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Ephaptic Coupling
Ephaptic coupling is a form of communication within the nervous system and is distinct from direct communication systems like electrical synapses and chemical synapses. It may refer to the coupling of adjacent (touching) nerve fibers caused by the exchange of ions between the cells, or it may refer to coupling of nerve fibers as a result of local electric fields.Aur D., Jog, MS. (2010) ''Neuroelectrodynamics: Understanding the brain language'', IOS Press, In either case ephaptic coupling can influence the synchronization and timing of action potential firing in neurons. Myelination is thought to inhibit ephaptic interactions. History and etymology The idea that the electrical activity generated by nervous tissue may influence the activity of surrounding nervous tissue is one that dates back to the late 19th century. Early experiments, like those by du Bois-Reymond, demonstrated that the firing of a primary nerve may induce the firing of an adjacent secondary nerve (termed "seco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nervous System
In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called motor nerves or '' efferent'' nerves, while those nerves that transmit information from the body to the CNS are called sensory nerves or '' afferent''. Spinal nerves are mixed nerves that serve both fu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliary Ganglion
The ciliary ganglion is a bundle of nerve parasympathetic ganglion located just behind the eye in the posterior orbit. It is 1–2 mm in diameter and in humans contains approximately 2,500 neurons. The ganglion contains postganglionic parasympathetic neurons. These neurons supply the pupillary sphincter muscle, which constricts the pupil, and the ciliary muscle which contracts to make the lens more convex. Both of these muscles are involuntary since they are controlled by the parasympathetic division of the autonomic nervous system. The ciliary ganglion is one of four parasympathetic ganglia of the head. The others are the submandibular ganglion, pterygopalatine ganglion, and otic ganglion. Structure The ciliary ganglion contains postganglionic parasympathetic neurons that supply the ciliary muscle and the pupillary sphincter muscle. Because of the much larger size of the ciliary muscle, 95% of the neurons in the ciliary ganglion innervate it compared to the pupillary sphincter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurophysiology
Neurophysiology is a branch of physiology and neuroscience that studies nervous system function rather than nervous system architecture. This area aids in the diagnosis and monitoring of neurological diseases. Historically, it has been dominated by electrophysiology—the electrical recording of neural activity ranging from the molar (the electroencephalogram, EEG) to the cellular (intracellular recording of the properties of single neurons), such as patch clamp, voltage clamp, extracellular single-unit recording and recording of local field potentials. However, since the neurone is an electrochemical machine, it is difficult to isolate electrical events from the metabolic and molecular processes that cause them. Thus, neurophysiologists currently utilise tools from chemistry (calcium imaging), physics (functional magnetic resonance imaging, Functional magnetic resonance imaging, fMRI), and molecular biology (site directed mutations) to examine brain activity. The word originates f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Local Field Potential
Local field potentials (LFP) are transient electrical signals generated in nervous and other tissues by the summed and synchronous electrical activity of the individual cells (e.g. neurons) in that tissue. LFP are "extracellular" signals, meaning that they are generated by transient imbalances in ion concentrations in the spaces outside the cells, that result from cellular electrical activity. LFP are 'local' because they are recorded by an electrode placed nearby the generating cells. As a result of the Inverse-square law, such electrodes can only 'see' potentials in spatially limited radius. They are 'potentials' because they are generated by the voltage that results from charge separation in the extracellular space. They are 'field' because those extracellular charge separations essentially create a local electric field. LFP are typically recorded with a high-impedance microelectrode placed in the midst of the population of cells generating it. They can be recorded, for exam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NeuroElectroDynamics
Neural coding (or Neural representation) is a neuroscience field concerned with characterising the hypothetical relationship between the stimulus and the individual or ensemble neuronal responses and the relationship among the electrical activity of the neurons in the ensemble. Based on the theory that sensory and other information is represented in the brain by networks of neurons, it is thought that neurons can encode both digital and analog information. Overview Neurons are remarkable among the cells of the body in their ability to propagate signals rapidly over large distances. They do this by generating characteristic electrical pulses called action potentials: voltage spikes that can travel down axons. Sensory neurons change their activities by firing sequences of action potentials in various temporal patterns, with the presence of external sensory stimuli, such as light, sound, taste, smell and touch. It is known that information about the stimulus is encoded in this patt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electroencephalography
Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex and allocortex. It is typically non-invasive, with the EEG electrodes placed along the scalp (commonly called "scalp EEG") using the International 10-20 system, or variations of it. Electrocorticography, involving surgical placement of electrodes, is sometimes called " intracranial EEG". Clinical interpretation of EEG recordings is most often performed by visual inspection of the tracing or quantitative EEG analysis. Voltage fluctuations measured by the EEG bioamplifier and electrodes allow the evaluation of normal brain activity. As the electrical activity monitored by EEG originates in neurons in the underlying brain tissue, the recordings made by the electrodes on the surface of the scalp vary in accordance with their orientation and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saltatory Conduction
In neuroscience, saltatory conduction () is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials. The uninsulated nodes of Ranvier are the only places along the axon where ions are exchanged across the axon membrane, regenerating the action potential between regions of the axon that are insulated by myelin, unlike electrical conduction in a simple circuit. Mechanism Myelinated axons only allow action potentials to occur at the unmyelinated nodes of Ranvier that occur between the myelinated internodes. It is by this restriction that saltatory conduction propagates an action potential along the axon of a neuron at rates significantly higher than would be possible in unmyelinated axons (150 m/s compared to 0.5 to 10 m/s). As sodium rushes into the node it creates an electrical force which pushes on the ions already inside the axon. This rapid conduction of electrical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teleostei
Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest class (biology), infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all neontology, extant species of fish. Teleosts are arranged into about 40 order (biology), orders and 448 family (biology), families. Over 26,000 species have been described. Teleosts range from giant oarfish measuring or more, and ocean sunfish weighing over , to the minute male anglerfish ''Photocorynus spiniceps'', just long. Including not only torpedo-shaped fish built for speed, teleosts can be flattened vertically or horizontally, be elongated cylinders or take specialised shapes as in anglerfish and seahorses. The difference between teleosts and other bony fish lies mainly in their jaw bones; teleosts have a movable premaxilla and corresponding modifications in the jaw musculature which make it possible for them to cranial kinesi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basket Cell
Basket cells are inhibitory GABAergic interneurons of the brain, found throughout different regions of the cortex and cerebellum. Anatomy and physiology Basket cells are multipolar GABAergic interneurons that function to make inhibitory synapses and control the overall potentials of target cells. In general, dendrites of basket cells are free branching, contain smooth spines, and extend from 3 to 9 mm. Axons are highly branched, ranging in total from 20 to 50mm in total length. The branched axonal arborizations give rise to the name as they appear as baskets surrounding the soma of the target cell. Basket cells form axo-somatic synapses, meaning their synapses target somas of other cells. By controlling the somas of other neurons, basket cells can directly control the action potential discharge rate of target cells. Basket cells can be found throughout the brain, in among other the cortex, hippocampus, amygdala, basal ganglia, and the cerebellum. Cortex In the cortex, basket cell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Purkinje Cell
Purkinje cells, or Purkinje neurons, are a class of GABAergic inhibitory neurons located in the cerebellum. They are named after their discoverer, Czech people, Czech anatomist Jan Evangelista Purkyně, who characterized the cells in 1839. Structure These Cell (biology), cells are some of the largest neurons in the human brain (Betz cells being the largest), with an intricately elaborate dendrite, dendritic arbor, characterized by a large number of dendritic spines. Purkinje cells are found within the Cerebellum#Microanatomy, Purkinje layer in the cerebellum. Purkinje cells are aligned like dominos stacked one in front of the other. Their large dendritic arbors form nearly two-dimensional layers through which parallel fibers from the deeper-layers pass. These parallel fibers make relatively weaker excitatory synapse, excitatory (glutamatergic) synapses to spines in the Purkinje cell dendrite, whereas climbing fibers originating from the inferior olivary nucleus in the medull ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cable Theory
Classical cable theory uses mathematical models to calculate the electric current (and accompanying voltage) along passive neurites, particularly the dendrites that receive synaptic inputs at different sites and times. Estimates are made by modeling dendrites and axons as cylinders composed of segments with capacitances c_m and resistances r_m combined in parallel (see Fig. 1). The capacitance of a neuronal fiber comes about because electrostatic forces are acting through the very thin lipid bilayer (see Figure 2). The resistance in series along the fiber r_l is due to the axoplasm's significant resistance to movement of electric charge. History Cable theory in computational neuroscience has roots leading back to the 1850s, when Professor William Thomson (later known as Lord Kelvin) began developing mathematical models of signal decay in submarine (underwater) telegraphic cables. The models resembled the partial differential equations used by Fourier to describe heat cond ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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