NEURAL NETWORK

NEURAL NETWORK

Neural network has the following main functions:
1. As a means of communication in the body:
This function is visible from the neural network's ability to receive, maerubah stimuli (stimulus) into an impulse and then distribute throughout the nerve and the nerve ending at the center.
2. As a means of coordination:
All nerve activity that is necessary for coordination owned by the neural network itself.
These two functions are closely related to running a functional alignment for all activities of daily living, so that the individual can adapt itself to the changes happening around him.
Subject of neural networks there are two aspects, namely:
a. Organization of the neural network
b. Morphological neural networks
 
A. NEURAL NETWORK ORGANIZATION
Structural units of a neural network is a form of a unit called NEURON. The unit entity can be either genetic unit, unit morphologic, and trophic unit of the nervous system. Forms of unity (Neuron) consists of cell bodies (cyton / soma) and penjuluran cytoplasm. Penjuluran cytoplasm is often called Neurit (axons) and Dendrite, while part perikaryon cell body around the nucleus. Following that neurons together with neuroglia that act as support cells to form neural tissue. Relations between neurons as an introduction occurs through synaptic impulses. So it is a relationship neuron synapses with other neurons. Neurons conduct impulses toward unity only are known as Dynamic Polarization.
Neuron Doctrine:
1. Each neurons derived from embryonic stem cells that have the neuroblast genetic information to perform its functions.
2. Each neuron is a separate structural unit clearly with another neuron units are in contact with other units.
3. These units form a chain-like cells that constitute the nervous system conduction mechanism.
4. Each neuron is responsible for nutrition, metabolism, and maintenance of its own component parts
Nerve tissue found in the central nervous system such as the cerebrum (the cerebrum), cerebellum (cerebellum), and spinal cord will be discussed further on organological subjects.
B. NEURAL NETWORK MORPHOLOGY
Neurons have many types and yet has the same main hungsi receive stimuli from the environment (interosepsi) and receive stimuli from the outside (exterosepsi). Ability irritability and high conductivity of the cytoplasm is the main support neuron function but very little regeneration capability.
Cells that are closely associated with the survival / functional jaringat Sharh are neuroglia cells. Tues neuroglia role for protection, nutrition, and the structural integrity of the neural network.
CLASSIFICATION NEURON
Neurons have a wide variety of size, shape, number of process of the cell, and the long process of the cell. Morphologic diverse neurons that illustrate the adaptation to the functional changes that occur vary widely.
Neurons can be divided into 2 groups of neurons and neuronal secretory transmission.
A. Neuron Transmission
The bulk of the neurons. These neurons had dendrites, cell body, and an axon. Based on the number of neurons transmitting penjuluran there are several types, among others:
a. True Unipoler neurons: these neurons have only one axon, these types are limited to the developing nervous system. There was also looking penjuluran coming out from the cell body and then just a separation between neurt and dendrites. If penjuluran short and immediately separate the so-called pseudo-unipoler neurons. Type of sensory neurons generally. Axon and dendritnya unite close to the body cells, but the cells were still visible on the body looks a little apart before penjuluran it together. In the retina there are cells that have no axon amacrin, so the neuron is also called a neuron-anaxonik.
b. Bipoler neuron: neuron has a primary dendrites and an axon that lies at the opposite poles of the cell body. Here clearly see two separate penjuluran clear out of the body cells, where it is one as neurit (axon) and the other as dendrites. Examples of these types of neurons found in: retina, ganglion vestibulare, Spinale ganglion, olfactory cells.
c. Multipoler neurons: These neurons have many penjuluran, but are clearly visible only one will serve as a rest as axons and dendrites. This type is most commonly found. In the central nervous system found in limited: pyramidal neurons, Purkinje cells and motor neurons of the spinal ventral cornua.
  
When viewed from penjuluran short term, many types of branched neurons multipoler bit tired again divided into:
(A) neuron Golgi type I: type also called Deiter. This type has many dendrites and a long axon that ends form a complex branching or telodendron called axon terminals. Found in nerve perifir the preganglionic sympathetic and parasympathetic neurons, sympathetic postganglionic neurons.
(B) Golgi type II neuron: neuron has many dendrites and axons sebuh short and ends not far from the cell body. Commonly found in the substantia grisea and not to enter the area substantia alba. Axon terminals called neuropodia. Examples are in: neoron in the cerebral cortex, cortical serebelli, and retina.
Neuron neurosekretorik
Are specific nerve cells which have the ability mensintese, and then transport the object Herring through the next axonnya liberate various substances (hormones) into the blood. The relationship between the vasa blood cells called neurohemal organ. Some cells neurohemal neuropypophyse (hypopise pars posterior) produces oxytocin and antidiuretic hormone (ADH). There was also found on the cell neurohemal hypothalamusyang produces releasing factors (releasing hormone).
 
Morphology of nerve cells:
Forms of nerve cells (perikaryon) generally round, can also polihidral birkisar diameter between 4-150 microns. The point is round and large, relatively little chromatin is located in the nucleus eccentrically so it looks a little pale. Children nucleus (nucleoli) is generally one containing RNA and protein basis, so that nucleoli may be basophils or asidopil used depending on the type of painting
Perikaryon or nerve cell bodies, have called neuroplasma cytoplasm, whereas the axon / dendrite called aksoplasma. Inside there is a plasma cell organelles such as the Golgi apparatus, mitochondria, sentriola, paraplasma (pigment / fat), and neurofibril. There are also grain-butira in it contains a type of protein / hormone called Nissl objects located on the border of the cell body with dendrites or axons but not found in axons. The study further reported that the object is nothing Nissl endoplasmik bitir reticulum with RNA. Nissl bodies in number in the cell bodies varies depending tersebuit activity of nerve cells, for example, the state of fatigue or breaks are few in number and not so much found in the pathological state. Event loss / reduction in Nissl bodies are called Khromatolisis. Khromatolisis is reversible. Variations in Nissl bodies are the main characteristics of various types of neurons. Garanul-granules are (Nissl bodies) are actually grouped RER, free ribosomes and polysoma. Respect of most neurons do not produce extracellular proteins for transport. So with the Nissl bodies whose numbers are changing quite confusing. The results stated that in one day the neurons and fix 1/3 of the total protein and Nissl bodies expected to play a role in the formation of proteins. Kromatolisis process coupled with the increase in ribosomes, RER, and polysoma then the process can also be diangga kromatolisis as the restoration process neuron itself. At the base of the axon in the perikaryaon tercat / visible light because of low electron density, the area is called the axon-Hillock
Based on the functional classification Bodian neurons can be divided into 3 zones:
1. Dendritic zone: is the area of ​​neurons that is the subject of the stimulus excitation and inhibition. Included in this zone are: dendrites, cell bodies and axons surface segments. Impulses coming to this zone may cause or do not cause the action potential and the response is graded.
2. Axonik Zone: arborisasi segment is covering nerve endings. This area is part of conduction that is all or none
3. Telodendritik Zone: is a terminal modifications include allowing the transfer of electrically or chemically to the next neuron or to an effector organ. Responses are graded.
 
Dendrites
Dendrites serve to expand the surface of neurons, similar to tree branches. Dendrites are usually shorter than the axon, branching in kontunyu to smallest. The surface of dendrites and cell bodies or gemmula spina tertutupoleh which is synaps relationship with axon terminals of other nerve cells. Fill in the cytoplasm of cells with cytoplasmic bodies. Nissl bodies confined to the proximal part of the dendrites.
AXON
Axon or axis cylinders arising from the axon Hillock in perikarion. This single process of the smooth surface and a diameter of constant size. Before ending the first effector branches forming telodendron. Plasma membrane of axons called axolemma. Beginning segment where the advent of the cell body is beginning myelinisasi place, other than that this place has exitasi lower threshold than in dendrites and cell bodies. Nodes of Ranvier found in several places along the axon bermyelin and is discontinuous from the myelin sheath .. In place disebungi axons by glial cell cytoplasmic processus. On the Nodes of Ranvier axons thicken. Nodes of Ranvier are functionally saltatorik impulse conduction meloncatnya ie a depolarization wave from one node to the next node. Organelles such as mitochondria, neurotubulus, neurofilament, SER, and Nissl bodies are not found in axons and in axon Hillock. Because of the long process of the transportation problem, there will be an impulse or other substances. The flow of material there are 2 kinds of material flowing from the cell body called somatopugal (retrograde) and materian flow into the cell body called somatopetal (anterograde).
Flow somatopugal there are 2 kinds: flow axoplasmik axoplasmik slow and fast flow. Most of the material in axoplasma moving slowly with a speed of 0.5 - 5 mm / day, it is necessary to transport materials besdar for maintenance, replacement of old organelles that sud ah or to repair axon. But there is also material flows at speeds 10-200 mm / day which is a fast flow. This rapid flow using aid as a tool neurotubulus organelle transport. The material is transported quickly used for the ongoing functions of synaps axons. Relative properties of the cell body that responds to changes in the flow of axons occurs also somatopetal (anterograde)
TRANSFER INFORMATION
Neurons are modified to generate and conducts information throughout the body in the form of electrical message. Equally important is the ability of neurons to transfer information to and effector organs or neurons.
 
Information transfer mechanism occurs in 2 ways:
1. The mechanism of transfer of electronic transmission
2. Electrochemical transfer mechanism
ELECTRONIC TRANSMISSION MECHANISM
Electronic transmission of nerve tissue occurs in a specific place called efapses elektrotonic junctions also called electronic sinapses. In other tissues such NEXI called Gap junctions. Space formed is very narrow so there is no difference in ion concentration between the two cells. Stimulus that through polarization efapses should not have to drain the material from one cell to another, so that electricity can be run quickly.
Electrochemical Mechanism
Sinapses is where the electrochemical transmissions occur and are more common than efapses. Electrical activity in the presynaptic membrane of nerve cells cause the release of neurotransmitter substances across the intercellular space and linking the receptors on the post-synaptic cell membrane. Unity between neurotransmitter cells with the receptor will lead to changes that can be exitasi or inhibition. Diffusion process of liberation and unity both transmitter substance at the receptor resulted terhabat transmission time. These barriers are called Barriers sinapses.
End of the axon is presynaptic membrane elements, while the effector organ is postsinaptik membrane. Both membranes are separated by intercellular space (the synaptic cleft / synaptic cleft) in width 6-20 nm and contains electron dense material and fine filaments. In the field there postsinaptik membrane thickening due to the filament, and the thickening is called subsynaptic web. At the end there is a presynaptic mitochondria, neurofilament, neurotubulus, and synaptic vesicles. Dense cytoplasmic membrane can be found on pre-and postsinaptik, sometimes it can also be found only on one of them. Unlike the chemical sinapses efapses the polar (one-way flow) is sesalu from membrane to membrane postsinaptik presinapstik.
Presynaptic section extends the cylinder axis to form formations such as light bulbs or buttons. Expansion at the end of axons called boutons terminauuk while the expansion along the cylinder axis called boutons passage. Both kinds of extensions can be found in the axons of nerve fibers was bermyelin or at nodes of Ranvier bermyelin nerve fibers.
End of the axon can form sinapses other neurons with different parts, namely:
1. axo-somatic
2. axo-dendritic
3 axo-axonal
4. dendro-dendritic
5. somato-dendritic
6. somato-somatic
Sinapses formed between nerve cells to skeletal muscle cells called neuro-muscular-Junctura.
 
Neuroglia
Connective tissue of the body to form the main frame in most of the organs. Framework of these networks is not only as an advocate but also a means where the components of vascular spread to all parts of parenchim. Model of close relationships and dependencies are the structural properties of the nervous system perifir. Such relationships are not menojol the central nervous system. Neuroglia is the ectoderm-derived epithelium has a uniquely modified. Epithelium is dependent on the bonding network but separate from it. Central nervous system derived from the development of two kinds of cells: one group of cells to form neurons growing form complex geometric buildings and other groups that develop between the neurons. This second group of cells that dikenel with neuroglia (glial cells). Neuroglia function or stroma forming the framework underpinning the central nervous system. Moreover neuroglia neurons also form adhesive that binds neurons together. Besides, as an advocate also has the function as protection, nutrition supplies, and other functions-Functions for the integrity of neurons. Neuroglia are also present in the nervous system perifir.
Based on its size, there are two macamneuroglia: namely makroglia and microglia.
Makroglia are classified as:
1. oligodendrosit
2. astrosis
3. ependima
4. amfisit
5. Schwann cells
6. cell Muler
Microglia are classified as:
1. mikrogliosit
In addition based on the shape neuroglia cell size can also be classified based on relationship with the central nervous system nervous system perifir namely:
Gliasentral: including the
1. oligodendrogliosit
2. astrocytes
3. ependima
4. Muller cells
5. mikrogliosit
Gliaperifir:
1. ampisit
2. Schwann cells
With routine staining (HE) and cell bodies of neuroglia cells prosessus not so clearly visible. Gliaperifir hymn identified based on the view relation to elements of the nervous system perifir.
Neuropil is a term used to describe a complex arrangement of similar nets contained in the cells of the central nervous system. In the neuropil are processus cells (axons and dendrites) and substantia grissea neuroglia elements.
Oligodendrogliosit
Oligodendrogliosit is the largest number of neuroglia. Specific characteristics: small nuclei, round or oval shape, containing a moderate amount of heterochromatin. Nucleus varies from small to large and pale and dark. In general, the nucleus is smaller and more rounded than the nuclei of astrocytes. Less dense cytoplasm, processus little, these cells are sandwiched between processus cells and neuronal cell bodies. Also has close ties with the blood capillaries. Oligodendroliosit can perineuronal position, perivaskuler, or intervasikuler. Oligodendroliosit perineurel has a nutritional function. In the cat brain is approximately 90% of the surface covered by the cell bodies of these cells.
Oligodendrogliosit role in the process processus melenisasi cells in the central nervous system. This function affects the speed of the production along processus nerve cells.
Astrocytes
In a number of central nervous system no. 2 after oligodendroliosit. There are 2 types of astrocytes and astrocytes fibrosan protoplasmik. Which protoplasmik protoplasm richer than others. Fibrous astrocytes are more common in the protoplasmik substansialba were more commonly found in the substantia grisea. Both have a large nucleus, round or oval usually very pale. Finely granular chromatin clumping sometimes seem peripheral.
Astrocytes important as the structural underpinning of the brain and spinal cord. These cells also play a role in the repair and scar formation in the central nervous system. Astrocytes may experience hipertrodi, hiperprasi and is fogositik. Astrocytes function as an insulator surface receptors of nerve cells. Classically these cells serve as a barrier / brain barrier and the blood relations.
Mikrogliosit
Largest in the central nervous system, not dense cytoplasm, the nucleus is small and dark. Nuclei can be round, has indents or irregularly shaped. Processai many cells. These cells are included in the system macrophages derived from bone marrow promonosit tulsng nerah. But not all researchers agree. Mikrogliosit fogositosis that can only do a little damage. If the damage is large, then fogositik cells migrate from the blood to help mikrogliosit vasa.
Tues Muller
Tues neugrolia Muller is a specific element, found in the retina of the eye.
Ependima
Neuroglia is an element that limits neural canal. These cells limit the spinal cord neural canal and fourth ventricles are in the brain. This layer has a striking picture of the places chorioideus plexus because the cells are modified far enough. In emberyo ependima shaped cells kolumner kuboid or low. Tues epindema have large nuclei and pale, nekleoli one or more. In adults, basal edge is separated from the neural tissue by basement membrane. In young animals, so complex are modified basal processus sitoplasmatiknya dam may extend to the neural network.
Epindema cell function varies, among others, to the formation of cerebro-spinal fluid. The process of formation of cerebrospinal fluid is not confined to cells in the plexus choriadius epindima but also occur in scattered areas in the brain ventricles. Tues ependima the ciliated serves to move the cerebrospinal fluid in the ventricular system of the brain. Nerve endings are sensory ependima layer. Cerebrospinal fluid produced by ependima cells may contribute to the transport of hormones. Tanycyt is specific cells found in layers ependima, mainly found in the walls ventrikeltertius. These cells have basal processus long, not branched and extends to areas subependima ended capillaries in the area, these cells may not only structural function, they may contribute to the transport and / or secretory activity.
Organ subependima may serve to generate replacement cells neuroglia throughout the life of the organism.
Amfisit
Amfisit (satellite cells, cell capsules) is a peripheral glial cells that surround neurons neuroglia ganglia. These cells limit prikaryon ganglia, may proceed to the sheath of Schwann himself. Amfisit may have a close relationship with oligodendrogliosit.
Schwann cells
Schwann cells of peripheral glia associated with nerve fibers. They wrapped fibers and play a role in the formation of myelin. These cells may have a close relationship with oligodendrogliosit.
The relationship between neurons and neuroglia
Through the development of central nervous system neurons have a close relationship with the central neuroglia cells. Oligodendrogliasit form a unique relationship with neurons, namely the formation of the myelin sheath of nerve cells in the processus central nervous system. Processus nerve cells and some neurons (the ganglion cells) present in the peripheral nervous system and enveloped neuroglia elements which are related to the cell body and processus cells similar to those described in the central nervous system.
The structure of connections between neurons with varying neuroglia cells. Amfisit ganglion cells form a single cell sheath around the cell. No nerve fibers sheathed bermyelin Schwann cell plasmalemma invagination. Bermyelin nerve fibers are also covered by invagination Schwann cells that form the myelin sheath. Myelin sheath composed of folds memberan.
Sheath ganglion cells. Ganglion cells are nerve cells that are part of an peripheral nervous system. A collection of nerve cell bodies called ganglia. The cell body is covered by a layer of cells called amfisit. Although amfisit usually a continuous sheath ganglion as in Ganglian radix dorsalis, the autonomic Ganglian be incomplete. The sheath is not confined to the cell body but can extend into the dendrites and axons beginning part of the segment. Amfisit end at the Schwann cells begin to appear.
Not Bermyelin nerve fibers. Tues Schann processus formed sheath of nerve cells. Not Bermyelin nerve fibers or fiber Remak, a tiny fibers that not only enveloped bermyelin or one layer of myelin. These fibers were enveloped by invagination elongated Schwann cells. But the fibers are not in the cytoplasm, but only wrapped by Schwann cell plasmalemma. Such sheaths are called Schwann sheath or sheath neurolemma. Schwann cells also called neurolemma cells. Plasmalemma Schwann cells that wrap around the cylinder axis called mesaxon. A Schwann cells can form a sheath for a lot of nerve fibers. Because of a Schwann cell sheath fibers can only be formed in a limited range, then the sheath is formed of a row neorolemma Schwann cells are connected in a row. Located in the basal lamina neurolemma peripheral sheath, Schwann cells wrap and separated from the connective tissue.
Schwann cell function belun clear right here. But perhaps for the repair process. Nerves do not bermyelin small, small conduction velocity.
Nerve fibers Bermyelin
This is the big nerve fibers and has a top speed of conduction. Function here similar to myelin insulation on electrical wires. Oligodendrogliosit and Schwann cells responsible for myelin formation. Although the means and the end product is slightly different, but the end result showed that nerve fibers wrapped in myelin sheath.
Axis cylinder or nerve cell has axio processus plasma and bounded by the cell membrane, called the axolemma. Room near the axis slinder filled with myelin sheath. In the painting routine, loss of lipid membrane would change the picture rolls. What remains is called the myelin sheath component nonlipida neurokeratin, appear as spokes of a wheel. In Schwann cells are peripheral neurokeratin. The cell has a large nucleus, vesicles with chromatin clumps in the periphery. Schwann cell cytoplasm which limits the myelin sheath called neurolemma or Schwann.
A Schwann cell envelops not the entire length of nerve fibers, but the nerve fibers sheathed by Schwann cells were serially. The place is called a node of Ranvier junction. This node appears as a narrow section that have no myelin, but still enveloping Schwann cell processus axolemma. Axis cylinder is never interrupted in rodus.
Electron microscopic picture better explain the relationship between the myelin sheath, axis cylinders and neuroglia elements. Myelin sheath is formed from a continuous roll formed by the processus sitoplasmatik neuroglia cells. Internal Mesaxon processus formed by Schwann cells are confronted with processus nerve cells. Internal Mesaxon is located on the same picture of peripheral myelin. Outer myelin sheath wrapped Schwann cell cytoplasm that acts on the myelinisasi. A limiting basal lamina of Schwann cells and separated from the surrounding connective tissue.
Myelinasi
Process myelinasi nerve fibers of the peripheral nervous system as a result of the close relationship between nerve fibers and Schwann cells. Myelinasi on pust nervous system nerve fibers occurs because of the close relationship between nerve fibers and oligodendrogliasit.
Many nerve fibers bermyelin not covered by a Schwann cell. In the process of the peripheral nerves myelinasi then an invagination along the nerve fibers to fill Schwann cells. Penjuluran shaped like a tongue of Schwann cells wrap around the cylinder axis. Furthermore, the cytoplasm of penjuluran disappear, so that the plasma membrane into close together. Myelinasi degree or myelin sheath thickness depends on the number of turns during the process myelinasi. A Schwann cells are responsible for the myelinasi nerve fibers between the nodes of Ranvier to the next.
There is little difference between the myelinasi in peripheral and central. Connective tissue is not commonly found in the central nervous system. Bermyelin adjacent nerve fibers is not restricted to the basal lamina. Oligodendrogliasit cell bodies may form the myelin sheath but associated with myelin through processus cells. A sheath for oligodendrogliasit can form more than one nerve cell, or envelop more than one internodal region.
Tues neuroglia is important to maintain the integrity of the myelin sheath in addition to the remyelinasi after demyelinasi after the attack due to damage or disease.