query: where are the cell bodies of efferent motor neurons found

pos: Motor neuron Motor neuron A motor neuron (or motoneuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. There are two types of motor neuron – upper motor neurons and lower motor neurons. Axons from upper motor neurons synapse onto interneurons in the spinal cord and occasionally directly onto lower motor neurons. The axons from the lower motor neurons are efferent nerve fibers that carry signals from the

pos: Somatic nervous system the efferent somatic nervous system involves a sequence that begins in the upper cell bodies of motor neurons (upper motor neurons) within the precentral gyrus (which approximates the primary motor cortex). Stimuli from the precentral gyrus are transmitted from upper motor neurons and down the corticospinal tract, via axons to control skeletal (voluntary) muscles. These stimuli are conveyed from upper motor neurons through the ventral horn of the spinal cord, and across synapses to be received by the sensory receptors of alpha motor neurons (large lower motor neurons) of the brainstem and spinal cord. Upper motor neurons release a neurotransmitter,

pos: Upper motor neuron Upper motor neuron Upper motor neurons (UMNs) are the main source of voluntary movement. They are found in the brain and carry motor information down the spinal cord to activate the lower motor neurons, which in turn directly signal muscles to contract. They are a type of giant pyramidal cell called "Betz cells" and are found just below the surface of the cerebral cortex within layer V of the primary motor cortex. The cell bodies of "Betz cell" neurons are the largest in the brain, approaching nearly 0.1mm in diameter. The primary motor cortex, or precentral gyrus, is one of

pos: Motor neuron Motor neuron A motor neuron (or motoneuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. There are two types of motor neuron – upper motor neurons and lower motor neurons. Axons from upper motor neurons synapse onto interneurons in the spinal cord and occasionally directly onto lower motor neurons. The axons from the lower motor neurons are efferent nerve fibers that carry signals from the

pos: Upper motor neuron contraction/relaxation of a muscle), and an extensor plantar response known as the Babinski sign. Upper motor neuron Upper motor neurons (UMNs) are the main source of voluntary movement. They are found in the brain and carry motor information down the spinal cord to activate the lower motor neurons, which in turn directly signal muscles to contract. They are a type of giant pyramidal cell called "Betz cells" and are found just below the surface of the cerebral cortex within layer V of the primary motor cortex. The cell bodies of "Betz cell" neurons are the largest in the brain, approaching

pos: Alpha motor neuron Alpha motor neuron Alpha (α) motor neurons (also called alpha motoneurons), are large, multipolar lower motor neurons of the brainstem and spinal cord. They innervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating their contraction. Alpha motor neurons are distinct from gamma motor neurons, which innervate intrafusal muscle fibers of muscle spindles. While their cell bodies are found in the central nervous system (CNS), α motor neurons are also considered part of the somatic nervous system—a branch of the peripheral nervous system (PNS)—because their axons extend into the periphery to innervate skeletal muscles. An alpha motor

pos: Spinal interneuron Spinal interneuron A spinal interneuron, found in the spinal cord, relays signals between (afferent) sensory neurons, and (efferent) motor neurons. Different classes of spinal interneurons are involved in the process of sensory-motor integration. Most interneurons are found in the grey column, a region of grey matter in the spinal cord. The grey column of the spinal cord appears to have groups of small neurons, often referred to as spinal interneurons, that are neither primary sensory cells nor motor neurons. The versatile properties of these spinal interneurons cover a wide range of activities. Their functions include the processing of sensory input,

pos: Spinal interneuron into the contralateral spinal cord. At that location, the interneuron excites the alpha motor neurons that innervate the extensor muscles of the opposite leg. This allows for balance and body posture to be maintained. Spinal interneuron A spinal interneuron, found in the spinal cord, relays signals between (afferent) sensory neurons, and (efferent) motor neurons. Different classes of spinal interneurons are involved in the process of sensory-motor integration. Most interneurons are found in the grey column, a region of grey matter in the spinal cord. The grey column of the spinal cord appears to have groups of small neurons, often referred

pos: Alpha motor neuron lower limbs: these α-MNs form large cell columns that contribute to the cervical and lumbar enlargements of the spinal cord. In addition to receiving neurotrophic factors from muscles, α-MNs also secrete a number of trophic factors to support the muscle fibers they innervate. Reduced levels of trophic factors contributes to the muscle atrophy that follows an α-MN lesion. Like other neurons, lower motor neurons have both afferent (incoming) and efferent (outgoing) connections. Alpha motor neurons receive input from a number of sources, including upper motor neurons, sensory neurons, and interneurons. The primary output of α-MNs is to extrafusal muscle fibers.

pos: Alpha motor neuron neuron and the muscle fibers it innervates is a motor unit. A motor neuron pool contains the cell bodies of all the alpha motor neurons involved in contracting a single muscle. Alpha motor neurons (α-MNs) innervating the head and neck are found in the brainstem; the remaining α-MNs innervate the rest of the body and are found in the spinal cord. There are more α-MNs in the spinal cord than in the brainstem, as the number of α-MNs is directly proportional to the amount of fine motor control in that muscle. For example, the muscles of a single finger have

pos: Gamma motor neuron beta motor neurons and gamma motor neurons. Because beta motor neurons innervate extrafusal as well as intrafusal muscle fibers, they are more specifically named skeletofusimotor neurons. Gamma motor neurons are the efferent (sending signals away from the central nervous system) part of the fusimotor system, whereas muscle spindles are the afferent part, as they send signals relaying information from muscles toward the spinal cord and brain. Gamma bias is gamma motor neurons' consistent level of activity. Smaller neurons require a smaller amount of excitatory input to reach its threshold compared to larger neurons. Therefore, gamma motor neurons (smaller in size

pos: Beta motor neuron Beta motor neuron Beta motor neurons (β motor neurons), also called beta motoneurons, are a kind of lower motor neuron, along with alpha motor neurons and gamma motor neurons. Beta motor neurons innervate intrafusal fibers of muscle spindles with collaterals to extrafusal fibers - a type of slow twitch fiber. Also, axons of alpha, beta, and gamma motor neurons become myelinated. Moreover, these efferent neurons originate from the anterior grey column of the spinal cord and travel to skeletal muscles. However, the larger diameter alpha motor fibers require higher conduction velocity than beta and gamma. There are two kinds of

pos: Gamma motor neuron Gamma motor neuron A gamma motor neuron (γ motor neuron), also called gamma motoneuron, is a type of lower motor neuron that takes part in the process of muscle contraction, and represents about 30% of (Aγ) fibers going to the muscle. Like alpha motor neurons, their cell bodies are located in the anterior grey column of the spinal cord. They receive input from the reticular formation of the pons in the brainstem. Their axons are smaller than those of the alpha motor neurons, with a diameter of only 5 μm. Unlike the alpha motor neurons, gamma motor neurons do not

pos: Afferent nerve fiber Afferent nerve fiber Afferent nerve fibers refer to axonal projections that arrive at a particular region; as opposed to efferent projections that exit the region. These terms have a slightly different meaning in the context of the peripheral nervous system (PNS) and central nervous system (CNS). In the PNS, afferent and efferent projections are always from the perspective of the spinal cord (see figures). PNS afferents are the axons of sensory neurons carrying sensory information from all over the body, "into" the spine. PNS efferents are the axons of spinal cord motor neurons that carry motor-movement signals "out of" the

pos: Sensory loss pain, are most commonly a result of a more general physical impairment associated with paralysis. Damage to the spinal cord or other major nerve fiber may lead to a termination of both afferent and efferent signals to varying areas of the body, causing both a loss of touch and a loss of motor coordination. Other types of somatosensory loss include hereditary sensory and autonomic neuropathy, which consists of ineffective afferent neurons with fully functioning efferent neurons; essentially, motor movement without somatosensation. Sensory loss can occur due to a minor nick or lesion on the spinal cord which creates a problem

pos: Spinal interneuron least 17 different subclasses of interneurons with ipsilateral axon projections were found. In addition, 18 types of commissural interneurons have been identified on the basis of morphology and location. In particular, the cell bodies of the spinal interneurons are found in the grey matter of the spinal cord, which also contains the motor neurons. In 1952, the grey matter of the cat's spinal cord was investigated, and it was shown to have ten distinct zones referred to as Rexed laminae. Eventually, the lamination pattern was also observed in several species including humans. Rexed laminae VII and VIII are locations where

pos: Neuromere can be anatomically divided into 31 spinal segments based on the origins of the spinal nerves. Each segment of the spinal cord is associated with a pair of ganglia, called dorsal root ganglia, which are situated just outside the spinal cord. These ganglia contain cell bodies of sensory neurons. Axons of these sensory neurons travel into the spinal cord via the dorsal roots. Ventral roots consist of axons from motor neurons, which bring information to the periphery from cell bodies within the CNS. Dorsal roots and ventral roots come together and exit the intervertebral foramina as they become spinal nerves.

pos: Vestibulospinal tract the spinal cord and terminate at the interneurons of laminae VII and VIII. Additionally, some neurons terminate directly on the dendrites of alpha motor neurons in the same laminae. The medial vestibulospinal tract is a group of descending extrapyramidal motor neurons, or efferent fibers found in the anterior funiculus, a bundle of nerve roots in the spinal cord. The medial vestibulospinal tract originates in the medial vestibular nucleus or Schwalbe's nucleus. The Schwalbe's nucleus extends from the rostral end of the inferior olivary nucleus of the medulla oblongata to the caudal portion of the pons. Medial vestibulospinal fibers join with

pos: Spinal cord the spinal cord via descending spinal cord tracts. Descending tracts involve two neurons: the upper motor neuron (UMN) and lower motor neuron (LMN). A nerve signal travels down the upper motor neuron until it synapses with the lower motor neuron in the spinal cord. Then, the lower motor neuron conducts the nerve signal to the spinal root where efferent nerve fibers carry the motor signal toward the target muscle. The descending tracts are composed of white matter. There are several descending tracts serving different functions. The corticospinal tracts (lateral and anterior) are responsible for coordinated limb movements. A congenital disorder

pos: Anterior grey column Anterior grey column The anterior grey column (also called the anterior cornu, anterior horn of spinal cord or ventral horn) is the front column of grey matter in the spinal cord. It is one of the three grey columns. The anterior grey column contains motor neurons that affect the skeletal muscles while the posterior grey column receives information regarding touch and sensation. The anterior grey column is the column where the cell bodies of alpha motor neurons are located. The anterior grey column, directed forward, is broad and of a rounded or quadrangular shape. Its posterior part is termed the

pos: Efferent nerve fiber are involved in muscle control, both skeletal and smooth muscle. The cell body of the motor neuron is connected to a single, long axon and several shorter dendrites projecting out of the cell body itself. This axon then forms a neuromuscular junction with the effectors. The cell body of the motor neuron is satellite-shaped. The motor neuron is present in the grey matter of the spinal cord and medulla oblongata, and forms an electrochemical pathway to the effector organ or muscle. Besides motor nerves, there are efferent sensory nerves that often serve to adjust the sensitivity of the signal relayed

pos: Pyramidal tracts form the lateral corticospinal tract; 10% do not cross over and join the tract, and 10% of fibres travel in the anterior corticospinal tract. The nerve axons traveling down the tract are the efferent nerve fibers of the upper motor neurons. These axons travel down the tracts in the white matter of the spinal cord until they reach the vertebral level of the muscle that they will innervate. At this point, the axons synapse with lower motor neurons. The majority of axons do not directly synapse with lower motor neurons, but instead synapse with an interneuron that then synapses with

pos: Neuromere The gray matter, in the center of the cord, is shaped like a butterfly and consists of cell bodies of interneurons and motor neurons. It also consists of neuroglia cells and unmyelinated axons. Projections of the gray matter (the “wings”) are called horns. Together, the gray horns and the gray commissure form the “gray H.” The white matter is located outside of the gray matter and consists almost totally of myelinated motor and sensory axons. “Columns” of white matter carry information either up or down the spinal cord. Within the CNS, nerve cell bodies are generally organized into functional clusters,

pos: Topographic map (neuroanatomy) cortical homunculus. This illustration is a fairly accurate representation of how much cortical area represents each body part or region. It also maps what part of the cortex represents each region of the body. Unlike the topographic maps of the senses, the neurons of the motor cortex are efferent neurons that exit the brain instead of bringing information to the brain through afferent connections. The motor system is responsible for initiating voluntary or planned movements (reflexes are mediated at the spinal cord level, so movements that associated with a reflex are not initiated by the motor cortex). The activation from

pos: Grey column spinal cord, is part of the sympathetic nervous system and receives input from brain stem, organs, and hypothalamus. The lateral column is only present in the thoracic region and upper lumbar segments. The lateral grey column contains neurons supplying nerves to the muscles of the limbs, preganglionic cell bodies of the autonomic nervous system and sensory relay neurons. Neurons in the anterior column have been shown to be affected by amyotrophic lateral sclerosis (ALS). The number of large alpha motor neurons and medium gamma motor neurons was greatly reduced and the number of small neurons was either slightly or greatly

pos: F wave nerve so that the impulse travels both distally (towards the muscle fiber) and proximally (back to the motor neurons of the spinal cord). (These directions are also known as orthodromic and antidromic, respectively.) When the "orthodromic" stimulus reaches the muscle fiber, it elicits a strong M-response indicative of muscle contraction. When the "antidromic" stimulus reaches the motor neuron cell bodies, a small portion of the motor neurons backfire and orthodromic wave travels back down the nerve towards the muscle. This reflected stimulus evokes small proportion of the muscle fibers causing a small, second CMAP called the F wave. Because a

pos: Nuclear chain fiber one end to muscle and the other end to a tendon is known as a Golgi tendon organ. However, Golgi tendon organs differ from nuclear chain and nuclear bag fibers in that they are considered in series rather than in parallel to the muscle fibers. As intrafusal muscle fibers, nuclear chain fibers both send afferent (sensory) innervation and receive efferent (motor) innervation. The afferent innervation is via type Ia sensory fibers and type II sensory fibers. These project to the nucleus proprius in the dorsal horn of the spinal cord. Efferent innervation is via static γ motor neurons. Stimulation of

pos: Neural pathway their dendrites or cell bodies. The axon of a nerve cell is, in general, responsible for transmitting information over a relatively long distance. Therefore, most neural pathways are made up of axons. If the axons have myelin sheaths, then the pathway appears bright white because myelin is primarily lipid. If most or all of the axons lack myelin sheaths (i.e., are "unmyelinated"), then the pathway will appear a darker beige color, which is generally called "grey". Some neurons are responsible for conveying information over long distances. For example, motor neurons, which travel from the spinal cord to the muscle, can

pos: Betz cell Betz cell Betz cells (also known as pyramidal cells of Betz) are giant pyramidal cells (neurons) located within the fifth layer of the grey matter in the primary motor cortex. They are named after Ukrainian scientist Vladimir Betz, who described them in his work published in 1874. These neurons are the largest in the central nervous system, sometimes reaching 100 μm in diameter. Betz cells are upper motor neurons that send their axons down to the spinal cord via the corticospinal tract, where in humans they synapse directly with anterior horn cells, which in turn synapse directly with their target

pos: Renshaw cell during the declining phase of the initial motor neuron soma spike giving an indication of the source and sequence of stimulation of the Renshaw cell. Renshaw cell Renshaw cells are inhibitory interneurons found in the gray matter of the spinal cord, and are associated in two ways with an alpha motor neuron. In this way, the Renshaw cell action represents a negative feedback mechanism. A Renshaw cell may be supplied by more than one alpha motor neuron collateral and it may synapse on multiple motor neurons. Although during embryonic development the Renshaw cells lack synapses from the dorsal root, prenatal

pos: Gait (human) gait, such as Parkinson’s. The cerebellum plays a major role in motor coordination. Regulation of gait by the cerebellum is referred to as “error/correction,” because the cerebellum responds to abnormalities in posture in order to coordinate proper movement. The cerebellum sends signals to the cerebral cortex and the brain stem in response to sensory signals received from the spinal cord. Efferent signals from these regions go to the spinal cord where motor neurons are activated to regulate gait. There are multiple pathways within the spinal cord which play a role in regulating gait: The so-called natural gaits, in increasing order

pos: Renshaw cell Renshaw cell Renshaw cells are inhibitory interneurons found in the gray matter of the spinal cord, and are associated in two ways with an alpha motor neuron. In this way, the Renshaw cell action represents a negative feedback mechanism. A Renshaw cell may be supplied by more than one alpha motor neuron collateral and it may synapse on multiple motor neurons. Although during embryonic development the Renshaw cells lack synapses from the dorsal root, prenatal and postnatal stages show the development of dorsal root originating synapses, which are functional and stimulate action potentials. But these decrease during development while acetylcholine

pos: PLXNA4A nucleus. Fibers expressed Plexin A4 in the lateral septum, nucleus accumbens, several thalamic nuclei, substantia nigra pars reticulata, zona incerta, pontine reticular formation, as well as in several cranial nerve nuclei. Plexin A4 has been found in dorsal and, to a greater extent, ventral horns of the spinal cord. Both motor neurons and interneurons in the ventral horn express Plexin A4. Motor axons exiting via the ventral roots and the ascending and descending white matter tracts express Plexin A4. In dorsal root ganglia, Plexin A4 is expressed in the neuronal cell bodies as well as the central and peripheral processes

pos: Basal plate (neural tube) notochord. Differentiation of neurons in the basal plate is under the influence of the protein Sonic hedgehog released by ventralizing structures, such as the notochord and floor plate. Basal plate (neural tube) In the developing nervous system, the basal plate is the region of the neural tube ventral to the sulcus limitans. It extends from the rostral mesencephalon to the end of the spinal cord and contains primarily motor neurons, whereas neurons found in the alar plate are primarily associated with sensory functions. The cell types of the basal plate include lower motor neurons and four types of interneuron. Initially,

pos: Vestibulospinal tract upper motor neuron tract consisting of two sub-pathways: The lateral vestibulospinal tract is a group of descending extrapyramidal motor neurons, or efferent nerve fibers. This tract is found in the lateral funiculus, a bundle of nerve roots in the spinal cord. The lateral vestibulospinal tract originates in the lateral vestibular nucleus or Deiters’ nucleus in the pons. The Deiters' nucleus extends from pontomedullary junction to the level of abducens nerve nucleus in the pons. Lateral vestibulospinal fibers descend uncrossed, or ipsilateral, in the anterior portion of the lateral funiculus of the spinal cord. Fibers run down the total length of

pos: UNC (biology) reaching out for a presynaptic axon. Despite the appearance of attaching to an axon, cell signaling is still required for complete synaptic formation. An experiment was performed to determine the role of UNC-5 in axonal growth after spinal cord injury. The netrin is expressed by neurons in the corticospinal and rubrospinal projections, and by intrinsic neurons of the spinal cord both before and after the injury. When testing in vitro UNC-5 receptor bodies are taken from the spinal cord to neutralize netrin-1 in myelin. This increases the neurite outgrowth from UNC-5 expressing spinal motor neurons. UNC-129 is a ligand in

pos: Basal plate (neural tube) Basal plate (neural tube) In the developing nervous system, the basal plate is the region of the neural tube ventral to the sulcus limitans. It extends from the rostral mesencephalon to the end of the spinal cord and contains primarily motor neurons, whereas neurons found in the alar plate are primarily associated with sensory functions. The cell types of the basal plate include lower motor neurons and four types of interneuron. Initially, the left and right sides of the basal plate are continuous, but during neurulation they become separated by the floor plate, and this process is directed by the

pos: Calcitonin gene-related peptide CGRP may differ depending on the location of synthesis. CGRP is derived mainly from the cell bodies of motor neurons when synthesized in the ventral horn of the spinal cord and may contribute to the regeneration of nervous tissue after injury. Conversely, CGRP is derived from dorsal root ganglion when synthesized in the dorsal horn of the spinal cord and may be linked to the transmission of pain. In the trigeminal vascular system, the cell bodies on the trigeminal ganglion are the main source of CGRP. CGRP is thought to play a role in cardiovascular homeostasis and nociception. CGRP mediates

pos: Pyramidal cell to five rapid action potentials. IB pyramidal neurons show no adaptation. Pyramidal neurons are the primary neural cell type in the corticospinal tract. Normal motor control depends on the development of connections between the axons in the corticospinal tract and the spinal cord. Pyramidal cell axons follow cues such as growth factors to make specific connections. With proper connections, pyramidal cells take part in the circuitry responsible for vision guided motor function. Pyramidal neurons in the prefrontal cortex are implicated in cognitive ability. In mammals, the complexity of pyramidal cells increases from posterior to anterior brain regions. The degree of

pos: Pyramidal tracts Pyramidal tracts The pyramidal tracts include both the corticobulbar tract and the corticospinal tract. These are aggregations of efferent nerve fibers from the upper motor neurons that travel from the cerebral cortex and terminate either in the brainstem ("corticobulbar") or spinal cord ("corticospinal") and are involved in the control of motor functions of the body. The corticobulbar tract conducts impulses from the brain to the cranial nerves. These nerves control the muscles of the face and neck and are involved in facial expression, mastication, swallowing, and other functions. The corticospinal tract conducts impulses from the brain to the spinal cord.

pos: Motor neuron PNS, which synapses onto the muscle. All vertebrate motor neurons are cholinergic, that is, they release the neurotransmitter acetylcholine. Parasympathetic ganglionic neurons are also cholinergic, whereas most sympathetic ganglionic neurons are noradrenergic, that is, they release the neurotransmitter noradrenaline. (see Table) Motor neuron A motor neuron (or motoneuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. There are two types of motor neuron – upper

pos: Pyramidal tracts the cruz cerebri (pedunculotomy). In National Lampoon's European Vacation, the Griswold family was asked about the pyramidal tracts on the game show "Pig in a Poke". Pyramidal tracts The pyramidal tracts include both the corticobulbar tract and the corticospinal tract. These are aggregations of efferent nerve fibers from the upper motor neurons that travel from the cerebral cortex and terminate either in the brainstem ("corticobulbar") or spinal cord ("corticospinal") and are involved in the control of motor functions of the body. The corticobulbar tract conducts impulses from the brain to the cranial nerves. These nerves control the muscles of the

neg: Dorsal nucleus of vagus nerve Dorsal nucleus of vagus nerve The dorsal nucleus of the vagus nerve (or posterior motor nucleus of vagus) is a cranial nerve nucleus for the vagus nerve in the medulla that lies ventral to the floor of the fourth ventricle. It mostly serves parasympathetic vagal functions in the gastrointestinal tract, lungs, and other thoracic and abdominal vagal innervations. The cell bodies for the preganglionic parasympathetic vagal neurons that innervate the heart reside in the nucleus ambiguus. Additional cell bodies are found in the nucleus ambiguus, which give rise to the branchial efferent motor fibers of the vagus nerve (CN X)

neg: Neuroeffector junction Neuroeffector junction A neuroeffector junction is a site where a motor neuron releases a neurotransmitter to affect a target—non-neuronal—cell. This junction functions like a synapse. However, unlike most neurons, somatic efferent motor neurons innervate skeletal muscle, and are always excitatory. Visceral efferent neurons innervate smooth muscle, cardiac muscle, and glands, and have the ability to be either excitatory or inhibitory in function. Neuroeffector junctions are known as neuromuscular junctions when the target cell is a muscle fiber. Non-synaptic transmission is characteristic of autonomic neuroeffector junctions. The structure of the autonomic neuromuscular junction consists of several essential features including that: the

neg: Facial nerve head and neck ganglia. The facial and intermediate nerves can be collectively referred to as the nervus intermediofacialis. The path of the facial nerve can be divided into six segments. Distal to stylomastoid foramen, the following nerves branch off the facial nerve: The cell bodies for the facial nerve are grouped in anatomical areas called nuclei or ganglia. The cell bodies for the afferent nerves are found in the geniculate ganglion for taste sensation. The cell bodies for muscular efferent nerves are found in the facial motor nucleus whereas the cell bodies for the parasympathetic efferent nerves are found in

neg: Spinal cord is made of 31 segments from which branch one pair of sensory nerve roots and one pair of motor nerve roots. The nerve roots then merge into bilaterally symmetrical pairs of spinal nerves. The peripheral nervous system is made up of these spinal roots, nerves, and ganglia. The dorsal roots are afferent fascicles, receiving sensory information from the skin, muscles, and visceral organs to be relayed to the brain. The roots terminate in dorsal root ganglia, which are composed of the cell bodies of the corresponding neurons. Ventral roots consist of efferent fibers that arise from motor neurons whose cell

neg: Neuroeffector junction afferents and ICC-IM within the stomach wall (Fig. 5) and their absence in mutant animals that lack ICC-IM also supports a role for ICC-IM as possible integrators for in-series stretch-dependent changes in this organ. Neuroeffector junction A neuroeffector junction is a site where a motor neuron releases a neurotransmitter to affect a target—non-neuronal—cell. This junction functions like a synapse. However, unlike most neurons, somatic efferent motor neurons innervate skeletal muscle, and are always excitatory. Visceral efferent neurons innervate smooth muscle, cardiac muscle, and glands, and have the ability to be either excitatory or inhibitory in function. Neuroeffector junctions are known

neg: Motor neuron categories: Somatic motor neurons originate in the central nervous system, project their axons to skeletal muscles (such as the muscles of the limbs, abdominal, and intercostal muscles), which are involved in locomotion. The three types of these neurons are the "alpha efferent neurons", "beta efferent neurons", and "gamma efferent neurons". They are called efferent to indicate the flow of information from the central nervous system (CNS) to the periphery. In addition to voluntary skeletal muscle contraction, alpha motor neurons also contribute to muscle tone, the continuous force generated by noncontracting muscle to oppose stretching. When a muscle is stretched, sensory

neg: Autonomic nervous system neuron will begin at the “outflow” and will synapse at the postganglionic, or second, neuron's cell body. The postganglionic neuron will then synapse at the target organ. The sympathetic nervous system consists of cells with bodies in the lateral grey column from T1 to L2/3. These cell bodies are "GVE" (general visceral efferent) neurons and are the preganglionic neurons. There are several locations upon which preganglionic neurons can synapse for their postganglionic neurons: These ganglia provide the postganglionic neurons from which innervation of target organs follows. Examples of splanchnic (visceral) nerves are: These all contain afferent (sensory) nerves as well,

neg: Efferent nerve fiber by the afferent sensory nerve. There are three types of efferent fibers: general somatic efferent fibers (GSE), general visceral efferent fibers (GVE) and special visceral efferent fibers (SVE). Subtypes of general somatic efferent fibers include: alpha motor neurons (α) – these target extrafusal muscle fibers, and gamma motor neurons (γ) that target intrafusal muscle fibers. Beta motor neurons target both types of muscle fiber and there are two types known as "static" and "dynamic". Both afferent and efferent come from French, evolved from Latin (the basis of many terms in medicine and biology) for the terms, respectively, "ad ferens" (Latin

neg: Gamma motor neuron in gamma motor neurons, but very little in alpha motor neurons. On the other hand, neuronal DNA binding protein NeuN, are present in significantly greater quantities in alpha motor neurons. Osteopontin, a protein also expressed in bones, hence the "osteo-" prefix, is a marker for alpha motor neurons. This in turn can provide scientists a way of eliminating gamma motor neurons if alpha motor neurons are of interest. One study in particular made this conclusion based on the fact that osteopontin was present in larger cell bodies, indicating the alpha motor neurons as they have larger cell bodies than gamma

neg: Efferent nerve fiber conduction, which carries impulses by way of the afferent nerve fibers of sensory neurons. In the nervous system there is a "closed loop" system of sensation, decision, and reactions. This process is carried out through the activity of sensory neurons, interneurons, and motor neurons. In the CNS, afferent and efferent projections can be from the perspective of any given brain region. That is, each brain region has its own unique set of afferent and efferent projections. In the context of a given brain region, afferents are arriving fibers while efferents are exiting fibers. The efferent nerve fibers of motor neurons

neg: Bipolar neuron Bipolar neuron A bipolar neuron or bipolar cell, is a type of neuron which has two extensions (one axon and one dendrite). Bipolar cells are specialized sensory neurons for the transmission of special senses. As such, they are part of the sensory pathways for smell, sight, taste, hearing and vestibular functions. Common examples are the bipolar cell of the retina, the ganglia of the vestibulocochlear nerve, and the extensive use of bipolar cells to transmit efferent (motor) signals to control muscles. Oftentimes found in the retina, bipolar cells are crucial as they serve as both direct and indirect cell pathways.

neg: Facial motor nucleus a dorsal and ventral region, with neurons in the dorsal region innervating muscles of the upper face and neurons in the ventral region innervating muscles of the lower face. Because it innervates muscles derived from pharyngeal arches, the facial motor nucleus is considered part of the special visceral efferent (SVE) cell column, which also includes the trigeminal motor nucleus, nucleus ambiguus, and (arguably) the spinal accessory nucleus. Like all lower motor neurons, cells of the facial motor nucleus receive cortical input from the primary motor cortex in the frontal lobe of the brain. Upper motor neurons of the cortex send

neg: Renshaw cell "et al.", provided evidence that these interneurons, which they called “Renshaw Cells,” are stimulated by acetylcholine from motor neurons. Previous work by Renshaw and Lloyd had shown that this antidromic inhibition resembled direct inhibition from spinal nerves but resulted in relatively longer inhibition of 40-50 ms (compared to 15 ms). The antidromic stimulation of the nerve fiber also resulted in action potentials in the cell bodies of the motor neurons along with hyperpolarization of other groups of motor neurons. In the event where the initial stimulation of the motor neuron originated in a spinal tract the Renshaw cell spike occurred

neg: Circumventricular organs is composed exclusively of the glial cells and neuronal cell bodies. Conversely, the rostral and caudal areas are mostly made of nerve fibers while very few neurons and glial cells can be seen in this area. Functionally, however, the SFO may be viewed in two portions, the dorsolateral peripheral (pSFO) division and the ventromedial core segment. As an important mechanism of both energy and osmotic homeostasis, the SFO has many efferent projections. In fact, SFO neurons have been experimentally shown to broadcast efferent projections to regions involved in cardiovascular regulation including the lateral hypothalamus with fibers terminating in the supraoptic

neg: Beta motor neuron beta motor neuron (as gamma motor neuron) that include: Gamma motor neurons innervate only intrafusal fibers of muscle spindles, but extrafusal fibers (i.e. slow and fast fibers) are innervated by alpha motoneurons. Beta motor neuron Beta motor neurons (β motor neurons), also called beta motoneurons, are a kind of lower motor neuron, along with alpha motor neurons and gamma motor neurons. Beta motor neurons innervate intrafusal fibers of muscle spindles with collaterals to extrafusal fibers - a type of slow twitch fiber. Also, axons of alpha, beta, and gamma motor neurons become myelinated. Moreover, these efferent neurons originate from the

neg: Gamma motor neuron of spindle fibers are located only at both ends of spindle. Efferent stimulation of the spindle by gamma motor neurons contracts the myofibrils, tautening the central region of spindle -- which maintains its sensitivity to gamma motoneuron stimulation. Without gamma motor neurons, muscle spindles would be very loose as the muscle contracts more. This does not allow for muscle spindles to detect a precise amount of stretch since it is so limp. However, with alpha gamma co-activation where both alpha neurons and gamma neurons are present, muscle fibers with the muscle spindles are pulled parallel to the extrafusal contraction causing

neg: Renshaw cell motor axons begin to synapse and proliferate with Renshaw cells, ultimately being primarily stimulated by the motor neurons. The Renshaw cells are ultimately excited by multiple antidromic motor neuron axons, where the majority of axons originate from synergist motor neurons, and in turn the Renshaw cell synapses with multiple neurons, eliciting IPSP in alpha motor, 1a inhibitory interneurons and gamma motor neurons. The antidromic collateral circuit back to the triggering motor neuron is known as “recurrent inhibition”. This homonymous inhibition is not universal. Whereas most initial experiments have been done on cats, it has been found that in man that

neg: Type Ia sensory fiber means "a ring-shaped area or structure". In addition, the spindle also has a motor efferent innervation carried by the efferent nerve fibers of gamma motor neurons, which is used by the nervous system to modify the spindle's sensitivity. Ia afferents from the muscle spindle terminate on the proximal dendrites of motor neurons. Type Ia sensory fiber A type Ia sensory fiber, or a primary afferent fiber is a type of afferent nerve fiber. It is the sensory fiber of a stretch receptor found in muscles called the muscle spindle, which constantly monitors how fast a muscle stretch changes. (In other

neg: Grey column manner as the muscles they innervate. Alpha motor neurons innervate extrafusal muscle fibers that generate force at neuromuscular junctions at the start of muscle contraction. They have large cell bodies and receive proprioceptive input. They have been shown to reduce in population, but not in size with age. Damage to these cell bodies can lead to severe muscle weakness and loss of reflexes. Gamma motor neurons innervate intrafusal muscle fibers that control the sensitivity of muscle spindles to stretch. They have smaller cell bodies than alpha motor neurons and do not receive proprioceptive input. They have been shown to reduce

neg: Rhombomere into r5 near the pial surface. Neurons that form the facial nucleus are produced in r4, but move along the anteroposterior axis of the hindbrain into r6, after which they move dorsolaterally. The vestibuloacoustic neurons are also produced in r4. However, they have a unique migration pattern, where their cell bodies cross the midline to the contralateral side. From this one can conclude that multiple subclasses of motor neurons are produced in specific locations in the developing hindbrain. All of them are related by the expression of Tbx20. Motor neurons produced in the hindbrain have Tbx20 selectively expressed. In Tbx20

neg: Pyramidal cell Pyramidal cell Pyramidal cells, or pyramidal neurons, are a type of multipolar neuron found in areas of the brain including the cerebral cortex, the hippocampus, and the amygdala. Pyramidal neurons are the primary excitation units of the mammalian prefrontal cortex and the corticospinal tract. Pyramidal neurons are also one of two cell types where the characteristic sign, Negri bodies, are found in post-mortem rabies infection. Pyramidal neurons were first discovered and studied by Santiago Ramón y Cajal. Since then, studies on pyramidal neurons have focused on topics ranging from neuroplasticity to cognition. One of the main structural features of the

neg: Ganglion Ganglion A ganglion is a nerve cell cluster or a group of nerve cell bodies located in the autonomic nervous system and sensory system. Ganglia house the cell bodies of afferent nerves (input nerve fibers) and efferent nerves (output/motor nerve fibers), or axons. A pseudoganglion looks like a ganglion, but only has nerve fibers and has no nerve cell bodies. Ganglia are primarily made up of somata and dendritic structures which are bundled or connected. Ganglia often interconnect with other ganglia to form a complex system of ganglia known as a plexus. Ganglia provide relay points and intermediary connections between

neg: Basal electrical rhythm the esophagus and towards the rectum. The smooth muscle throughout most of the GI tract is divided into two layers: an outer longitudinal layer and an inner circular layer. Both layers of muscle are located within the muscularis externa. The stomach has a third layer: an innermost oblique layer. The physical contractions of the smooth muscle cells can be caused by action potentials in efferent motor neurons of the enteric nervous system, or by receptor mediated calcium influx. These efferent motor neurons of the enteric nervous system are cholinergic and adrenergic neurons. The inner circular layer is innervated by both

neg: UNC-5 expression and microarray analysis have confirmed that UNC-5 is expressed in DA9 motor neurons. Eight pairs of chemosensory neurons in Caenorhabditis elegans take up fluorescein dyes entering through the chemosensory organs. When filled with dye, the processes and cell bodies of these neurons can be examined in live animals by fluorescence microscopy. Using this technique five genes were identified: unc-33, unc-44, unc-51, unc-76, and unc-106. These genes we found to affect the growth of the amphid and phasmid axons in mutants. There are three phases in hermaphrodite distal tip cell migration in Caenorhabditis elegans which are distinguished by the orientation

neg: Primate basal ganglia of pallidal neurons (only their cell bodies or somata, or trigger points) sending their axons through their particular thalamic territories (or nuclei) to one determined cortical target are organized into radial bands. These were assested to be totally representative of the pallidal organisation. This is certainly not the case. Pallidum is precisely one cerebral place where there is a dramatic change between one afferent geometry and a completely different efferent one. The inmap and the outmap are totally different. This is an indication of the fundamental role of the pallidonigral set: the spatial reorganisation of information for a particular "function",

neg: Cartwheel cell also seen to share other features common to the cerebellar Purkinje cells. Other data supports the structural and functional similarity found between the cartwheel and the Purkinje neuron. Cartwheel cells are shown to have a high density of spines on their dendrites, their axons are myelinated, they are of spherical cell shape and of medium size. The primary targets of the cartwheel cells are the large efferent pyramidal neurons of the DCN, found in layer two. Data retrieved has shown that this targeting of the pyramidal cells modulates their activity and therefore plays a key role in the shaping of

neg: Dorsal nucleus of vagus nerve terminating in the laryngeal, pharyngeal muscles, and musculus uvulae. Dorsal nucleus of vagus nerve The dorsal nucleus of the vagus nerve (or posterior motor nucleus of vagus) is a cranial nerve nucleus for the vagus nerve in the medulla that lies ventral to the floor of the fourth ventricle. It mostly serves parasympathetic vagal functions in the gastrointestinal tract, lungs, and other thoracic and abdominal vagal innervations. The cell bodies for the preganglionic parasympathetic vagal neurons that innervate the heart reside in the nucleus ambiguus. Additional cell bodies are found in the nucleus ambiguus, which give rise to the branchial

neg: Hereditary motor and sensory neuropathy Hereditary motor and sensory neuropathy Hereditary motor and sensory neuropathies (HMSN) is a name sometimes given to a group of different neuropathies which are all characterized by their impact upon both afferent and efferent neural communication. HMSN are characterised by atypical neural development and degradation of neural tissue. The two common forms of HMSN are either hypertrophic demyelinated nerves or complete atrophy of neural tissue. Hypertrophic condition causes neural stiffness and a demyelination of nerves in the peripheral nervous system, and atrophy causes the breakdown of axons and neural cell bodies. In these disorders, a patient experiences progressive muscle atrophy

neg: Spiral ganglion Spiral ganglion The spiral (cochlear) ganglion is the group of nerve cells that serve the sense of hearing by sending a representation of sound from the cochlea to the brain. The cell bodies of the spiral ganglion neurons are found in the modiolus, the conical shaped central axis in the cochlea. Neurons whose cell bodies lie in the spiral ganglion are strung along the bony core of the cochlea, and send fibers (axons) into the central nervous system (CNS). These bipolar neurons are the first neurons in the auditory system to fire an action potential, and supply all of the

neg: Spiral ganglion the central nervous system form the cochlear nerve. Spiral ganglion The spiral (cochlear) ganglion is the group of nerve cells that serve the sense of hearing by sending a representation of sound from the cochlea to the brain. The cell bodies of the spiral ganglion neurons are found in the modiolus, the conical shaped central axis in the cochlea. Neurons whose cell bodies lie in the spiral ganglion are strung along the bony core of the cochlea, and send fibers (axons) into the central nervous system (CNS). These bipolar neurons are the first neurons in the auditory system to fire

neg: Parkinson's disease 70% of the dopamine secreting neurons in the substantia nigra pars compacta by the end of life) and the presence of Lewy bodies (accumulations of the protein alpha-synuclein) in many of the remaining neurons. This loss of neurons is accompanied by the death of astrocytes (star-shaped glial cells) and a significant increase in the number of microglia (another type of glial cell) in the substantia nigra. There are five major pathways in the brain connecting other brain areas with the basal ganglia. These are known as the motor, oculo-motor, associative, limbic and orbitofrontal circuits, with names indicating the main projection

neg: Premovement neuronal activity the basal ganglia. These efferent neurons influence activity of the upper motor neurons. Neurons in these areas are GABAergic, and thus the main output of the basal ganglia is inhibitory, and spontaneous activation of these neurons consistently prevents unwanted movement. The input of medium spiny neurons to these output areas of the basal ganglia are also GABAergic and therefore inhibitory. The net effect of excitatory inputs to the basal ganglia from the cortex is inhibition (via the medium spiny neurons) of the persistently active inhibitory cells in the output center of the basal ganglia. This double inhibitory effect leads to

neg: Nucleus ambiguus Nucleus ambiguus The nucleus ambiguus (literally "ambiguous nucleus") is a group of large motor neurons, situated deep in the medullary reticular formation named by Jacob Clarke. The nucleus ambiguus contains the cell bodies of nerves that innervate the muscles of the soft palate, pharynx, and larynx which are strongly associated with speech and swallowing. As well as motor neurons, the nucleus ambiguus in its "external formation" contains cholinergic preganglionic parasympathetic neurons for the heart. It is a region of histologically disparate cells located just dorsal (posterior) to the inferior olivary nucleus in the lateral portion of the upper (rostral) medulla.

neg: Acetylcholinesterase It has also been shown that the main active ingredient in cannabis, tetrahydrocannabinol, is a competitive inhibitor of acetylcholinesterase. AChE is found in many types of conducting tissue: nerve and muscle, central and peripheral tissues, motor and sensory fibers, and cholinergic and noncholinergic fibers. The activity of AChE is higher in motor neurons than in sensory neurons. Acetylcholinesterase is also found on the red blood cell membranes, where different forms constitute the Yt blood group antigens. Acetylcholinesterase exists in multiple molecular forms, which possess similar catalytic properties, but differ in their oligomeric assembly and mode of attachment to the cell

neg: Unipolar neuron Unipolar neuron A unipolar neuron is a type of neuron in which only one protoplasmic process (neurite) extends from the cell body. Most neurons are multipolar, generating several dendrites and an axon and there are also many bipolar neurons. Unipolar neurons that begin as bipolar neurons during development are known as pseudounipolar neurons. Unipolar neurons are common in insects, where the cell body is often located at the periphery of the brain and is electrically inactive. These cell bodies often send a single neurite into the brain; however, this neurite may ramify into a large number of branches making a

neg: Nerve net nerve net and their placement is highly position specific. Every subset of a neuron has a constant and regional distribution. In a Hydra, cell bodies of epidermal sensory cells are usually found around the mouth at the hypostome's apical tip, neurite's are usually directed down the sides of the hypostome in a radial direction, and ganglion cells are found in the hypostome's basal region (in between tentacles and just below the head). Nerve nets contain intermediate neurons which allow for modulation of neural activity which occurs between the sensation of the stimulus and motor output. Each sensory neuron within a

neg: Shortness of breath central information processing. It is believed the central processing in the brain compares the afferent and efferent signals; and dyspnea results when a "mismatch" occurs between the two: such as when the need for ventilation (afferent signaling) is not being met by physical breathing (efferent signaling). Afferent signals are sensory neuronal signals that ascend to the brain. Afferent neurons significant in dyspnea arise from a large number of sources including the carotid bodies, medulla, lungs, and chest wall. Chemoreceptors in the carotid bodies and medulla supply information regarding the blood gas levels of O, CO and H. In the lungs,

neg: Neuron connections with other cells when it arrives. In most cases, neurons are generated by neural stem cells during brain development and childhood. Neurons in the adult brain generally do not undergo cell division. Astrocytes are star-shaped glial cells that have also been observed to turn into neurons by virtue of the stem cell characteristic pluripotency. Neurogenesis largely ceases during adulthood in most areas of the brain. However, there is strong evidence for generation of substantial numbers of new neurons in two brain areas, the hippocampus and olfactory bulb. A neuron is a specialized type of cell found in the bodies

neg: Renshaw cell proximal muscles of the hand and foot do not have homonymous inhibition. Heteronymous inhibition has been found to be dominant in the leg compared to the arm, where antagonist muscles work simultaneously. (It must also be noted that Renshaw cells are activated by gamma motor neurons, but to a lesser extent). The Renshaw cells not only synapse with homonymous and heteronymous nerves, but also with the Ia interneurones, which are stimulated by the Ia afferents from the same muscle group activated by the motor neurons, which have an inhibitory effect on the antagonist muscle group. This “recurrent facilitation” causes reduced

neg: Lower motor neuron deep tendon reflexes and muscle atrophy. Lower motor neurons are classified based on the type of muscle fiber they innervate: Glutamate released from the upper motor neurons triggers depolarization in the lower motor neurons in the anterior grey column, which in turn causes an action potential to propagate the length of the axon to the neuromuscular junction where acetylcholine is released to carry the signal across the synaptic cleft to the postsynaptic receptors of the muscle cell membrane, signaling the muscle to contract. Damage to lower motor neurons, lower motor neuron lesions (LMNL) cause muscle wasting, decreased strength and decreased

neg: Sensory nerve Sensory nerve A sensory nerve, also called an afferent nerve, is a nerve that carries sensory information toward the central nervous system (CNS). It is a cable-like bundle of the afferent nerve fibers coming from sensory receptors in the peripheral nervous system (PNS). A motor nerve carries information from the CNS to the PNS, and both types of nerve are called peripheral nerves. Afferent nerve fibers link the sensory neurons throughout the body, in pathways to the relevant processing circuits in the central nervous system. Afferent nerve fibers are often paired with efferent nerve fibers from the motor neurons (that

neg: Pioneer neuron intense immunoreactivity for calbindin and calretinin, are characterized by their large size and axonal projection. They remain in the marginal zone after the formation of the cortical plate; they project first into the ventricular zone, and then into the subplate and the internal capsule. Therefore, these cells are the origin of the earliest efferent pathway of the developing cortex. It is thought that axons of pioneer neurons, pioneer axons, serve as a pathway for additional neurons that develop later in the embryo and project their axons to the appropriate target. In many systems pioneer neurons are eliminated by programmed cell-death

neg: Neuroanatomy the sense organs to the CNS, and "efferent" neurons, which carry motor instructions out to the muscles. The autonomic nervous system also has two subdivisions, the sympathetic and the parasympathetic, which are important for regulating the body's basic internal organ functions such as heartbeat, breathing, digestion, and salivation. Autonomic nerves, like somatic nerves, contain afferent and efferent fibers. In anatomy in general and neuroanatomy in particular, several sets of topographic terms are used to denote orientation and location, which are generally referred to the body or brain axis (see Anatomical terms of location). The pairs of terms used most commonly

neg: Peripheral neuropathy the most affected. Diabetic neuropathy is the most common cause of this pattern. In demyelinating polyneuropathies, the myelin sheath around axons is damaged, which affects the ability of the axons to conduct electrical impulses. The third and least common pattern affects the cell bodies of neurons directly. This usually picks out either the motor neurons (known as motor neuron disease) or the sensory neurons (known as "sensory neuronopathy" or "dorsal root ganglionopathy"). The effect of this is to cause symptoms in more than one part of the body, often symmetrically on left and right sides. As for any neuropathy, the

neg: Juxtaglomerular apparatus of both afferent and efferent artriole. The juxtaglomerular apparatus consists of three cell types. They are: Renin is produced by juxtaglomerular cells. These cells are similar to epithelium and are located in the media of the afferent arterioles as they enter the glomeruli. The juxtaglomerular cells secrete renin in response to: Extraglomerular mesangial cells are located in the junction between the afferent and efferent arterioles, but their significance in this location is unknown. Renin is also found in these cells. At the point where the afferent arterioles enter the glomerulus and the efferent arteriole leaves it, the tubule of nephron

neg: Somatic nervous system Somatic nervous system The somatic nervous system (SNS or voluntary nervous system) is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles. The somatic nervous system consists of afferent nerves or sensory nerves, and efferent nerves or motor nerves. Afferent nerves are responsible for relaying sensation from the body to the central nervous system; efferent nerves are responsible for sending out commands from the CNS to the body, stimulating muscle contraction; they include all the non-sensory neurons connected with skeletal muscles and skin. The "a-" of "afferent" and the "e-" of

neg: Neuron thin axon covered by the myelin sheath. Around the cell body is a branching dendritic tree that receives signals from other neurons. The end of the axon has branching terminals (axon terminal) that release neurotransmitters into a gap called the synaptic cleft between the terminals and the dendrites of the next neuron. Most neurons can be anatomically characterized as: Furthermore, some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are: Afferent and efferent also refer generally to neurons that, respectively, bring information to or send information from the brain.

neg: Accommodation reflex by opposing the internal pressure within the elastic lens, keep it relatively flattened. Opposite of fixating on a near object, the ciliary muscle relaxes and the diameter of the lens increases to increase the lens’ size. The tension along the suspensory ligaments is increased to flatten the lens and decrease the curvature and achieve a lower refractive power. Three regions make up the accommodation neural circuit, the afferent limb, the efferent limb and the ocular motor neurons that are between the afferent and efferent limb. Accommodation reflex The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye,

neg: UNC (biology) C. elegans. Netrins are axon guidance molecules that transmit their activity through 2 different receptors. The function of UNC-5 is to repel axons while the other receptor UNC-40 (or DCC:Deleted in Colorectal Cancer) attracts axons to the source of UNC-6 production. Methods such as antibody staining, transgene expression and microarray analysis have confirmed that UNC-5 is expressed in DA9 motor neurons. Eight pairs of chemosensory neurons in Caenorhabditis elegans take up fluorescein dyes entering through the chemosensory organs. When filled with dye, the processes and cell bodies of these neurons can be examined in live animals by fluorescence microscopy. Using

neg: Cellular neuroscience eighty billion neurons. Neurons are diverse with respect to morphology and function. Thus, not all neurons correspond to the stereotypical motor neuron with dendrites and myelinated axons that conduct action potentials. Some neurons such as photoreceptor cells, for example, do not have myelinated axons that conduct action potentials. Other unipolar neurons found in invertebrates do not even have distinguishing processes such as dendrites. Moreover, the distinctions based on function between neurons and other cells such as cardiac and muscle cells are not helpful. Thus, the fundamental difference between a neuron and a nonneuronal cell is a matter of degree. Another

neg: Cellular neuroscience major class of cells found in the nervous system are glial cells. These cells are only recently beginning to receive attention from neurobiologists for being involved not just in nourishment and support of neurons, but also in modulating synapses. For example, Schwann cells, which are a type of glial cell found in the peripheral nervous system, modulate synaptic connections between presynaptic terminals of motor neuron endplates and muscle fibers at neuromuscular junctions. One prominent characteristic of many neurons is excitability. Neurons generate electrical impulses or changes in voltage of two types: graded potentials and action potentials. Graded potentials occur when

neg: Nucleus (neuroanatomy) nuclei. Notable among these are the thalamus and hypothalamus, each of which contains several dozen distinguishable substructures. The medulla and pons also contain numerous small nuclei with a wide variety of sensory, motor, and regulatory functions. In the peripheral nervous system (PNS), a cluster of cell bodies of neurons (homologous to a CNS nucleus) is called a ganglion. The fascicles of nerve fibers in the PNS (homologous to CNS tracts) are called nerves. Nucleus (neuroanatomy) In neuroanatomy, a nucleus (plural form: nuclei) is a cluster of neurons in the central nervous system, located deep within the cerebral hemispheres and brainstem.

neg: Gut–brain axis the parasympathetic (e.g., via the vagus nerve) and sympathetic (e.g., via the prevertebral ganglia) nervous systems. However, vertebrate studies show that when the vagus nerve is severed, the enteric nervous system continues to function. In vertebrates, the enteric nervous system includes efferent neurons, afferent neurons, and interneurons, all of which make the enteric nervous system capable of carrying reflexes in the absence of CNS input. The sensory neurons report on mechanical and chemical conditions. Through intestinal muscles, the motor neurons control peristalsis and churning of intestinal contents. Other neurons control the secretion of enzymes. The enteric nervous system also makes

neg: Enteric nervous system through the parasympathetic (e.g., via the vagus nerve) and sympathetic (e.g., via the prevertebral ganglia) nervous systems. However, vertebrate studies show that when the vagus nerve is severed, the enteric nervous system continues to function. In vertebrates, the enteric nervous system includes efferent neurons, afferent neurons, and interneurons, all of which make the enteric nervous system capable of carrying reflexes and acting as an integrating center in the absence of CNS input. The sensory neurons report on mechanical and chemical conditions. Through intestinal muscles, the motor neurons control peristalsis and churning of intestinal contents. Other neurons control the secretion of

neg: Henneman's size principle four factors, which were consistent with a similar study performed several years prior. In that study, an increase in muscle fiber conduction velocity was observed when there was a higher level of voluntary muscle contraction, which agrees with the gradual recruitment of higher-force muscle types. In Wistar rats, it was found that cell size is the crucial property in determining neuronal recruitment. Motor neurons of different sizes have similar voltage thresholds. Smaller neurons have higher membrane resistance and require lower depolarizing current to reach spike threshold. The cell size contribution to recruitment in motor neurons during postnatal development is investigated

neg: Mauthner cell the activity of smaller motor neurons. In larval zebrafish about ~60% of the total population of reticulospinal neurons are also activated by a stimulus that elicits the M-spike and C-start escape. A well-studied group of these reticulospinal neurons are the bilaterally paired M-cell homologues denoted MiD2cm and MiD3cm. These neurons exhibit morphological similarities to the M-cell including a lateral and ventral dendrite. They are located in rhombomeres 5 and 6 of hindbrain respectively, and also receive auditory input in parallel with the M-cell from the pVIIIth nerve. In fish, water jet stimuli that activate these neurons elicit non-mauthner initiated C-starts

neg: Cerebellar granule cell Cerebellar granule cell Cerebellar granule cells form the thick granular layer of the cerebellar cortex and are among the smallest neurons in the brain. (The term granule cell is used for several unrelated types of small neurons in various parts of the brain.) Cerebellar granule cells are also the most numerous neurons in the brain: in humans, estimates of their total number average around 50 billion, which means that they constitute about 3/4 of the brain's neurons. The cell bodies are packed into a thick granular layer at the bottom of the cerebellar cortex. A granule cell emits only four

neg: Peripherin of peripherin. Per 56 is made by a receptor on exon 9 of the peripherin gene transcript which induces a frameshift and replacement of a 21 amino acid sequence in the C-terminal found on the dominant 57 form with a new 8 amino acid sequence. The functions of these two alternative forms of peripherin are unknown. Per 57 and 56 are normally co-expressed, whereas Per 61 is not found in normal peripherin expression in adult motor neurons. Peripherin is widely expressed in the cell body and axons of neurons in the peripheral nervous system. These include small-sized root ganglion neurons,

neg: Dopaminergic pathways Dopaminergic pathways Dopaminergic pathways, sometimes called dopaminergic projections, are the sets of projection neurons in the brain that synthesize and release the neurotransmitter dopamine. Individual neurons in these pathways are referred to as dopamine neurons. Dopamine neurons have axons that run the entire length of the pathway. The neurons' somata produce the enzymes that synthesize dopamine, and they are then transmitted via the projecting axons to their synaptic destinations, where most of the dopamine is produced. Dopaminergic nerve cell bodies in such areas as the substantia nigra pars compacta tend to be pigmented due to the presence of the black