of brain changes

2520-423: The horns of the spinal cord. The white matter is located outside of the grey matter and consists almost totally of myelinated motor and sensory axons. Columns of white matter known as funiculi carry information either up or down the spinal cord. The spinal cord proper terminates in a region called the conus medullaris , while the pia mater continues as an extension called the filum terminale , which anchors

2583-417: The ipsilateral side as the ventral corticospinal tract. These axons also synapse with lower motor neurons in the ventral horns. Most of them will cross to the contralateral side of the cord (via the anterior white commissure ) right before synapsing. The midbrain nuclei include four motor tracts that send upper motor neuronal axons down the spinal cord to lower motor neurons. These are the rubrospinal tract ,

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2646-418: The length of the spinal cord. Spinal cord injuries can be caused by trauma to the spinal column (stretching, bruising, applying pressure, severing, laceration, etc.). The vertebral bones or intervertebral disks can shatter, causing the spinal cord to be punctured by a sharp fragment of bone . Usually, victims of spinal cord injuries will suffer loss of feeling in certain parts of their body. In milder cases,

2709-424: The lumen of the neural tube narrows to form the small central canal of the spinal cord. The alar plate and the basal plate are separated by the sulcus limitans. Additionally, the floor plate also secretes netrins . The netrins act as chemoattractants to decussation of pain and temperature sensory neurons in the alar plate across the anterior white commissure, where they then ascend towards the thalamus . Following

2772-428: The medial part of the column. If the axon enters above level T6, then it travels in the cuneate fasciculus , which is lateral to the fasciculus gracilis. Either way, the primary axon ascends to the lower medulla , where it leaves its fasciculus and synapses with a secondary neuron in one of the dorsal column nuclei : either the nucleus gracilis or the nucleus cuneatus , depending on the pathway it took. At this point,

2835-526: The motor signal toward the target muscle. The descending tracts are composed of white matter. There are several descending tracts serving different functions. The corticospinal tracts (lateral and anterior) are responsible for coordinated limb movements. The corticospinal tract serves as the motor pathway for upper motor neuronal signals coming from the cerebral cortex and from primitive brainstem motor nuclei. Cortical upper motor neurons originate from Brodmann areas 1, 2, 3, 4, and 6 and then descend in

2898-465: The neural tube begins to develop, the notochord begins to secrete a factor known as Sonic hedgehog (SHH). As a result, the floor plate then also begins to secrete SHH, and this will induce the basal plate to develop motor neurons . During the maturation of the neural tube, its lateral walls thicken and form a longitudinal groove called the sulcus limitans . This extends the length of the spinal cord into dorsal and ventral portions as well. Meanwhile,

2961-442: The overlying ectoderm secretes bone morphogenetic protein (BMP). This induces the roof plate to begin to secrete BMP, which will induce the alar plate to develop sensory neurons . Opposing gradients of such morphogens as BMP and SHH form different domains of dividing cells along the dorsal ventral axis. Dorsal root ganglion neurons differentiate from neural crest progenitors. As the dorsal and ventral column cells proliferate,

3024-665: The posterior limb of the internal capsule and end in the primary sensory cortex . The proprioception of the lower limbs differs from the upper limbs and upper trunk. There is a four-neuron pathway for lower limb proprioception. This pathway initially follows the dorsal spino-cerebellar pathway. It is arranged as follows: proprioceptive receptors of lower limb → peripheral process → dorsal root ganglion → central process →  Clarke's column  → 2nd order neuron → spinocerebellar tract →cerebellum. The anterolateral system (ALS) works somewhat differently. Its primary neurons axons enter

3087-422: The posterior limb of the internal capsule , through the crus cerebri , down through the pons, and to the medullary pyramids , where about 90% of the axons cross to the contralateral side at the decussation of the pyramids. They then descend as the lateral corticospinal tract. These axons synapse with lower motor neurons in the ventral horns of all levels of the spinal cord. The remaining 10% of axons descend on

3150-556: The primary sensory cortex via the posterior limb of the internal capsule. Some of the "pain fibers" in the ALS deviate from their pathway towards the VPLN. In one such deviation, axons travel towards the reticular formation in the midbrain. The reticular formation then projects to a number of places including the hippocampus (to create memories about the pain), the centromedian nucleus (to cause diffuse, non-specific pain) and various parts of

3213-466: The rear-facing one is the posterior grey column and the interlinking one is the lateral grey column . The grey matter on the left and right side is connected by the grey commissure . The grey matter in the spinal cord consists of interneurons , as well as the cell bodies of projection neurons . Grey matter undergoes development and growth throughout childhood and adolescence. Recent studies using cross-sectional neuroimaging have shown that by around

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3276-399: The region its butterfly-shape. This central region surrounds the central canal , which is an extension of the fourth ventricle and contains cerebrospinal fluid. The spinal cord is elliptical in cross section, being compressed dorsolaterally. Two prominent grooves, or sulci, run along its length. The posterior median sulcus is the groove in the dorsal side, and the anterior median fissure

3339-399: The right and left posterior spinal arteries . These travel in the subarachnoid space and send branches into the spinal cord. They form anastomoses (connections) via the anterior and posterior segmental medullary arteries , which enter the spinal cord at various points along its length. The actual blood flow caudally through these arteries, derived from the posterior cerebral circulation,

3402-472: The secondary axon leaves its nucleus and passes anteriorly and medially. The collection of secondary axons that do this are known as internal arcuate fibers . The internal arcuate fibers decussate and continue ascending as the contralateral medial lemniscus . Secondary axons from the medial lemniscus finally terminate in the ventral posterolateral nucleus (VPLN) of the thalamus , where they synapse with tertiary neurons. From there, tertiary neurons ascend via

3465-458: The skin, muscles, and visceral organs to be relayed to the brain. The roots terminate in dorsal root ganglia , which are composed of the cell bodies of the corresponding neurons. Ventral roots consist of efferent fibers that arise from motor neurons whose cell bodies are found in the ventral (or anterior) gray horns of the spinal cord. The spinal cord (and brain) are protected by three layers of tissue or membranes called meninges , that surround

3528-427: The spinal cord and then ascend one to two levels before synapsing in the substantia gelatinosa . The tract that ascends before synapsing is known as Lissauer's tract . After synapsing, secondary axons decussate and ascend in the anterior lateral portion of the spinal cord as the spinothalamic tract . This tract ascends all the way to the VPLN, where it synapses on tertiary neurons. Tertiary neuronal axons then travel to

3591-427: The spinal cord is a continuation of the brainstem and anatomically begins at the occipital bone , passing out of the foramen magnum and then enters the spinal canal at the beginning of the cervical vertebrae . The spinal cord extends down to between the first and second lumbar vertebrae , where it tapers to become the cauda equina . The enclosing bony vertebral column protects the relatively shorter spinal cord. It

3654-409: The spinal cord to the coccyx . The cauda equina ("horse's tail") is a collection of nerves inferior to the conus medullaris that continue to travel through the vertebral column to the coccyx. The cauda equina forms because the spinal cord stops growing in length at about age four, even though the vertebral column continues to lengthen until adulthood. This results in sacral spinal nerves originating in

3717-455: The spinal cord via three tracts . Below L2, the proprioceptive information travels up the spinal cord in the ventral spinocerebellar tract . Also known as the anterior spinocerebellar tract, sensory receptors take in the information and travel into the spinal cord. The cell bodies of these primary neurons are located in the dorsal root ganglia . In the spinal cord, the axons synapse and the secondary neuronal axons decussates and then travel up to

3780-495: The spinal cord. Spinal nerves, with the exception of C1 and C2, form inside the intervertebral foramen . These rootlets form the demarcation between the central and peripheral nervous systems. Generally, the spinal cord segments do not correspond to bony vertebra levels. As the spinal cord terminates at the L1–L2 level, other segments of the spinal cord would be positioned superior to their corresponding bony vertebral body. For example,

3843-406: The spinal cord. The dorsal column–medial lemniscus pathway (DCML pathway), and the anterolateral system (ALS). In the dorsal column-medial lemniscus pathway, a primary neuron's axon enters the spinal cord and then enters the dorsal column. Here the dorsal column connects to the axon of the nerve cell. If the primary axon enters below spinal level T6, the axon travels in the gracile fasciculus ,

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3906-441: The upper lumbar region. For that reason, the spinal cord occupies only two-thirds of the vertebral canal. The inferior part of the vertebral canal is filled with cerebrospinal fluid and the space is called the lumbar cistern. Within the central nervous system (CNS), nerve cell bodies are generally organized into functional clusters, called nuclei , their axons are grouped into tracts . There are 31 spinal cord nerve segments in

3969-409: The vertebral column, the nerves of the lower spinal segments form a bundle called the cauda equina. There are two regions where the spinal cord enlarges: The spinal cord is supplied with blood by three arteries that run along its length starting in the brain, and many arteries that approach it through the sides of the spinal column. The three longitudinal arteries are the anterior spinal artery , and

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