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MATERIA GRIS | MÉDULA ESPINAL | NEUROLOGÍA

JD LECTURES・2 minutes read

The study delves into the gray matter of the spinal cord, divided into nucleus and cortex sections, and discusses the organization of this matter in rexel sheets. It explains the various nuclei within the gray matter responsible for sensory and motor functions and their specific roles in different spinal segments from cervical to lumbar levels.

Insights

  • The spinal cord's gray matter is divided into cortex and nuclei, with distinct functions related to sensation and motor control.
  • Specific nuclei and structures within the gray matter correspond to different spinal cord segments, playing essential roles in innervating various muscles and coordinating bodily functions.

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Recent questions

  • What is gray matter in the spinal cord?

    Gray matter in the spinal cord consists of nerve cells, dendrites, axons, and blood vessels. It is divided into cortex (neuronal bodies on the exposed surface) and nuclei (neuronal bodies embedded within the central nervous system).

  • What is the function of the posterior gray cords in the spinal cord?

    The posterior gray cords contain four groups of nerve cells, including the gelatinous substance group related to pain and touch sensations, the nucleus proprius for proprioception, Clark's dorsal nucleus extending from C8 to L3 or L4, and the lateral gray cords for sympathetic and parasympathetic fibers.

  • How is gray matter organized in the spinal cord?

    Gray matter in the spinal cord is further organized into 10 sheets called rexel sheets, aiding in the understanding of the spinal cord structure. These sheets help in identifying important nuclei within the gray matter and their corresponding positions.

  • What are the different nuclei present in the spinal cord's gray matter?

    The spinal cord contains various nuclei within the gray matter, such as the posterior marginal nucleus, red nucleus (Rolando's gelatinous substance), green nucleus (nucleus proprius), dorsal nucleus (Clark's column), and lateral intermediate nucleus. Each nucleus plays crucial roles in sensory and motor functions.

  • How does the amount of gray matter in the spinal cord correlate with muscle innervation?

    The amount of gray matter in the spinal cord is related to the muscle innervated by that level, with larger sizes in the cervical and lumbosacral regions. The cervical intumescence corresponds to the brachial plexus for upper extremities, while the lumbar intumescence corresponds to the lumbosacral plexus for lower extremities.

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Summary

00:00

Gray Matter Organization in Spinal Cord Neuroscience

  • The study focuses on the gray matter of the spinal cord, emphasizing the distinction between gray and white matter.
  • Neurons consist of a cell body, dendrites, and axons, with the axon covered by a myelin sheath.
  • The myelin sheath gives the white color to the region, known as white matter, while the absence of this sheath results in gray matter.
  • Neurons lacking a myelin sheath in the central nervous system are also considered part of the gray matter.
  • Gray matter can be divided into cortex (neuronal bodies on the exposed surface) and nuclei (neuronal bodies embedded within the central nervous system).
  • Ganglia, located outside the central nervous system, are distinct from gray matter and nuclei.
  • The gray matter of the spinal cord is H-shaped, with posterior or dorsal horns associated with sensations and anterior or ventral horns linked to motor functions.
  • The gray commissure, made up of unmyelinated axons, is considered gray matter.
  • The gray matter is further organized into 10 sheets called rexel sheets, aiding in the understanding of the spinal cord structure.
  • Important nuclei within the gray matter, such as the posterior marginal nucleus, play crucial roles in sensory and motor functions, with their positions corresponding to specific rexel sheets.

13:47

Spinal Cord Nuclei and Their Functions

  • The red nucleus is also known as Rolando's gelatinous substance and covers the rexet lamina, specifically rexel plate number 2.
  • The gelatinous substance can be found in all spinal segments, from cervical to lumbar levels.
  • The green nucleus, known as the nucleus proprius, includes lamina of rexet number 3 and 4, present in all spinal segments.
  • The dorsal nucleus, also called Clark's column, covers sheet number 7 and is limited to the spinal cord region from c8 to l3.
  • The lateral intermediate nucleus, part of the sympathetic nervous system, is present from T1 to L2.
  • In sacral segments S2 to S4, there are parasympathetic pre-ganglion neurons similar to the lateral horns, innervating sphincters and sexual muscles.
  • The medial group of neurons, located in rexet sheet number 9, innervates trunk and neck muscles in all spinal segments.
  • The middle group, situated between the medial and lateral groups, contains three nuclei: phrenic, accessory, and lumbosacral.
  • The phrenic nucleus, from C3 to C5, innervates the diaphragm, crucial for breathing.
  • The accessory nucleus, found between cervical segments 1 to 5, innervates the sternocleidomastoid and trapezius muscles.

28:12

Spinal Cord Nuclei and Innervation Summary

  • The spinal cord innervates sphincters like the external sphincter of wool, muscles for ejaculation and erection.
  • Three nuclei in the middle group include the phrenic nucleus (C3-C5), accessory nucleus (spinal portion of accessory nerve), and lumbosacral nucleus (S2-S4).
  • The lateral groups, present on both sides, innervate extremities, with more gray matter in regions like the cervical and lumbar intumescences.
  • Gray matter amount in the spinal cord's anterior horn correlates with the muscles innervated by neurons.
  • Cervical intumescence (C5-T1) corresponds to the brachial plexus for upper extremities, while lumbar intumescence (L2-S3) corresponds to the lumbosacral plexus for lower extremities.
  • The lateral group contains neurons from the cerebral cortex that synapse with lower motor neurons to innervate muscles.
  • The spinal cord segments show specific nuclei and structures like the phrenic nucleus, accessory nucleus, and gelatinous substance.
  • In thoracic segments like T2 and T6, lateral horns, pre-ganglion sympathetic outflows, and motoneurons for trunk muscles are observed.
  • Lumbar and sacral segments like L3 and L4 show the absence of lateral horns, presence of gelatinous substance, proper nucleus, and Clark's dorsal nucleus.
  • The sacral segment (S3) lacks Clark's dorsal nucleus but contains the gelatinous substance, proper nucleus, and parasympathetic pre-ganglion neurons for leg muscles.

41:21

Spinal Cord Gray Matter and Muscle Innervation

  • The amount of gray matter in the spinal cord is related to the muscle innervated by that level, with larger sizes in the cervical and lumbosacral regions, innervating upper and lower limb muscles respectively.
  • The gray matter in the spinal cord consists of nerve cells, dendrites, axons, and blood vessels, with nerve cells in the anterior gray cords classified into medial, central, and lateral groups based on their innervation responsibilities.
  • The medial group of nerve cells in the anterior gray cords innervates skeletal muscles of the neck and trunk, while the central group is smaller and present in specific segments like the cervical portion, responsible for muscles like the diaphragm.
  • The posterior gray cords contain four groups of nerve cells, including the gelatinous substance group related to pain and touch sensations, the nucleus proprius for proprioception, Clark's dorsal nucleus extending from C8 to L3 or L4, and the lateral gray cords for sympathetic and parasympathetic fibers.
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