What is the connection between glial cells and neurons?
Hello, both glial cells and neurons originate from the ectoderm neuroepithelial tissue of the blastodisc (microglia may originate from the mesoderm), and the glial blasts develop into macroglial cells and choroid plexus epithelial cells, surrounding Part of the neuroepithelial cells on the luminal surface of the neural tube differentiate into ependymal and choroid plexus epithelial cells, neuroblasts develop into neurons, and the neural crest differentiates into glial cells of the peripheral nervous system.
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What is the Difference Between Neurons and Glial Cells?
Glial cells are one of the two major cells that make up the nervous system, and together with neurons, they form a good copy of the nervous system .
Glial cells do not conduct nerve impulses, but they support, protect, separate, isolate, transport and nourish neurons, and are also an important part of the blood-brain barrier, which can be understood as the logistics support system of the nervous system.
Glial cells can be divided into four types: astrocytes, oligodendrocytes, ependymal cells, and microglia. Once the first three types of cells grow uncontrollably, they can form the correspondingly named cells. Tumors such as astrocytoma, oligodendroglioma, and ependymoma.
Microglia are immune cells in the nervous system that do not form tumors by themselves.
Classification: (1) According to the number of protrusions from the cell body, neurons can be divided into 3 types from the morphology: 1. Pseudo-unipolar neurons: the cell body is approximately round, with a protrusion, and is divided into two not far from the cell body. One branch of dendrites distributes to the skin, muscles or internal organs, and the other axon enters the spinal cord or brain.
2. Bipolar neuron: The cell body is approximately fusiform, with one dendrite and one axon, distributed in the retina and vestibular ganglion. 3. Multipolar neurons: The cell body is polygonal, with an axon and many dendrites, and is the most widely distributed. Neurons in the gray matter of the brain and spinal cord are generally of this type.
on neurons and glial cells
neurons nerve fibers glial cells nerve endings
Definition of Nerve Cells Nerve cells are the structural and functional units of the nervous system of higher animals, also known as neurons.
The nervous system contains a large number of neurons. It is estimated that there are about 100 billion neurons in the human central nervous system, and there are about 14 billion neurons in the cerebral cortex alone. The basic structure of neurons 1 . The basic structure of a neuron: it can be divided into two parts: the cell body and the process.
The cell body includes the cell membrane, cytoplasm and nucleus; the protrusions are issued from the cell body and are divided into dendrites and axons.
There are many dendrites, which are thick and short, repeatedly branching, and gradually become thinner; generally there is only one axon, which is slender and uniform, with fewer branches in the middle, and many branches at the end. The terminal part of each branch is enlarged and spherical, called axon contact body. Where the axon arises, the cell body often has a conical bulge called the axon mound.
After the axon emanates from the axon mound, the first segment without myelin sheath is called the initial segment. Since the density of voltage-gated sodium channels in the initial cell membrane is the largest, the threshold for generating action potentials is the lowest, that is, the excitability is the highest, so action potentials are often generated first.
The axon acquires the myelin sheath after leaving the cell body some distance away and becomes a nerve fiber.
The function of neurons 2. The function of neurons: the basic function of neurons is to realize information exchange by receiving, integrating, transmitting and outputting information. Sample exchange output.
The produced samples light up the sensory perception through the connection path to produce consciousness.
The functional division of neurons, whether they are motor neurons, sensory neurons or interneurons, can be divided into: 1) Input (feeling) area In terms of a motor neuron, the receptors on the cell body or dendritic membrane are An input region that receives incoming information and that generates postsynaptic potentials (local potentials).
2) The beginning of the integration (triggering impulse) area belongs to the integration area or triggering impulse area, where numerous post-synaptic potentials are summed up, and action potentials are first generated here when the threshold potential is reached.
3) The axon in the impulse conduction area belongs to the conduction impulse area, and the action potential is transmitted to the innervated target organ in a non-attenuating manner. 4) The synaptosome at the end of the axon in the output (secretion) area is the information output area, where neurotransmitters are released through exocytosis.
There are also a large number of glial cells (neuroglia) in the nervous system (tens of times that of neurons), such as astrocytes, oligodendrocytes, microglia in the central nervous system and peripheral nervous system Schwann cells in et al.
Due to the lack of Na+ channels, all kinds of glial cells cannot generate action potentials.
The main functions of glial cells are as follows: ① Supporting the process of astrocytes interweaving into a network, supporting the cell bodies and fibers of neurons; ② Insulating oligodendrocytes and Schwann cells to form the central and peripheral nerve fibers respectively Myelin sheath, so that the activities between nerve fibers basically do not interfere with each other; ③ Barrier function Some of the protruding ends of astrocytes are enlarged and terminate on the surface of capillaries (perivascular feet), covering 85% of the surface area of capillaries , is an important part of the blood-brain barrier; ④ trophic role astrocytes can produce neurotrophic factors (neurotrophic factors, NTFs) to maintain the growth, development and survival of neurons; ⑤ repair and regeneration of microglia Cells can transform into macrophages, which can remove neurons and their cell fragments degenerated due to aging and disease through phagocytosis; astrocytes can proliferate and multiply to fill the defects left by neurons after death, but if the hyperplasia is excessive , can become the cause of brain tumors; ⑥ Maintain K+ balance around neurons When neurons are excited, K+ will flow out, and astrocytes will pump K+ into the cell through the Na+-K+ pump on the cell membrane, and then pass through the cell The interchannel (gap junction) quickly disperses K+ to other glial cells, so that the K+ around neurons will not increase excessively and interfere with neuron activity; The glial cells of the ganglion can take up neurotransmitters, so it is related to the maintenance of neurotransmitter concentration and synaptic transmission.
Neurons and nerve fibers There are a large number of neurons in the nervous system, and the connection between neurons is only in contact with each other, but there is no continuity of protoplasm. Typical neuron dendrites are many, short, and multi-branched; axons are often very long, and they begin to obtain myelin sheath after leaving the cell body for a certain distance and become nerve fibers.
Nerve fibers can exert two effects on the tissues they innervate: on the one hand, the presynaptic membrane releases special neurotransmitters when the excitatory impulse reaches the terminal, and then acts on the postsynaptic membrane, thereby changing the innervated neurons. Functional activities of tissues, this effect is called functional effect; on the other hand, nerves can often release certain substances through the end, continuously adjust the internal metabolic activities of the dominated tissues, and affect its persistent structure, biochemical and physiological functions. Changes, which have nothing to do with nerve impulses, are called trophic effects.
Issues related to nerve impulses have been discussed in Chapter Four (see Chapter Four, Basic Physiological Functions of the Human Body for details). Only the trophic effects of nerves are discussed here. The study of neurotrophic effects is mainly carried out on motor nerves.
Experiments have shown that after the motor nerve is cut off, the synthesis of glycogen in the muscle slows down, the decomposition of protein accelerates, and the muscle gradually shrinks; if the nerve is sutured to regenerate, the muscle changes can be restored. At present, it is believed that the trophic effect is completed due to the frequent release of certain nutrient substances from the extremities, which act on the dominated tissues.
Nutrients are synthesized by the neuron cell body, and then transported to the nerve terminal by the axoplasmic flow for release.
Axoplasmic flow has nothing to do with nerve impulse conduction, because continuous use of local anesthetics to block the conduction of nerve impulses does not stop axoplasmic flow, and the muscles innervated by it will not undergo metabolic changes and atrophy.
The axoplasm is always flowing, and the flow is bidirectional: on the one hand, part of the axoplasm flows from the cell body to the axon terminal, and on the other hand, part of the axoplasm flows from the terminal to the cell body in reverse. 2. The way of interaction between neurons (1) Synaptic transmission The nervous system is composed of a large number of neurons.
There is no protoplasmic connection between these neurons in structure, only contact with each other, and the contact parts are called synapses. Due to the different contact parts, synapses can be mainly divided into three types: ① axon-cell body synapse; ② axon-dendritic synapse; ③ axon-axon synapse (Figure 11-1).
The axon terminal of a neuron repeatedly branches, and the end expands into a cup-shaped or spherical shape, called a synaptosome, which contacts the cell body or protrusion of the postsynaptic neuron.
One presynaptic neuron can form synapses with many postsynaptic neurons, and one postsynaptic neuron can also form synapses with the axon terminals of many presynaptic neurons. The cell body and dendrite surface of a motor neuron in the anterior horn of the spinal cord are covered by about 1800 synaptosomes (Figure 11-2).
Observed under the electron microscope, there are two membranes at the synapse, which are called the presynaptic membrane and the postsynaptic membrane, and the synaptic cleft is between the two membranes. Therefore, a synapse consists of three parts: the presynaptic membrane, the synaptic cleft, and the postsynaptic membrane. The thickness of the front film and the back film is generally only about 7nm, and the gap is about 20nm.
The axoplasm close to the anterior membrane contains mitochondria and synaptic vesicles with a diameter of 30-60nm, which contain chemical transmitters.
On the inner side of the pre-membrane, there are dense protrusions and grid-formed vesicle barriers, and the gaps just accommodate a synaptic vesicle, which may have the function of guiding the contact between the synaptic vesicle and the pre-membrane, and promoting the internalization of the synaptic vesicle. Transmitter release.
When the impulse from the pre-synaptic neuron reaches the synaptosome, the transmitter in the vesicle is released from the pre-synaptic membrane, enters the synaptic cleft, and acts on the post-synaptic membrane; if this effect is large enough, It can cause excitatory or inhibitory responses of postsynaptic neurons.
It has also been observed that there is an alternative mode of synaptic transmission of monoamine transmitters in neurons. The axon terminals of such neurons have many branches, and there are a large number of nodular varicose bodies on the branches. The varicose body contains a large number of vesicles (Figure 11-3), which are the sites of transmitter release.
However, varicosities do not make direct contact with postsynaptic neurons or effector cells, but lie in their vicinity. When a nerve impulse reaches the varicose body, the transmitter is released from the varicose body and diffuses to receptors on the postsynaptic cell membrane, producing a transmission effect.
This mode of transmission exists both in the central nervous system and on postganglionic sympathetic fibers. (2) Gap junctions The information connection between neurons in higher animals can also be accomplished through gap junctions. For example, stellate cells in the cerebral cortex and basket cells in the cerebellar cortex have gap junctions.
Local currents can pass through gap junctions, and when one side of the membrane is depolarized, the other side of the membrane can also be depolarized due to electrotonicity. Therefore, gap junctions are also called electrical synapses. References:
Neurons and glial cells are functionally different
1. CNS: mainly includes astrocytes (fibrous astrocytes, protoplasmic astrocytes), oligodendrocytes, microglia, Ependymal cells (ependymal cells) and peritubular cells, choroid plexus epithelial cells, Bergmann's glial cells, Müller cells, pituitary cells, and stretch cells.
2. Surrounding: Schwann cells (Schwann cells), satellite cells (satellite cells).
Both glial cells and neurons originate from the ectoderm neuroepithelium of the blastodisc (microglia may originate from the mesoderm), in which glial blasts develop into macroglia and choroid plexus epithelial cells, surrounding the neural lumen Part of the neuroepithelial cells on the surface differentiate into ependymal and choroid plexus epithelial cells, and neuroblasts develop into neurons; the neural crest differentiates into glial cells of the peripheral nervous system.
Astrocytes are the largest glial cells, with a cell body diameter of 3 to 5 microns, a spherical nucleus often located in the center, and lightly stained. It has many long processes, one or several of which extend to the adjacent capillaries, and the ends of the processes are enlarged to form vascular foot processes, and a layer of glial membrane is formed around the endothelial basement membrane of the blood vessels.
Some astrocyte processes are also attached to the submembrane of the pia mater and ependyma of the brain and spinal cord, separating the pia mater, ependyma and neurons. There are two types of astrocytes: protoplasmic and fibrous.
Protoplasmic astrocytes are mostly found in gray matter. The processes are thicker and more branched. They are in the form of thin plates and surround the parts of neuron cell bodies and dendrites that are not covered by synapses. There is a small gap between them and neuron cells.
The processes of fibrous astrocytes are long and smooth, without too many branches, and there are many fibril-like substances in the cytoplasm of the cell body and processes, integrated into bundles of different sizes.
Electron microscope observations show that the perinuclear cytoplasm and large protrusions of protoplasmic and fibrous astrocytes contain the same organelles, as well as obvious glycogen granules and cytoplasmic fibrils, etc., indicating that the two types may belong to the same type of glial cell.
Some people think that astrocytes can proliferate through mitosis and amitosis due to injury or stimulation under abnormal conditions, but astrocytes near the damaged part of the cerebral cortex of mice do not take up 3H-labeled thymidine, so they still Cell proliferation could not be confirmed.
Oligodendrocytes are smaller than astrocytes, with a diameter of 1 to 3 microns, and their processes are less than other glial cells, shorter and beaded, with no vascular feet, no fibers in the cytoplasm, but more than astrocytes of mitochondria. Oligodendrocytes are present in both gray and white matter, and in gray matter immediately surrounding neurons are called satellite cells.
The human central nervous system has the highest number of oligodendrocytes per neuron. Satellite cells of neurons increase in number in response to injury and can engulf their own products of myelin degeneration. Oligodendrocytes appear in rows between myelinated fibers in the white matter.
The myelin sheath of central nervous tissue is formed by the processes of oligodendrocytes and, therefore, functions in the same way as Schwann cells of peripheral nerves. A single oligodendrocyte can form the sheath (up to 20) of the multipolar interfibrillary junction with its different processes.
Oligodendrocytes have round and small nuclei, dense chromatin, and a cytoplasm with high electron density, containing mitochondria, ribosomes, and microtubules, which make them identifiable in electron microscopy images. Periodic vigorous movements of oligodendrocytes were seen in tissue culture. The microglial cells are small and dense, elongated or oval.
The chromatin in the nucleus is very dense, and the nucleus is also elongated along with the long axis of the cell body. Microglia are characteristic in hematoxylin-eosin-stained sections; processes are short and densely covered with numerous twigs resembling spines.
Although the number of microglial cells is not large, they are present in gray matter and white matter, and the number in gray matter is 5 times more than that in white matter. The number of microglia in hippocampus, olfactory lobe and basal ganglia is more more, and least in the brainstem and cerebellum.
Some phagocytic microglia were apparently derived from monocyte stem cells in hematopoiesis rather than neural origin, and many invading phagocytic cells emerged after injury. Under normal circumstances, astrocytes have the function of phagocytosis to remove cell debris.
Difference Between Neurons and Glial Cells Compare the Difference Between Similar Terms
Nerves are nerve cells, which have axons and dendrites. Nerve fibers are composed of axons or dendrites, myelin sheath and nerve membrane. Among them, the processes of neurons are slender and long like fibers, so they are called nerve fibers. Glial cells also have cell processes like nerve cells, but their cytoplasmic processes do not distinguish between dendrites and axons.
Unlike nerve cells, it has the ability to divide and proliferate for life. The terminal part of the nerve fiber, which is distributed in various organs and tissues. According to their different functions, they are divided into sensory nerve endings and motor nerve endings.
What is the Difference Between Nerve Cells and Glial Cells?
Nervous tissue is the main component of the nervous system, including nerve cells and glial. Nerve cells are the structural and functional units of the nervous system, also known as neurons. They have the functions of receiving stimuli, transmitting impulses and integrating information. Some neurons also have endocrine functions.
Glial cells, also known as glial cells, are about 10 to 50 times the number of neurons. They are mainly distributed between neurons and do not have the function of conducting impulses. Instead, they support, nourish, insulate and protect neurons. .