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Neuronal Self-avoidance
Neuronal self-avoidance, or isoneural avoidance, is an important property of neurons which consists in the tendency of branches (dendrites and axons) arising from a single soma (also called isoneuronal or sister branches) to turn away from one another. The arrangements of branches within neuronal arbors are established during development and result in minimal crossing or overlapKramer AP, Stent GS. 1985. Developmental arborization of sensory neurons in the leech Haementeria ghilianii. II. Experimentally induced variations in the branching pattern. J. Neurosci., 5:768–75 as they spread over a territory, resulting in the typical fasciculated morphology of neurons (Fig 1). In opposition, branches from different neurons can overlap freely with one another. This propriety demands that neurons are able to discriminate "self", which they avoid, from "non-self" branches, with which they coexist.Kramer AP, Kuwada JY. 1983. Formation of the receptive fields of leech mechanosensory neurons ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenomena Selfrecogn
A phenomenon ( : phenomena) is an observable event. The term came into its modern philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be directly observed. Kant was heavily influenced by Gottfried Wilhelm Leibniz in this part of his philosophy, in which phenomenon and noumenon serve as interrelated technical terms. Far predating this, the ancient Greek Pyrrhonist philosopher Sextus Empiricus also used ''phenomenon'' and ''noumenon'' as interrelated technical terms. Common usage In popular usage, a ''phenomenon'' often refers to an extraordinary event. The term is most commonly used to refer to occurrences that at first defy explanation or baffle the observer. According to the ''Dictionary of Visual Discourse'':In ordinary language 'phenomenon/phenomena' refer to any occurrence worthy of note and investigation, typically an untoward or unusual event, person or fact that is of special significance or otherwise notable. Philosophy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Purkinje Cells
Purkinje cells, or Purkinje neurons, are a class of GABAergic inhibitory neurons located in the cerebellum. They are named after their discoverer, Czech anatomist Jan Evangelista Purkyně, who characterized the cells in 1839. Structure These cells are some of the largest neurons in the human brain (Betz cells being the largest), with an intricately elaborate dendritic arbor, characterized by a large number of dendritic spines. Purkinje cells are found within the 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 (glutamatergic) synapses to spines in the Purkinje cell dendrite, whereas climbing fibers originating from the inferior olivary nucleus in the medulla provide very powerful excitatory input to the proximal dendrites and cell soma. P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trigeminal Ganglion
A trigeminal ganglion (or Gasserian ganglion, or semilunar ganglion, or Gasser's ganglion) is the sensory ganglion at the base of each of the two trigeminal nerves (CN V), occupying a cavity (Meckel's cave) in the dura mater, covering the trigeminal impression near the apex of the petrous part of the temporal bone. Structure It is somewhat crescent-shaped, with its convexity directed forward: Medially, it is in relation with the internal carotid artery and the posterior part of the cavernous sinus. The motor root runs in front of and medial to the sensory root, and passes beneath the ganglion; it leaves the skull through the foramen ovale, and, immediately below this foramen, joins the mandibular nerve. The greater superficial petrosal nerve lies also underneath the ganglion. The ganglion receives, on its medial side, filaments from the carotid plexus of the sympathetic. It gives off minute branches to the tentorium cerebelli, and to the dura mater in the middle fossa of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trigeminal Nerve
In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the most complex of the cranial nerves. Its name ("trigeminal", ) derives from each of the two nerves (one on each side of the pons) having three major branches: the ophthalmic nerve (V), the maxillary nerve (V), and the mandibular nerve (V). The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve supplies motor as well as sensory (or "cutaneous") functions. Adding to the complexity of this nerve is that autonomic nerve fibers as well as special sensory fibers (taste) are contained within it. The motor division of the trigeminal nerve derives from the basal plate of the embryonic pons, and the sensory division originates in the cranial neural crest. Sensory information from the face and body is proc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenopus Laevis
The African clawed frog (''Xenopus laevis'', also known as the xenopus, African clawed toad, African claw-toed frog or the ''platanna'') is a species of African aquatic frog of the family Pipidae. Its name is derived from the three short claws on each hind foot, which it uses to tear apart its food. The word ''Xenopus'' means 'strange foot' and ''laevis'' means 'smooth'. The species is found throughout much of Sub-Saharan Africa (Nigeria and Sudan to South Africa),Weldon; du Preez; Hyatt; Muller; and Speare (2004). Origin of the Amphibian Chytrid Fungus.' Emerging Infectious Diseases 10(12). and in isolated, introduced populations in North America, South America, Europe, and Asia. All species of the family Pipidae are tongueless, toothless and completely aquatic. They use their hands to shove food in their mouths and down their throats and a hyobranchial pump to draw or suck things in their mouth. Pipidae have powerful legs for swimming and lunging after food. They also use the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synapse
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to the transmission of nervous impulses from one neuron to another. Neurons are specialized to pass signals to individual target cells, and synapses are the means by which they do so. At 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 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. Syna ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dirichlet Distribution
In probability and statistics, the Dirichlet distribution (after Peter Gustav Lejeune Dirichlet), often denoted \operatorname(\boldsymbol\alpha), is a family of continuous multivariate probability distributions parameterized by a vector \boldsymbol\alpha of positive reals. It is a multivariate generalization of the beta distribution, (Chapter 49: Dirichlet and Inverted Dirichlet Distributions) hence its alternative name of multivariate beta distribution (MBD). Dirichlet distributions are commonly used as prior distributions in Bayesian statistics, and in fact, the Dirichlet distribution is the conjugate prior of the categorical distribution and multinomial distribution. The infinite-dimensional generalization of the Dirichlet distribution is the ''Dirichlet process''. Definitions Probability density function The Dirichlet distribution of order ''K'' ≥ 2 with parameters ''α''1, ..., ''α''''K'' > 0 has a probability density function with respect to Lebesgue m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception. The retina serves a function which is in many ways analogous to that of the film or image sensor in a camera. The neural retina consists of several layers of neurons interconnected by synapses and is supported by an outer layer of pigmented epithelial cells. The primary light-sensing cells in the retina are the photoreceptor cells, which are of two types: rods and cones. Rods function mainly in dim light and provide monochromatic vision. Cones function in well-lit conditions and are responsible for the perception of colour through the use of a range of opsins, as well as high-acuity vision used for task ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neuronal Tiling
Neuronal tiling is a phenomenon in which multiple arbors of neurons innervate the same surface or tissue in a nonredundant and tiled pattern that maximizes coverage of the surface while minimizing overlap between neighboring arbors.Grueber, W. B. & Sagasti, A. Self-avoidance and tiling: Mechanisms of dendrite and axon spacing. Cold Spring Harb. Perspect. Biol. 2, a001750 (2010) Hence, dendrites of the same neuron spread out by avoiding one another ( self-avoidance). Moreover, dendrites of certain types of neurons such as class III and class IV dendritic arborization neurons avoid dendrites of neighboring neurons of the same type (tiling), whereas dendrites of different neuronal types can cover the same territory (coexistence).1. Jan, Y.-N. & Jan, L. Y. Branching out: mechanisms of dendritic arborization. Nat. Rev. Neurosci. 11, 316–28 (2010). One good example of this organization is the cell bodies The soma (pl. ''somata'' or ''somas''), perikaryon (pl. ''perikarya''), neurocyton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinal Ganglion Cell
A retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the ganglion cell layer) of the retina of the human eye, eye. It receives visual information from photoreceptor cell, photoreceptors via two intermediate neuron types: Bipolar cell of the retina, bipolar cells and retina amacrine cells. Retina amacrine cells, particularly narrow field cells, are important for creating functional subunits within the ganglion cell layer and making it so that ganglion cells can observe a small dot moving a small distance. Retinal ganglion cells collectively transmit image-forming and non-image forming visual information from the retina in the form of action potential to several regions in the thalamus, hypothalamus, and mesencephalon, or midbrain. Retinal ganglion cells vary significantly in terms of their size, connections, and responses to visual stimulation but they all share the defining property of having a long axon that extends into the brain. These axons form th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timeline History (2)
The following is a list of timeline articles: Prehistory *For events dating from the formation of the universe see: Timeline of the early universe and Timeline of the universe *For events dating from the formation of the planet to the rise of modern humans see: Timeline of natural history, Timeline of the evolutionary history of life, Timeline of life and Timeline of human development *For events dating from the first appearance of ''Homo sapiens'' to before the invention of writing see: Timeline of prehistory History These timelines of world history detail recorded events since the creation of writing roughly 5000 years ago to the present day. *For events from see: Timeline of ancient history *For events from , see: Timeline of the Middle Ages *For events from , see: Timelines of modern history Future *For future timelines, see: Timelines of the future See also * ChronoZoom * History by period * List of years * List of decades, centuries, and millennia This is a list ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protocadherin
Protocadherins (Pcdhs) are the largest mammalian subgroup of the cadherin superfamily of homophilic cell-adhesion proteins. They were discovered by Shintaro Suzuki's group, when they used PCR to find new members of the cadherin family. The PCR fragments that corresponded to protocadherins were found in vertebrate and invertebrate species. This prevalence in a wide range of species suggested that the fragments were part of an ancient cadherin and were thus termed "Protocadherins" as the "first cadherins". Of the approximately 70 Pcdh genes identified in mammalian genomes, over 50 are located in tightly linked gene clusters on the same chromosome. Until recently, it was assumed that this kind of organization can only be found in vertebrates, but '' Octopus bimaculoides'' has 168 genes of which nearly three-quarters are found in tandem clusters with the two largest clusters compromising 31 and 17 genes, respectively. Classification In mammals, two types of Pcdh genes have been def ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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