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Encyclopedia > White matter

White matter is one of the two main solid components of the central nervous system. It is composed of myelinated nerve cell processes, or axons, which connect various grey matter areas (the locations of nerve cell bodies) of the brain to each other and carry nerve impulses between neurons. Cerebral and spinal white matter do not contain dendrites, which can only be found in grey matter along with neural cell bodies and shorter axons. A diagram showing the CNS: 1. ... In neuroscience, myelin is an electrically insulating phospholipid layer that surrounds the axons of many neurons. ... Drawing by Santiago Ramón y Cajal of cells in the pigeon cerebellum. ... An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... Grey matter is a major component of the central nervous system, consisting of nerve cell bodies and short nerve cell extensions/processes (axons and dendrites). ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. ... For other articles about other subjects named brain see brain (disambiguation). ... The term Dendrite stems from the Greek word dendron (literally “tree”), and typically refers to the branched projections of a neuron that act to conduct the electrical stimulation received from other cells to and from the cell body, or soma of the neuron from which the dendrites project. ... The soma is the bulbous end of a neuron, containing the nucleus. ...


Generally, white matter can be understood as the parts of the brain and spinal cord responsible for information transmission; whereas, grey matter is mainly responsible for information processing. Changes in white matter known as amyloid plaques are associated with Alzheimer's disease and other neurodegenerative diseases. White matter injuries ("axonal shearing") may be reversible, while grey matter regeneration is less likely. Amyloid describes various types of protein aggregations that share specific traits when examined microscopically. ...


White matter forms the bulk of the deep parts of the brain and the superficial parts of the spinal cord. Aggregates of grey matter such as the basal ganglia (caudate nucleus, putamen, globus pallidus, subthalamic nucleus, nucleus accumbens) and brain stem nuclei (red nucleus, substantia nigra, cranial nerve nuclei) are spread within the cerebral white matter. Cross-section through cervical spinal cord. ... The basal ganglia constitute one major subcortical system of the brain associated with motor and learning functions. ... Grays Fig. ... The putamen is a structure in the middle of the brain, forming the striatum together with the caudate nucleus. ... The globus pallidus (Latin for pale body) is a sub-cortical structure in the brain. ... The subthalamic nucleus is a small lens-shaped nucleus of the basal ganglia. ... The nucleus accumbens (also known as the accumbens nucleus or nucleus accumbens septi) is a collection of neurons located where the head of the caudate and the anterior portion of the putamen meet just lateral to the septum pellucidum. ... The red nucleus is a structure in the rostral midbrain involved in motor coordination. ... The substantia nigra (Latin for black substance) is a portion of the midbrain thought to be involved in certain aspects of movement and attention. ... Cranial nerves are nerves which start directly from the brainstem instead of the spinal cord. ...


The cerebellum is structured in a similar manner as the cerebrum, with a superficial mantle of cerebellar cortex, deep cerebellar white matter (called the "Arbor Vitae") and aggregates of grey matter surrounded by deep cerebellar white matter (dentate nucleus, globose nucleus, emboliform nucleus, and fastigial nucleus). The fluid-filled cerebral ventricles (lateral ventricles, third ventricle, cerebral aqueduct, fourth ventricle) are also located deep within the cerebral white matter. Figure 1a: A human brain, with the cerebellum in purple. ... The ventricular system is a set of structures in the brain continuous with the central canal of the spinal cord. ... The third ventricle is one of the four connected fluid-filled cavities within the human brain. ... The mesencephalic duct, also known as the aqueduct of Silvius or the cerebral aqueduct, contains cerebrospinal fluid (CSF), is within the mesencephalon (or midbrain) and connects the third ventricle in the thalamus (or diencephalon) to the fourth ventricle, which is between the pons and cerebellum. ... The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. ...


In 1983, M. C. Raff et al. discovered that tissue samples originating from rat optic nerve contained two morphologically distinct types of astrocytes. So-called Type 1 astrocytes had a fibroblast appearance and resided in both grey matter and white matter, whereas Type 2 astrocytes has a neuron-like appearance and resided in white matter alone (Sherman, Chris). Astrocytes, also known as astroglia, are characteristic star-shaped glial cells in the brain. ... A fibroblast is a cell that makes the structural fibers and ground substance of connective tissue. ...


In general, pathological liars have 22% more white matter compared with non-liars.[1]


Notes

  1. ^ Biever, Celeste (2005). Liars’ brains make fibbing come naturally. New Scientist. URL accessed on 13 May 2006.

External links

  • White Matter Atlas

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