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Содержание
Введение
Поддерживающие клетки в нервной системе
научный журнал
Support cells in the nervous system
the scientific journal
Глия, также называемая глиальными клетками (глиоцитами) или нейроглией, – это ненейронные клетки центральной нервной системы (головного и спинного мозга) и периферической нервной системы, которые не генерируют электрические импульсы. Нейроглии составляют более половины объема нервной ткани в организме человека. Они поддерживают гомеостаз, формируют миелиновую оболочку в периферической нервной системе и обеспечивают поддержку и защиту нейронов. В центральной нервной системе глиальные клетки включают олигодендроциты, астроциты, эпендимальные клетки и микроглию, а в периферической нервной системе – клетки Шванна и спутниковые клетки.
Glia, also called glial cells (gliocytes) or neuroglia, are non neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. The neuroglia make up more than one half the volume of neural tissue in the human body. They maintain homeostasis, form myelin in the peripheral nervous system, and provide support and protection for neurons. In the central nervous system, glial cells include oligodendrocytes, astrocytes, ependymal cells and microglia, and in the peripheral nervous system they include Schwann cells and satellite cells.
Макроглии
Получены из эктодермальной ткани. Наиболее распространенный тип макроглиальных клеток в ЦНС, астроциты (также называемые астроглиями) имеют многочисленные отростки, которые связывают нейроны с их кровоснабжением, формируя гематоэнцефалический барьер. Они регулируют внешнюю химическую среду нейронов, удаляя избыток ионов калия и перерабатывая нейротрансмиттеры, высвобождаемые во время синаптической передачи. Астроциты могут регулировать вазоконстрикцию и вазодилатацию, производя такие вещества, как арахидоновая кислота, метаболиты которой обладают вазоактивными свойствами. Астроциты передают друг другу сигналы с помощью АТФ. Щелевые контакты (также известные как электрические синапсы) между астроцитами позволяют молекуле-мессенджеру IP3 диффундировать от одного астроцита к другому. IP3 активирует кальциевые каналы на клеточных органеллах, высвобождая кальций в цитоплазму. Этот кальций может стимулировать выработку большего количества IP3 и вызывать высвобождение АТФ через каналы в мембране, образованные паннексинами. Конечным эффектом является волна кальция, распространяющаяся от клетки к клетке. Внеклеточный выброс АТФ и последующая активация пуринергических рецепторов на других астроцитах также могут опосредовать волны кальция в некоторых случаях. В целом, существует два типа астроцитов: протоплазматические и волокнистые, схожие по функции, но различающиеся по морфологии и распределению. Протоплазматические астроциты имеют короткие, толстые, сильно разветвленные отростки и обычно встречаются в сером веществе. Волокнистые астроциты имеют длинные, тонкие, менее разветвленные отростки и чаще встречаются в белом веществе. Недавно было показано, что активность астроцитов связана с мозговым кровотоком, и именно это измеряется при фМРТ. Они также участвуют в нейронных цепях, играя ингибирующую роль после обнаружения изменений во внеклеточном кальции.
Derived from ectodermal tissue. Location Name Description CNS Astrocytes The most abundant type of macroglial cell in the CNS, astrocytes (also called astroglia) have numerous projections that link neurons to their blood supply while forming the blood–brain barrier. They regulate the external chemical environment of neurons by removing excess potassium ions, and recycling neurotransmitters released during synaptic transmission. Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive. Astrocytes signal each other using ATP. The gap junctions (also known as electrical synapses) between astrocytes allow the messenger molecule IP3 to diffuse from one astrocyte to another. IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm. This calcium may stimulate the production of more IP3 and cause release of ATP through channels in the membrane made of pannexins. The net effect is a calcium wave that propagates from cell to cell. Extracellular release of ATP, and consequent activation of purinergic receptors on other astrocytes, may also mediate calcium waves in some cases. In general, there are two types of astrocytes, protoplasmic and fibrous, similar in function but distinct in morphology and distribution. Protoplasmic astrocytes have short, thick, highly branched processes and are typically found in gray matter. Fibrous astrocytes have long, thin, less branched processes and are more commonly found in white matter. It has recently been shown that astrocyte activity is linked to blood flow in the brain, and that this is what is actually being measured in fMRI. They also have been involved in neuronal circuits playing an inhibitory role after sensing changes in extracellular calcium. CNS Oligodendrocytes Oligodendrocytes are cells that coat axons in the CNS with their cell membrane, forming a specialized membrane differentiation called myelin, producing the myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently. CNS Ependymal cells Ependymal cells, also named ependymocytes, line the spinal cord and the ventricular system of the brain. These cells are involved in the creation and secretion of cerebrospinal fluid (CSF) and beat their cilia to help circulate the CSF and make up the blood CSF barrier. They are also thought to act as neural stem cells. CNS Radial glia Radial glia cells arise from neuroepithelial cells after the onset of neurogenesis. Their differentiation abilities are more restricted than those of neuroepithelial cells. In the developing nervous system, radial glia function both as neuronal progenitors and as a scaffold upon which newborn neurons migrate. In the mature brain, the cerebellum and retina retain characteristic radial glial cells. In the cerebellum, these are Bergmann glia, which regulate synaptic plasticity. In the retina, the radial Müller cell is the glial cell that spans the thickness of the retina and, in addition to astroglial cells, participates in a bidirectional communication with neurons. PNS Schwann cells Similar in function to oligodendrocytes, Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons. PNS Satellite cells Satellite glial cells are small cells that surround neurons in sensory, sympathetic, and parasympathetic ganglia. These cells help regulate the external chemical environment. Like astrocytes, they are interconnected by gap junctions and respond to ATP by elevating the intracellular concentration of calcium ions. They are highly sensitive to injury and inflammation and appear to contribute to pathological states, such as chronic pain. PNS Enteric glial cellsAre found in the intrinsic ganglia of the digestive system. Glia cells are thought to have many roles in the enteric system, some related to homeostasis and muscular digestive processes.
Олигодендроциты ЦНС. Олигодендроциты – это клетки, которые покрывают аксоны в ЦНС своей клеточной мембраной, формируя специализированную мембранную дифференцировку, называемую миелином, и производя миелиновую оболочку. Миелиновая оболочка обеспечивает изоляцию аксона, что позволяет электрическим сигналам распространяться более эффективно.
Derived from ectodermal tissue. Location Name Description CNS Astrocytes The most abundant type of macroglial cell in the CNS, astrocytes (also called astroglia) have numerous projections that link neurons to their blood supply while forming the blood–brain barrier. They regulate the external chemical environment of neurons by removing excess potassium ions, and recycling neurotransmitters released during synaptic transmission. Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive. Astrocytes signal each other using ATP. The gap junctions (also known as electrical synapses) between astrocytes allow the messenger molecule IP3 to diffuse from one astrocyte to another. IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm. This calcium may stimulate the production of more IP3 and cause release of ATP through channels in the membrane made of pannexins. The net effect is a calcium wave that propagates from cell to cell. Extracellular release of ATP, and consequent activation of purinergic receptors on other astrocytes, may also mediate calcium waves in some cases. In general, there are two types of astrocytes, protoplasmic and fibrous, similar in function but distinct in morphology and distribution. Protoplasmic astrocytes have short, thick, highly branched processes and are typically found in gray matter. Fibrous astrocytes have long, thin, less branched processes and are more commonly found in white matter. It has recently been shown that astrocyte activity is linked to blood flow in the brain, and that this is what is actually being measured in fMRI. They also have been involved in neuronal circuits playing an inhibitory role after sensing changes in extracellular calcium. CNS Oligodendrocytes Oligodendrocytes are cells that coat axons in the CNS with their cell membrane, forming a specialized membrane differentiation called myelin, producing the myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently. CNS Ependymal cells Ependymal cells, also named ependymocytes, line the spinal cord and the ventricular system of the brain. These cells are involved in the creation and secretion of cerebrospinal fluid (CSF) and beat their cilia to help circulate the CSF and make up the blood CSF barrier. They are also thought to act as neural stem cells. CNS Radial glia Radial glia cells arise from neuroepithelial cells after the onset of neurogenesis. Their differentiation abilities are more restricted than those of neuroepithelial cells. In the developing nervous system, radial glia function both as neuronal progenitors and as a scaffold upon which newborn neurons migrate. In the mature brain, the cerebellum and retina retain characteristic radial glial cells. In the cerebellum, these are Bergmann glia, which regulate synaptic plasticity. In the retina, the radial Müller cell is the glial cell that spans the thickness of the retina and, in addition to astroglial cells, participates in a bidirectional communication with neurons. PNS Schwann cells Similar in function to oligodendrocytes, Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons. PNS Satellite cells Satellite glial cells are small cells that surround neurons in sensory, sympathetic, and parasympathetic ganglia. These cells help regulate the external chemical environment. Like astrocytes, they are interconnected by gap junctions and respond to ATP by elevating the intracellular concentration of calcium ions. They are highly sensitive to injury and inflammation and appear to contribute to pathological states, such as chronic pain. PNS Enteric glial cellsAre found in the intrinsic ganglia of the digestive system. Glia cells are thought to have many roles in the enteric system, some related to homeostasis and muscular digestive processes.
Эпендимальные клетки, также называемые эпендимоцитами, выстилают спинной мозг и желудочковую систему мозга. Эти клетки участвуют в создании и секреции спинномозговой жидкости (СМЖ) и бьют своими ресничками, чтобы способствовать циркуляции СМЖ и формированию гематоспинномозгового барьера. Считается, что они также могут выступать в качестве нейральных стволовых клеток.
Derived from ectodermal tissue. Location Name Description CNS Astrocytes The most abundant type of macroglial cell in the CNS, astrocytes (also called astroglia) have numerous projections that link neurons to their blood supply while forming the blood–brain barrier. They regulate the external chemical environment of neurons by removing excess potassium ions, and recycling neurotransmitters released during synaptic transmission. Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive. Astrocytes signal each other using ATP. The gap junctions (also known as electrical synapses) between astrocytes allow the messenger molecule IP3 to diffuse from one astrocyte to another. IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm. This calcium may stimulate the production of more IP3 and cause release of ATP through channels in the membrane made of pannexins. The net effect is a calcium wave that propagates from cell to cell. Extracellular release of ATP, and consequent activation of purinergic receptors on other astrocytes, may also mediate calcium waves in some cases. In general, there are two types of astrocytes, protoplasmic and fibrous, similar in function but distinct in morphology and distribution. Protoplasmic astrocytes have short, thick, highly branched processes and are typically found in gray matter. Fibrous astrocytes have long, thin, less branched processes and are more commonly found in white matter. It has recently been shown that astrocyte activity is linked to blood flow in the brain, and that this is what is actually being measured in fMRI. They also have been involved in neuronal circuits playing an inhibitory role after sensing changes in extracellular calcium. CNS Oligodendrocytes Oligodendrocytes are cells that coat axons in the CNS with their cell membrane, forming a specialized membrane differentiation called myelin, producing the myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently. CNS Ependymal cells Ependymal cells, also named ependymocytes, line the spinal cord and the ventricular system of the brain. These cells are involved in the creation and secretion of cerebrospinal fluid (CSF) and beat their cilia to help circulate the CSF and make up the blood CSF barrier. They are also thought to act as neural stem cells. CNS Radial glia Radial glia cells arise from neuroepithelial cells after the onset of neurogenesis. Their differentiation abilities are more restricted than those of neuroepithelial cells. In the developing nervous system, radial glia function both as neuronal progenitors and as a scaffold upon which newborn neurons migrate. In the mature brain, the cerebellum and retina retain characteristic radial glial cells. In the cerebellum, these are Bergmann glia, which regulate synaptic plasticity. In the retina, the radial Müller cell is the glial cell that spans the thickness of the retina and, in addition to astroglial cells, participates in a bidirectional communication with neurons. PNS Schwann cells Similar in function to oligodendrocytes, Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons. PNS Satellite cells Satellite glial cells are small cells that surround neurons in sensory, sympathetic, and parasympathetic ganglia. These cells help regulate the external chemical environment. Like astrocytes, they are interconnected by gap junctions and respond to ATP by elevating the intracellular concentration of calcium ions. They are highly sensitive to injury and inflammation and appear to contribute to pathological states, such as chronic pain. PNS Enteric glial cellsAre found in the intrinsic ganglia of the digestive system. Glia cells are thought to have many roles in the enteric system, some related to homeostasis and muscular digestive processes.
Радиальная глия ЦНС. Радиальные глиальные клетки происходят из нейроэпителиальных клеток после начала нейрогенеза. Их способность к дифференцировке более ограничена, чем у нейроэпителиальных клеток. В развивающейся нервной системе радиальная глия функционирует как предшественники нейронов и как каркас, по которому мигрируют новорожденные нейроны. В зрелом мозге мозжечок и сетчатка сохраняют характерные радиальные глиальные клетки. В мозжечке это клетки Бергмана, которые регулируют синаптическую пластичность. В сетчатке радиальная клетка Мюллера является глиальной клеткой, которая охватывает толщину сетчатки и, помимо астроглиальных клеток, участвует в двунаправленной коммуникации с нейронами.
Derived from ectodermal tissue. Location Name Description CNS Astrocytes The most abundant type of macroglial cell in the CNS, astrocytes (also called astroglia) have numerous projections that link neurons to their blood supply while forming the blood–brain barrier. They regulate the external chemical environment of neurons by removing excess potassium ions, and recycling neurotransmitters released during synaptic transmission. Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive. Astrocytes signal each other using ATP. The gap junctions (also known as electrical synapses) between astrocytes allow the messenger molecule IP3 to diffuse from one astrocyte to another. IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm. This calcium may stimulate the production of more IP3 and cause release of ATP through channels in the membrane made of pannexins. The net effect is a calcium wave that propagates from cell to cell. Extracellular release of ATP, and consequent activation of purinergic receptors on other astrocytes, may also mediate calcium waves in some cases. In general, there are two types of astrocytes, protoplasmic and fibrous, similar in function but distinct in morphology and distribution. Protoplasmic astrocytes have short, thick, highly branched processes and are typically found in gray matter. Fibrous astrocytes have long, thin, less branched processes and are more commonly found in white matter. It has recently been shown that astrocyte activity is linked to blood flow in the brain, and that this is what is actually being measured in fMRI. They also have been involved in neuronal circuits playing an inhibitory role after sensing changes in extracellular calcium. CNS Oligodendrocytes Oligodendrocytes are cells that coat axons in the CNS with their cell membrane, forming a specialized membrane differentiation called myelin, producing the myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently. CNS Ependymal cells Ependymal cells, also named ependymocytes, line the spinal cord and the ventricular system of the brain. These cells are involved in the creation and secretion of cerebrospinal fluid (CSF) and beat their cilia to help circulate the CSF and make up the blood CSF barrier. They are also thought to act as neural stem cells. CNS Radial glia Radial glia cells arise from neuroepithelial cells after the onset of neurogenesis. Their differentiation abilities are more restricted than those of neuroepithelial cells. In the developing nervous system, radial glia function both as neuronal progenitors and as a scaffold upon which newborn neurons migrate. In the mature brain, the cerebellum and retina retain characteristic radial glial cells. In the cerebellum, these are Bergmann glia, which regulate synaptic plasticity. In the retina, the radial Müller cell is the glial cell that spans the thickness of the retina and, in addition to astroglial cells, participates in a bidirectional communication with neurons. PNS Schwann cells Similar in function to oligodendrocytes, Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons. PNS Satellite cells Satellite glial cells are small cells that surround neurons in sensory, sympathetic, and parasympathetic ganglia. These cells help regulate the external chemical environment. Like astrocytes, they are interconnected by gap junctions and respond to ATP by elevating the intracellular concentration of calcium ions. They are highly sensitive to injury and inflammation and appear to contribute to pathological states, such as chronic pain. PNS Enteric glial cellsAre found in the intrinsic ganglia of the digestive system. Glia cells are thought to have many roles in the enteric system, some related to homeostasis and muscular digestive processes.
PNS. Клетки Шванна. По своей функции схожи с олигодендроцитами, клетки Шванна обеспечивают миелинизацию аксонов в периферической нервной системе (PNS). Они также обладают фагоцитозной активностью и удаляют клеточный детрит, что способствует регенерации нейронов PNS.
Derived from ectodermal tissue. Location Name Description CNS Astrocytes The most abundant type of macroglial cell in the CNS, astrocytes (also called astroglia) have numerous projections that link neurons to their blood supply while forming the blood–brain barrier. They regulate the external chemical environment of neurons by removing excess potassium ions, and recycling neurotransmitters released during synaptic transmission. Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive. Astrocytes signal each other using ATP. The gap junctions (also known as electrical synapses) between astrocytes allow the messenger molecule IP3 to diffuse from one astrocyte to another. IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm. This calcium may stimulate the production of more IP3 and cause release of ATP through channels in the membrane made of pannexins. The net effect is a calcium wave that propagates from cell to cell. Extracellular release of ATP, and consequent activation of purinergic receptors on other astrocytes, may also mediate calcium waves in some cases. In general, there are two types of astrocytes, protoplasmic and fibrous, similar in function but distinct in morphology and distribution. Protoplasmic astrocytes have short, thick, highly branched processes and are typically found in gray matter. Fibrous astrocytes have long, thin, less branched processes and are more commonly found in white matter. It has recently been shown that astrocyte activity is linked to blood flow in the brain, and that this is what is actually being measured in fMRI. They also have been involved in neuronal circuits playing an inhibitory role after sensing changes in extracellular calcium. CNS Oligodendrocytes Oligodendrocytes are cells that coat axons in the CNS with their cell membrane, forming a specialized membrane differentiation called myelin, producing the myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently. CNS Ependymal cells Ependymal cells, also named ependymocytes, line the spinal cord and the ventricular system of the brain. These cells are involved in the creation and secretion of cerebrospinal fluid (CSF) and beat their cilia to help circulate the CSF and make up the blood CSF barrier. They are also thought to act as neural stem cells. CNS Radial glia Radial glia cells arise from neuroepithelial cells after the onset of neurogenesis. Their differentiation abilities are more restricted than those of neuroepithelial cells. In the developing nervous system, radial glia function both as neuronal progenitors and as a scaffold upon which newborn neurons migrate. In the mature brain, the cerebellum and retina retain characteristic radial glial cells. In the cerebellum, these are Bergmann glia, which regulate synaptic plasticity. In the retina, the radial Müller cell is the glial cell that spans the thickness of the retina and, in addition to astroglial cells, participates in a bidirectional communication with neurons. PNS Schwann cells Similar in function to oligodendrocytes, Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons. PNS Satellite cells Satellite glial cells are small cells that surround neurons in sensory, sympathetic, and parasympathetic ganglia. These cells help regulate the external chemical environment. Like astrocytes, they are interconnected by gap junctions and respond to ATP by elevating the intracellular concentration of calcium ions. They are highly sensitive to injury and inflammation and appear to contribute to pathological states, such as chronic pain. PNS Enteric glial cellsAre found in the intrinsic ganglia of the digestive system. Glia cells are thought to have many roles in the enteric system, some related to homeostasis and muscular digestive processes.
PNS. Спутниковые клетки. Спутниковые глиальные клетки – это небольшие клетки, окружающие нейроны в сенсорных, симпатических и парасимпатических ганглиях. Эти клетки помогают регулировать внешнюю химическую среду. Как и астроциты, они соединены между собой щелевыми контактами и реагируют на АТФ, повышая внутриклеточную концентрацию ионов кальция. Они очень чувствительны к повреждениям и воспалению и, по-видимому, способствуют развитию патологических состояний, таких как хроническая боль.
Derived from ectodermal tissue. Location Name Description CNS Astrocytes The most abundant type of macroglial cell in the CNS, astrocytes (also called astroglia) have numerous projections that link neurons to their blood supply while forming the blood–brain barrier. They regulate the external chemical environment of neurons by removing excess potassium ions, and recycling neurotransmitters released during synaptic transmission. Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive. Astrocytes signal each other using ATP. The gap junctions (also known as electrical synapses) between astrocytes allow the messenger molecule IP3 to diffuse from one astrocyte to another. IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm. This calcium may stimulate the production of more IP3 and cause release of ATP through channels in the membrane made of pannexins. The net effect is a calcium wave that propagates from cell to cell. Extracellular release of ATP, and consequent activation of purinergic receptors on other astrocytes, may also mediate calcium waves in some cases. In general, there are two types of astrocytes, protoplasmic and fibrous, similar in function but distinct in morphology and distribution. Protoplasmic astrocytes have short, thick, highly branched processes and are typically found in gray matter. Fibrous astrocytes have long, thin, less branched processes and are more commonly found in white matter. It has recently been shown that astrocyte activity is linked to blood flow in the brain, and that this is what is actually being measured in fMRI. They also have been involved in neuronal circuits playing an inhibitory role after sensing changes in extracellular calcium. CNS Oligodendrocytes Oligodendrocytes are cells that coat axons in the CNS with their cell membrane, forming a specialized membrane differentiation called myelin, producing the myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently. CNS Ependymal cells Ependymal cells, also named ependymocytes, line the spinal cord and the ventricular system of the brain. These cells are involved in the creation and secretion of cerebrospinal fluid (CSF) and beat their cilia to help circulate the CSF and make up the blood CSF barrier. They are also thought to act as neural stem cells. CNS Radial glia Radial glia cells arise from neuroepithelial cells after the onset of neurogenesis. Their differentiation abilities are more restricted than those of neuroepithelial cells. In the developing nervous system, radial glia function both as neuronal progenitors and as a scaffold upon which newborn neurons migrate. In the mature brain, the cerebellum and retina retain characteristic radial glial cells. In the cerebellum, these are Bergmann glia, which regulate synaptic plasticity. In the retina, the radial Müller cell is the glial cell that spans the thickness of the retina and, in addition to astroglial cells, participates in a bidirectional communication with neurons. PNS Schwann cells Similar in function to oligodendrocytes, Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons. PNS Satellite cells Satellite glial cells are small cells that surround neurons in sensory, sympathetic, and parasympathetic ganglia. These cells help regulate the external chemical environment. Like astrocytes, they are interconnected by gap junctions and respond to ATP by elevating the intracellular concentration of calcium ions. They are highly sensitive to injury and inflammation and appear to contribute to pathological states, such as chronic pain. PNS Enteric glial cellsAre found in the intrinsic ganglia of the digestive system. Glia cells are thought to have many roles in the enteric system, some related to homeostasis and muscular digestive processes.
PNS. Энтеральные глиальные клетки. Обнаружены во внутриорганных ганглиях пищеварительной системы. Считается, что глиальные клетки играют множество ролей в энтеральной системе, некоторые из которых связаны с гомеостазом и мышечными процессами пищеварения.
Derived from ectodermal tissue. Location Name Description CNS Astrocytes The most abundant type of macroglial cell in the CNS, astrocytes (also called astroglia) have numerous projections that link neurons to their blood supply while forming the blood–brain barrier. They regulate the external chemical environment of neurons by removing excess potassium ions, and recycling neurotransmitters released during synaptic transmission. Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive. Astrocytes signal each other using ATP. The gap junctions (also known as electrical synapses) between astrocytes allow the messenger molecule IP3 to diffuse from one astrocyte to another. IP3 activates calcium channels on cellular organelles, releasing calcium into the cytoplasm. This calcium may stimulate the production of more IP3 and cause release of ATP through channels in the membrane made of pannexins. The net effect is a calcium wave that propagates from cell to cell. Extracellular release of ATP, and consequent activation of purinergic receptors on other astrocytes, may also mediate calcium waves in some cases. In general, there are two types of astrocytes, protoplasmic and fibrous, similar in function but distinct in morphology and distribution. Protoplasmic astrocytes have short, thick, highly branched processes and are typically found in gray matter. Fibrous astrocytes have long, thin, less branched processes and are more commonly found in white matter. It has recently been shown that astrocyte activity is linked to blood flow in the brain, and that this is what is actually being measured in fMRI. They also have been involved in neuronal circuits playing an inhibitory role after sensing changes in extracellular calcium. CNS Oligodendrocytes Oligodendrocytes are cells that coat axons in the CNS with their cell membrane, forming a specialized membrane differentiation called myelin, producing the myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently. CNS Ependymal cells Ependymal cells, also named ependymocytes, line the spinal cord and the ventricular system of the brain. These cells are involved in the creation and secretion of cerebrospinal fluid (CSF) and beat their cilia to help circulate the CSF and make up the blood CSF barrier. They are also thought to act as neural stem cells. CNS Radial glia Radial glia cells arise from neuroepithelial cells after the onset of neurogenesis. Their differentiation abilities are more restricted than those of neuroepithelial cells. In the developing nervous system, radial glia function both as neuronal progenitors and as a scaffold upon which newborn neurons migrate. In the mature brain, the cerebellum and retina retain characteristic radial glial cells. In the cerebellum, these are Bergmann glia, which regulate synaptic plasticity. In the retina, the radial Müller cell is the glial cell that spans the thickness of the retina and, in addition to astroglial cells, participates in a bidirectional communication with neurons. PNS Schwann cells Similar in function to oligodendrocytes, Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons. PNS Satellite cells Satellite glial cells are small cells that surround neurons in sensory, sympathetic, and parasympathetic ganglia. These cells help regulate the external chemical environment. Like astrocytes, they are interconnected by gap junctions and respond to ATP by elevating the intracellular concentration of calcium ions. They are highly sensitive to injury and inflammation and appear to contribute to pathological states, such as chronic pain. PNS Enteric glial cellsAre found in the intrinsic ganglia of the digestive system. Glia cells are thought to have many roles in the enteric system, some related to homeostasis and muscular digestive processes.
Микроглии
Микроглии – это специализированные макрофаги, способные к фагоцитозу, которые защищают нейроны центральной нервной системы. Они происходят из первой волны мононуклеарных клеток, возникающих в кровяных островках желточного мешка на ранних стадиях развития, и колонизируют мозг вскоре после начала дифференцировки нейронных предшественников. Эти клетки обнаружены во всех областях мозга и спинного мозга. Микроглиальные клетки относительно малы по сравнению с макроглиальными клетками, имеют изменчивую форму и продолговатые ядра. Они подвижны в мозге и пролиферируют при повреждении мозга. В здоровой центральной нервной системе отростки микроглии постоянно сканируют все аспекты окружающей среды (нейроны, макроглию и кровеносные сосуды). В здоровом мозге микроглии направляют иммунный ответ при повреждении мозга и играют важную роль в воспалении, которое сопровождает это повреждение. Многие заболевания и расстройства связаны с дисфункцией микроглии, такие как болезнь Альцгеймера, болезнь Паркинсона и БАС.
Microglia are specialized macrophages capable of phagocytosis that protect neurons of the central nervous system. They are derived from the earliest wave of mononuclear cells that originate in yolk sac blood islands early in development, and colonize the brain shortly after the neural precursors begin to differentiate. These cells are found in all regions of the brain and spinal cord. Microglial cells are small relative to macroglial cells, with changing shapes and oblong nuclei. They are mobile within the brain and multiply when the brain is damaged. In the healthy central nervous system, microglia processes constantly sample all aspects of their environment (neurons, macroglia and blood vessels). In a healthy brain, microglia direct the immune response to brain damage and play an important role in the inflammation that accompanies the damage. Many diseases and disorders are associated with deficient microglia, such as Alzheimer's disease, Parkinson's disease and ALS.
Другое
Питуциты задней доли гипофиза – это глиальные клетки, обладающие характеристиками, схожими с астроцитами. Танициты в срединной возвышенности гипоталамуса представляют собой тип эпендимальных клеток, происходящих из радиальной глии и выстилающих основание третьего желудочка. Дрозофила melanogaster, или плодовая мушка, содержит множество типов глии, функционально аналогичных глии млекопитающих, но, тем не менее, классифицируемых иначе.
Pituicytes from the posterior pituitary are glial cells with characteristics in common to astrocytes. Tanycytes in the median eminence of the hypothalamus are a type of ependymal cell that descend from radial glia and line the base of the third ventricle. Drosophila melanogaster, the fruit fly, contains numerous glial types that are functionally similar to mammalian glia but are nonetheless classified differently.
Общее число
В общем, нейроглиальные клетки меньше нейронов. В человеческом мозге насчитывается около 85 миллиардов клеток глии, примерно столько же, сколько и нейронов. Соотношение глии к нейронам варьируется в разных частях мозга. В коре головного мозга это соотношение составляет 3,72 (60,84 миллиарда клеток глии (72%); 16,34 миллиарда нейронов), тогда как в мозжечке – всего 0,23 (16,04 миллиарда клеток глии; 69,03 миллиарда нейронов). Соотношение в сером веществе коры головного мозга составляет 1,48, а в сером и белом веществе вместе взятых – 3,76. Исследования о способности к митозу все еще продолжаются. Ранее считалось, что глия лишена некоторых характеристик, присущих нейронам. Например, полагали, что глиальные клетки не имеют химических синапсов и не высвобождают нейромедиаторы. Их рассматривали как пассивных наблюдателей нейротрансмиссии. Однако недавние исследования показали, что это не совсем верно.
In general, neuroglial cells are smaller than neurons. There are approximately 85 billion glia cells in the human brain, about the same number as neurons. The glia to neuron ratio varies from one part of the brain to another. The glia to neuron ratio in the cerebral cortex is 3.72 (60.84 billion glia (72%); 16.34 billion neurons), while that of the cerebellum is only 0.23 (16.04 billion glia; 69.03 billion neurons). The ratio in the cerebral cortex gray matter is 1.48, with 3.76 for the gray and white matter combined. or capable of mitosis, is still developing. In the past, glia had been considered to lack certain features of neurons. For example, glial cells were not believed to have chemical synapses or to release transmitters. They were considered to be the passive bystanders of neural transmission. However, recent studies have shown this to not be entirely true.
Функции
Некоторые глиальные клетки выполняют преимущественно опорную функцию для нейронов. Другие обеспечивают нейроны питательными веществами и регулируют внеклеточную жидкость мозга, особенно в области нейронов и их синапсов. В период раннего эмбриогенеза глиальные клетки направляют миграцию нейронов и вырабатывают молекулы, модифицирующие рост аксонов и дендритов. Определенные глиальные клетки демонстрируют региональную специфичность в ЦНС, и их функции могут различаться в разных областях ЦНС.
Some glial cells function primarily as the physical support for neurons. Others provide nutrients to neurons and regulate the extracellular fluid of the brain, especially surrounding neurons and their synapses. During early embryogenesis, glial cells direct the migration of neurons and produce molecules that modify the growth of axons and dendrites. Some glial cells display regional diversity in the CNS and their functions may vary between the CNS regions.
Ремонт и развитие нейронов
Глия играет решающую роль в развитии нервной системы, а также в таких процессах, как синаптическая пластичность и синаптогенез. Глия участвует в регуляции восстановления нейронов после повреждений. В центральной нервной системе (ЦНС) глия подавляет восстановление. Глиальные клетки, известные как астроциты, увеличиваются в размерах и пролиферируют, формируя глиальный рубец и производя ингибирующие молекулы, которые препятствуют регенерации поврежденного или перерезанного аксона. В периферической нервной системе (ПНС) глиальные клетки, известные как клетки Шванна (или нейролеммоциты), способствуют восстановлению. После повреждения аксона клетки Шванна возвращаются к более ранней стадии развития, стимулируя его повторный рост. Эта разница между ЦНС и ПНС вселяет надежду на регенерацию нервной ткани в ЦНС. Например, спинной мозг может быть восстановлен после травмы или перерезания.
Glia are crucial in the development of the nervous system and in processes such as synaptic plasticity and synaptogenesis. Glia have a role in the regulation of repair of neurons after injury. In the central nervous system (CNS), glia suppress repair. Glial cells known as astrocytes enlarge and proliferate to form a scar and produce inhibitory molecules that inhibit regrowth of a damaged or severed axon. In the peripheral nervous system (PNS), glial cells known as Schwann cells (or also as neuri lemmocytes) promote repair. After axonal injury, Schwann cells regress to an earlier developmental state to encourage regrowth of the axon. This difference between the CNS and the PNS, raises hopes for the regeneration of nervous tissue in the CNS. For example, a spinal cord may be able to be repaired following injury or severance.
Создание миелиновой оболочки
Олигодендроциты находятся в ЦНС и напоминают осьминога: у них округлые клеточные тела с до пятнадцати отростков, похожих на щупальца. Каждый отросток достигает аксона и спирально обвивается вокруг него, формируя миелиновую оболочку. Миелиновая оболочка изолирует нервное волокно от внеклеточной жидкости и ускоряет проведение сигнала по нервному волокну. В периферической нервной системе за образование миелина отвечают клетки Шванна. Эти клетки охватывают нервные волокна ПНС, многократно обвиваясь вокруг них. Этот процесс создает миелиновую оболочку, которая не только способствует проводимости, но и помогает в регенерации поврежденных волокон.
Oligodendrocytes are found in the CNS and resemble an octopus: they have bulbous cell bodies with up to fifteen arm like processes. Each process reaches out to an axon and spirals around it, creating a myelin sheath. The myelin sheath insulates the nerve fiber from the extracellular fluid and speeds up signal conduction along the nerve fiber. In the peripheral nervous system, Schwann cells are responsible for myelin production. These cells envelop nerve fibers of the PNS by winding repeatedly around them. This process creates a myelin sheath, which not only aids in conductivity but also assists in the regeneration of damaged fibers.
Нейротрансмиссия
Астроциты играют ключевую роль в трипартном синапсе. Они выполняют несколько важных функций, включая удаление нейротрансмиттеров из синаптической щели, что способствует различению отдельных потенциалов действия и предотвращает токсическое накопление определенных нейротрансмиттеров, таких как глутамат, которое в противном случае привело бы к возбуждающей токсичности. Более того, астроциты высвобождают глиотрансмиттеры, такие как глутамат, АТФ и D-серин в ответ на стимуляцию.
Astrocytes are crucial participants in the tripartite synapse. They have several crucial functions, including clearance of neurotransmitters from within the synaptic cleft, which aids in distinguishing between separate action potentials and prevents toxic build up of certain neurotransmitters such as glutamate, which would otherwise lead to excitotoxicity. Furthermore, astrocytes release gliotransmitters such as glutamate, ATP, and D serine in response to stimulation.
Клиническое значение
В то время как глиальные клетки в периферической нервной системе часто способствуют регенерации утраченной нервной функции, потеря нейронов в центральной нервной системе не вызывает аналогичной реакции со стороны нейроглии. Помимо влияния на потенциальное восстановление нейронов при болезни Альцгеймера, рубцевание и воспаление, вызванные глиальными клетками, дополнительно вовлечены в дегенерацию нейронов, обусловленную боковым амиотрофическим склерозом. Помимо нейродегенеративных заболеваний, широкий спектр вредных факторов, таких как гипоксия или физическая травма, может приводить к физическому повреждению центральной нервной системы.
While glial cells in the PNS frequently assist in regeneration of lost neural functioning, loss of neurons in the CNS does not result in a similar reaction from neuroglia. In addition to affecting the potential repair of neurons in Alzheimer's disease, scarring and inflammation from glial cells have been further implicated in the degeneration of neurons caused by amyotrophic lateral sclerosis. In addition to neurodegenerative diseases, a wide range of harmful exposure, such as hypoxia, or physical trauma, can lead to the result of physical damage to the CNS.
История
Хотя глиальные клетки и нейроны, вероятно, были впервые замечены одновременно в начале 19 века, в отличие от нейронов, морфологические и физиологические свойства которых были непосредственно наблюдаемы для первых исследователей нервной системы, глиальные клетки до середины 20 века считались лишь "клеем", удерживающим нейроны вместе. Глиа впервые были описаны в 1856 году патологом Рудольфом Вирховым в комментарии к его публикации 1846 года о соединительной ткани. Более подробное описание глиальных клеток было представлено в книге 1858 года "Клеточная патология" того же автора. При анализе маркеров для различных типов клеток было обнаружено, что мозг Альберта Эйнштейна содержит значительно больше глии, чем обычные мозги, в левой угловой извилине – области, предположительно отвечающей за математическую обработку и язык. Однако, учитывая общее число в 28 статистических сравнений между мозгом Эйнштейна и контрольными образцами, обнаружение одного статистически значимого результата не является неожиданным, и утверждение об отличии мозга Эйнштейна не имеет научного обоснования (ср. проблема множественных сравнений). Эволюция увеличивает не только соотношение глии к нейронам, но и размер глиальных клеток. Объем астроглиальных клеток в мозге человека в 27 раз превышает объем клеток в мозге мыши. Эти важные научные открытия могут начать смещать нейроцентрическую точку зрения в сторону более целостного взгляда на мозг, включающего и глиальные клетки. На протяжении большей части двадцатого века ученые пренебрегали глиальными клетками, рассматривая их лишь как физический каркас для нейронов. Недавние публикации предполагают, что количество глиальных клеток в мозге коррелирует с интеллектом вида. Более того, данные свидетельствуют об активной роли глии, в частности астроглии, в когнитивных процессах, таких как обучение и память, и по этой причине было предложено создание отдельной области исследований для изучения этих функций, поскольку исследования в этой области все еще ограничены из-за доминирования нейроцентрической перспективы.
Although glial cells and neurons were probably first observed at the same time in the early 19th century, unlike neurons whose morphological and physiological properties were directly observable for the first investigators of the nervous system, glial cells had been considered to be merely "glue" that held neurons together until the mid 20th century. Glia were first described in 1856 by the pathologist Rudolf Virchow in a comment to his 1846 publication on connective tissue. A more detailed description of glial cells was provided in the 1858 book 'Cellular Pathology' by the same author. When markers for different types of cells were analyzed, Albert Einstein's brain was discovered to contain significantly more glia than normal brains in the left angular gyrus, an area thought to be responsible for mathematical processing and language. However, out of the total of 28 statistical comparisons between Einstein's brain and the control brains, finding one statistically significant result is not surprising, and the claim that Einstein's brain is different is not scientific (c. f. Multiple comparisons problem). Not only does the ratio of glia to neurons increase through evolution, but so does the size of the glia. Astroglial cells in human brains have a volume 27 times greater than in mouse brains. These important scientific findings may begin to shift the neurocentric perspective into a more holistic view of the brain which encompasses the glial cells as well. For the majority of the twentieth century, scientists had disregarded glial cells as mere physical scaffolds for neurons. Recent publications have proposed that the number of glial cells in the brain is correlated with the intelligence of a species. Moreover, evidences are demonstrating the active role of glia, in particular astroglia, in cognitive processes like learning and memory and, for these reasons, it has been proposed the foundation of a specific field to study these functions because investigations in this area are still limited due to the dominance of the neurocentric perspective.