"guided the entire time by the regeneration tube. Nerve regeneration is very slow and can take up to several months to complete. While this process does repair some nerves, there will still be some functional deficit as the repairs are not perfect. A nerve conveys information in the form of electrochemical impulses (as nerve impulses known as action potentials) carried by the individual neurons that make up the nerve. These impulses are extremely fast, with some myelinated neurons conducting at speeds up to 120 m/s. The impulses travel from one neuron to another by crossing a synapse, the message is"
"between two cells in close apposition to one another. In a synapse, the neuron that sends the signal is the presynaptic neuron and the target cell receives that signal is the postsynaptic neuron or cell. Synapses can be either electrical or chemical. Electrical synapses are characterized by the formation of gap junctions that allow ions and other organic compound to instantaneously pass from one cell to another. Chemical synapses are characterized by the presynaptic release of neurotransmitters that diffuse across a synaptic cleft to bind with postsynaptic receptors. A neurotransmitter is a chemical messenger that is synthesized within neurons themselves"
"Active zone The active zone or synaptic active zone is a term first used by Couteaux and Pecot-Dechavassinein in 1970 to define the site of neurotransmitter release. Two neurons make near contact through structures called synapses allowing them to communicate with each other. As shown in the adjacent diagram, a synapse consists of the presynaptic bouton of one neuron which stores vesicles containing neurotransmitter (uppermost in the picture), and a second, postsynaptic neuron which bears receptors for the neurotransmitter (at the bottom), together with a gap between the two called the synaptic cleft (with synaptic adhesion molecules, SAMs, holding the"
"synapse with the dendrites of the same neuron, resulting in an autapse. At a synapse, the membrane of the axon closely adjoins the membrane of the target cell, and special molecular structures serve to transmit electrical or electrochemical signals across the gap. Some synaptic junctions appear along the length of an axon as it extends—these are called ""en passant"" (""in passing"") synapses and can be in the hundreds or even the thousands along one axon. Other synapses appear as terminals at the ends of axonal branches. A single axon, with all its branches taken together, can innervate multiple parts of"
"control system. They were located in the abdominal region. Synapses are known as gaps between neurons which facilitate the spread of a message via neurotransmitters that may excite or depress the subsequent neuron through a complex cascade of electrochemical events. For the interneurons exhibiting one-way signaling, they would receive an excitatory stimulus, experimentally, and the post-synaptic cell was given an inhibitory signal. The interaction between the two cells was modulatory in which the pre-synaptic cell with the initial excitatory signal would mediate the postsynaptic cell even after being inhibited. Signal amplitude was used to determine the effects of the modulation"
"soma and dendrites; signals to other neurons are transmitted by the axon. A typical synapse, then, is a contact between the axon of one neuron and a dendrite or soma of another. Synaptic signals may be excitatory or inhibitory. If the net excitation received by a neuron over a short period of time is large enough, the neuron generates a brief pulse called an action potential, which originates at the soma and propagates rapidly along the axon, activating synapses onto other neurons as it goes. Many neurons fit the foregoing schema in every respect, but there are also exceptions to"
"a synapse, the plasma membrane of the signal-passing neuron (the ""presynaptic"" neuron) comes into close apposition with the membrane of the target (""postsynaptic"") cell. Both the presynaptic and postsynaptic sites contain extensive arrays of a molecular machinery that link the two membranes together and carry out the signaling process. In many synapses, the presynaptic part is located on an axon and the postsynaptic part is located on a dendrite or soma. Astrocytes also exchange information with the synaptic neurons, responding to synaptic activity and, in turn, regulating neurotransmission. Synapses (at least chemical synapses) are stabilized in position by synaptic adhesion"
"called a synapse, across which impulses are sent. The axon terminal, and the neuron from which it comes, is sometimes referred to as the ""presynaptic"" neuron. Neurotransmitters are packaged into synaptic vesicles that cluster beneath the axon terminal membrane on the presynaptic side of a synapse. The axonal terminals are specialized to release the neurotransmitters of the presynaptic cell. The terminals release transmitter substances into a gap called the synaptic cleft between the terminals and the dendrites of the next neuron. The information is received by the dendrite receptors of the postsynaptic cell that are connected to it. Neurons don't"
"cells, that relay electrical signals through the brain and body. A nerve cell receives signals from other nerve cells through tree-branch-like extensions called dendrites and passes signals on through a long extension called an axon (or nerve fiber). Synapses are places where one cell's axon passes information to another cell's dendrite by sending chemicals called neurotransmitters across a small gap called a synaptic cleft. Synapses occur in various locations, including ganglia (singular: ganglion), which are masses of nerve cell bodies. Preganglionic nerve cells in the sympathetic nervous system (all of which come from the lateral grey column), use the neurotransmitter"
"both tonically and phasically in response to the needs of the neural pathways. Neural pathway A neural pathway is the connection formed by axons that project from neurons to make synapses onto neurons in another location, to enable a signal to be sent from one region of the nervous system to another. Neurons are connected by a single axon, or by a bundle of axons known as a nerve tract, or fasciculus. Shorter neural pathways are found within grey matter in the brain, whereas longer projections, made up of myelinated axons, constitute white matter. In the hippocampus there are neural"
"synapse, the cell that sends signals is called presynaptic, and the cell that receives signals is called postsynaptic. Both the presynaptic and postsynaptic areas are full of molecular machinery that carries out the signalling process. The presynaptic area contains large numbers of tiny spherical vessels called synaptic vesicles, packed with neurotransmitter chemicals. When the presynaptic terminal is electrically stimulated, an array of molecules embedded in the membrane are activated, and cause the contents of the vesicles to be released into the narrow space between the presynaptic and postsynaptic membranes, called the synaptic cleft. The neurotransmitter then binds to receptors embedded"
"over which information is transmitted from one part of the neuron (e.g., the cell body) to the terminal regions of the neuron"". The third important piece of a neuron is the synapse. ""The synapse is the terminal region of the axon this is where one neuron forms a connection with another and conveys information through the process of synaptic transmission"". Neural networks like the ones simulated with GENESIS software can quickly become highly complex and difficult to understand. ""Just a few interconnected neurons (a microcircuit) can perform sophisticated tasks such as mediate reflexes, process sensory information, generate locomotion and mediate"
"Neural pathway A neural pathway is the connection formed by axons that project from neurons to make synapses onto neurons in another location, to enable a signal to be sent from one region of the nervous system to another. Neurons are connected by a single axon, or by a bundle of axons known as a nerve tract, or fasciculus. Shorter neural pathways are found within grey matter in the brain, whereas longer projections, made up of myelinated axons, constitute white matter. In the hippocampus there are neural pathways involved in its circuitry including the perforant pathway, that provides a connectional"
"the two cells' cytoplasm. Thus when the membrane potential of one cell changes, ions may move through from one cell to the next, carrying positive charge with them and depolarizing the postsynaptic cell. Gap junction funnels are composed of two hemi-channels called connexons in vertebrates, one contributed by each cell at the synapse. Connexons are formed by six 7.5 nm long, four-pass membrane-spanning protein subunits called connexins, which may be identical or slightly different from one another. An autapse is a electrical (or chemical) synapse formed when the axon of one neuron synapses with its own dendrites. The simplicity of"
"of neurotransmitters may influence the postsynaptic neuron in either an inhibitory or excitatory way. The binding of neurotransmitters to receptors in the postsynaptic neuron can trigger either short term changes, such as changes in the membrane potential called postsynaptic potentials, or longer term changes by the activation of signaling cascades. Neurons form complex biological neural networks through which nerve impulses (action potentials) travel. Neurons do not touch each other (except in the case of an electrical synapse through a gap junction); instead, neurons interact at close contact points called synapses. A neuron transports its information by way of an action"
"good term that emphasized a union between two ""separate"" elements, and the actual term ""synapse"" was suggested by the English classical scholar Arthur Woollgar Verrall, a friend of Michael Foster. Some authors generalize the concept of the synapse to include the communication from a neuron to any other cell type, such as to a motor cell, although such non-neuronal contacts may be referred to as junctions (a historically older term). Synapses are essential to neuronal function: neurons are cells that are specialized to pass signals to individual target cells, and synapses are the means by which they do so. At"
"touch each other, but communicate across the synapse. The neurotransmitter molecule packages (vesicles) are created within the neuron, then travel down the axon to the distal axon terminal where they sit ""docked"". Calcium ions then trigger a biochemical cascade which results in vesicles fusing with the presynaptic membrane and releasing their contents to the synaptic cleft within 180 µs of calcium entry. Triggered by the binding of the calcium ions, the synaptic vesicle proteins begin to move apart, resulting in the creation of a fusion pore. The presence of the pore allows for the release of neurotransmitter into the synaptic"
"Chemical synapse Chemical synapses are biological junctions through which neurons' signals can be exchanged to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous system. They are crucial to the biological computations that underlie perception and thought. They allow the nervous system to connect to and control other systems of the body. At a chemical synapse, one neuron releases neurotransmitter molecules into a small space (the synaptic cleft) that is adjacent to another neuron. The neurotransmitters are kept within small sacs called synaptic vesicles, and"
"molecules (SAMs) projecting from both the pre- and post-synaptic neuron and sticking together where they overlap; SAMs may also assist in the generation and functioning of synapses. There are two fundamentally different types of synapses: Synaptic communication is distinct from an ephaptic coupling, in which communication between neurons occurs via indirect electric fields. An autapse is a chemical or electrical synapse that forms when the axon of one neuron synapses onto dendrites of the same neuron. Synapses can be classified by the type of cellular structures serving as the pre- and post-synaptic components. The vast majority of synapses in the"
"Synaptogenesis Synaptogenesis is the formation of synapses between neurons in the nervous system. Although it occurs throughout a healthy person's lifespan, an explosion of synapse formation occurs during early brain development, known as exuberant synaptogenesis. Synaptogenesis is particularly important during an individual's critical period, during which there is a certain degree of synaptic pruning due to competition for neural growth factors by neurons and synapses. Processes that are not used, or inhibited during their critical period will fail to develop normally later on in life. The neuromuscular junction (NMJ) is the most well-characterized synapse in that it provides a simple"
"cells do not actually touch each other. Instead, when the end of a nerve is activated it releases ions or chemicals known as neurotransmitters. Subsequently, these move across the gap, or synapse, between the neuron and the adjacent cell in the network, activating its receptors and perpetuating the signal. Jack applies theoretical and experimental approaches to research this process of synaptic transmission. This includes the use of neurophysiology methods to record bioelectrical activity and mathematical models to analyse the central and peripheral nervous systems. His work on neurotransmission is offering insight into disorders of the nervous system, such as Alzheimer’s"
"synaptic transmission, whereby a nerve impulse that has reached the end of one neuron is conveyed to an adjacent neuron via the release of neurotransmitters. This transmission is made possible by the action of synaptic vesicles loaded with the neurotransmitters to be released. These vesicles fuse with the cell membrane at the pre-synaptic terminal and release its contents to the exterior of the cell. The contents then diffuse across the synapse to the post-synaptic terminal. Lipid bilayers are also involved in signal transduction through their role as the home of integral membrane proteins. This is an extremely broad and important"
"in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials. Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell. Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication,"
"Gap junction A gap junction may also be called a nexus or macula communicans. (Although most nerve tissues don't have gap junctions, when found in neurons or nerves it may also be called an electrical synapse, like nerve cells in dental pulp.) While an ephapse has some similarities to a gap junction, by modern definition the two are different. Gap junctions are a specialized intercellular connection between a multitude of animal cell-types. They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells. One gap junction"
"the nerves in the cranium allowed him to differentiate between blood vessels and nerves i.e. , ""“string (plant fiber), nerve”"". Nerve A nerve is an enclosed, cable-like bundle of nerve fibres called axons, in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses called action potentials that are transmitted along each of the axons to peripheral organs or, in the case of sensory nerves, from the periphery back to the central nervous system. Each axon within the nerve is an extension of an individual neuron, along with other supportive cells such as Schwann cells"
"the ways in which one neuron communicates with another through synaptic connections and the process called synaptic transmission"". Neurons have a specialized structure for their function, they ""are different from most other cells in the body in that they are polarized and have distinct morphological regions, each with specific functions"". The two important regions of a neuron are the dendrite and the axon. ""Dendrites are the region where one neuron receives connections from other neurons. The cell body or soma contains the nucleus and the other organelles necessary for cellular function. The axon is a key component of nerve cells"
"Neuromuscular junction A neuromuscular junction (or myoneural junction) is a chemical synapse formed by the contact between a motor neuron and a muscle fiber. It is at the neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy. Synaptic transmission at the neuromuscular junction begins when an action potential reaches the presynaptic terminal of a motor neuron, which activates voltage-dependent calcium channels to allow calcium ions to enter the neuron. Calcium ions bind to sensor proteins (synaptotagmin) on"
"than that of the originating neuron. Electrical synapses are often found in neural systems that require the fastest possible response, such as defensive reflexes. An important characteristic of electrical synapses is that they are mostly bidirectional (allow impulse transmission in either direction). Each gap junction (aka nexus junction) contains numerous gap junction channels that cross the membranes of both cells. With a lumen diameter of about 1.2 to 2.0 nm, the pore of a gap junction channel is wide enough to allow ions and even medium-size molecules like signaling molecules to flow from one cell to the next, thereby connecting"
"Nerve A nerve is an enclosed, cable-like bundle of nerve fibres called axons, in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses called action potentials that are transmitted along each of the axons to peripheral organs or, in the case of sensory nerves, from the periphery back to the central nervous system. Each axon within the nerve is an extension of an individual neuron, along with other supportive cells such as Schwann cells that coat the axons in myelin. Within a nerve, each axon is surrounded by a layer of connective tissue called"
"to the gills, ""aplysia"" no longer withdraws them. It has gone through habituation, a process by which the response to a stimulus becomes weaker with more exposure. This occurs because of changes in the nervous system. Neurons communicate with one another at synapses, which consist of the tip of the communicating cell (the presynpatic membrane), the tip of the receiving cell (the postsynaptic membrane), and the space in between the two (the synaptic cleft). When the presynaptic membrane is stimulated by the influx of calcium ions, it releases a chemical called a neurotransmitter, which travels over the synaptic cleft in"
"and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It"
"travel long distances in the body, and, to accomplish this, many axons relay their message to a second cell through synaptic transmission. The ends of the axons link across a space, the synapse, to the dendrites of the second cell. The first cell (the presynaptic cell) sends a neurotransmitter across the synaptic cleft where it activates the second cell (the postsynaptic cell). The message is then carried to the final destination. Presynaptic nerves' axons terminate in either the paravertebral ganglia or prevertebral ganglia. There are four different paths an axon can take before reaching its terminal. In all cases, the"
"cells, known as a gap junction. At gap junctions, cells approach within about 3.5 nm of each other, rather than the 20 to 40 nm distance that separates cells at chemical synapses. As opposed to chemical synapses, the postsynaptic potential in electrical synapses is not caused by the opening of ion channels by chemical transmitters, but rather by direct electrical coupling between both neurons. Electrical synapses are faster than chemical synapses. Electrical synapses are found throughout the nervous system, including in the retina, the reticular nucleus of the thalamus, the neocortex, and in the hippocampus. While chemical synapses are found"