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Clarke's Column
The posterior thoracic nucleus, (Clarke's column, column of Clarke, dorsal nucleus, nucleus dorsalis of Clarke) is a group of interneurons found in the medial part of lamina VII, also known as the intermediate zone, of the spinal cord. It is mainly located from the cervical vertebra C7 to lumbar L3–L4 levels and is an important structure for proprioception of the lower limb. Anatomy It occupies the medial part of the base of the posterior grey column and appears on the transverse section as a well-defined oval area. It begins caudally at the level of the second or third lumbar nerve, and reaches its maximum size opposite the twelfth thoracic nerve. Above the level of the eight thoracic nerve its size diminishes, and the column ends opposite the last cervical or first thoracic nerve. It is represented, however, in the other regions by scattered cells, which become aggregated to form a cervical nucleus opposite the third cervical nerve, and a sacral nucleus in the middle and low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Posterior Root
The dorsal root of spinal nerve (or posterior root of spinal nerve or sensory root) is one of two "roots" which emerge from the spinal cord. It emerges directly from the spinal cord, and travels to the dorsal root ganglion. Nerve fibres with the Ventral root of spinal nerve, ventral root then combine to form a spinal nerve. The dorsal root transmits sensory information, forming the afferent nerve, afferent somatosensory system, sensory root of a spinal nerve. Structure The root emerges from the Anatomical terms of location, posterior part of the spinal cord and travels to the dorsal root ganglion. The dorsal root ganglia contain the pseudounipolar neuron, pseudo-unipolar Perikaryon, cell bodies of the nerve fibres which travel from the ganglia through the root into the spinal cord. The Anatomical terms of location#Left and right .28lateral.29.2C and medial, lateral division of the dorsal root contains lightly myelinated and unmyelinated fibres of small diameter. These carry pain a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mossy Fiber (cerebellum)
Mossy fibers are one of the major inputs to cerebellum. There are many sources of this pathway, the largest of which is the cerebral cortex, which sends input to the cerebellum via the pontocerebellar pathway. Other contributors include the vestibular nerve and nuclei, the spinal cord, the reticular formation, and feedback from deep cerebellar nuclei. Axons enter the cerebellum via the middle and inferior cerebellar peduncles, where some branch to make contact with deep cerebellar nuclei. They ascend into the white matter of the cerebellum, where each axon branches to innervate granule cells in several cerebellar folia. In this case, the pathway is so named for a unique synapse formed by its projections, the ''mossy fiber rosette''. Fine branches of the mossy fiber axons twist through the granule cell layer, and slight enlargements giving a knotted appearance indicate synaptic contacts. These contacts have the appearance of a classic Gray's type 1 synapse, indicating they are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dysarthria
Dysarthria is a speech sound disorder resulting from neurological injury of the motor component of the motor–speech system and is characterized by poor articulation of phonemes. In other words, it is a condition in which problems effectively occur with the muscles that help produce speech, often making it very difficult to pronounce words. It is unrelated to problems with understanding language (that is, dysphasia or aphasia), although a person can have both. Any of the speech subsystems (respiration, phonation, resonance, prosody, and articulation) can be affected, leading to impairments in intelligibility, audibility, naturalness, and efficiency of vocal communication. Dysarthria that has progressed to a total loss of speech is referred to as anarthria. The term ''dysarthria'' is from New Latin, ''dys-'' "dysfunctional, impaired" and ''arthr-'' "joint, vocal articulation". Neurological injury due to damage in the central or peripheral nervous system may result in weakness ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friedreich's Ataxia
Friedreich's ataxia (FRDA or FA) is an autosomal-recessive genetic disease that causes difficulty walking, a loss of sensation in the arms and legs, and impaired speech that worsens over time. Symptoms generally start between 5 and 20 years of age. Many develop hypertrophic cardiomyopathy and require a mobility aid such as a cane, walker, or wheelchair in their teens. As the disease progresses, some affected people lose their sight and hearing. Other complications may include scoliosis and diabetes mellitus. The condition is caused by mutations in the ''FXN'' gene on chromosome 9, which makes a protein called frataxin. In FRDA, cells produce less frataxin. Degeneration of nerve tissue in the spinal cord causes the ataxia; particularly affected are the sensory neurons essential for directing muscle movement of the arms and legs through connections with the cerebellum. The spinal cord becomes thinner, and nerve cells lose some myelin sheath. No effective treatment is kn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dorsal Spinocerebellar Tract
The spinocerebellar tract is a nerve tract originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum. Origins of proprioceptive information Proprioceptive information is obtained by Golgi tendon organs and muscle spindles. * Golgi tendon organs consist of a fibrous capsule enclosing tendon fascicles and bare nerve endings that respond to tension in the tendon by causing action potentials in type Ib afferents. These fibers are relatively large, myelinated, and quickly conducting. * Muscle spindles monitor the length within muscles and send information via faster Ia afferents. These axons are larger and faster than type Ib (from both nuclear bag fibers and nuclear chain fibers) and type II afferents (solely from nuclear chain fibers). All of these neurons are sensory (first order, or primary) and have their cell bodies in the dorsal root ganglia. They pass through Rexed laminae layers I-VI of the posterior grey column (dorsal horn) to form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cerebellar Cortex
The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebellum plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language as well as emotional control such as regulating fear and pleasure responses, but its movement-related functions are the most solidly established. The human cerebellum does not initiate movement, but contributes to coordination, precision, and accurate timing: it receives input from sensory systems of the spinal cord and from other parts of the brain, and integrates these inputs to fine-tune motor activity. Cerebellar damage produces disorders in fine movement, equilibrium, posture, and motor learning in humans. Anatomically, the human cerebellum has the appearance of a separate structure attached to the bottom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tendon Organ
The Golgi tendon organ (GTO) (also called Golgi organ, tendon organ, neurotendinous organ or neurotendinous spindle) is a proprioceptor – a type of sensory receptor that senses changes in muscle tension. It lies at the interface between a muscle and its tendon known as the musculotendinous junction also known as the myotendinous junction. It provides the sensory component of the Golgi tendon reflex. The Golgi tendon organ is one of several eponymous terms named after the Italian physician Camillo Golgi. Structure The body of the Golgi tendon organ is made up of braided strands of collagen (intrafusal fasciculi) that are less compact than elsewhere in the tendon and are encapsulated. The capsule is connected in series (along a single path) with a group of muscle fibers () at one end, and merge into the tendon proper at the other. Each capsule is about long, has a diameter of about , and is perforated by one or more afferent type Ib sensory nerve fibers ( Aɑ fiber), which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muscle Spindle
Muscle spindles are stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers. This information can be processed by the brain as proprioception. The responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, for example, by activating motor neurons via the stretch reflex to resist muscle stretch. The muscle spindle has both sensory and motor components. * Sensory information conveyed by primary type Ia sensory fibers which spiral around muscle fibres within the spindle, and secondary type II sensory fibers * Activation of muscle fibres within the spindle by up to a dozen gamma motor neurons and to a lesser extent by one or two beta motor neurons Structure Muscle spindles are found within the belly of a skeletal muscle. Muscle spindles are fusiform (spindle-shaped), and the spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ventral Spinocerebellar Tract
The spinocerebellar tract is a nerve tract originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum. Origins of proprioceptive information Proprioceptive information is obtained by Golgi tendon organs and muscle spindles. * Golgi tendon organs consist of a fibrous capsule enclosing tendon fascicles and bare nerve endings that respond to tension in the tendon by causing action potentials in type Ib afferents. These fibers are relatively large, myelinated, and quickly conducting. * Muscle spindles monitor the length within muscles and send information via faster Ia afferents. These axons are larger and faster than type Ib (from both nuclear bag fibers and nuclear chain fibers) and type II afferents (solely from nuclear chain fibers). All of these neurons are sensory (first order, or primary) and have their cell bodies in the dorsal root ganglia. They pass through Rexed laminae layers I-VI of the posterior grey column (dorsal horn) to form s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lateral Funiculus
The most lateral of the bundles of the anterior nerve roots is generally taken as a dividing line that separates the anterolateral system into two parts. These are the anterior funiculus, between the anterior median fissure and the most lateral of the anterior nerve roots, and the lateral funiculus (or lateral column) between the exit of these roots and the posterolateral sulcus. The lateral funiculus transmits the contralateral corticospinal and spinothalamic tracts. A lateral cutting of the spinal cord results in the transection of both ipsilateral posterior column and lateral funiculus and this produces Brown-Séquard syndrome Brown-Séquard syndrome (also known as Brown-Séquard's hemiplegia, Brown-Séquard's paralysis, hemiparaplegic syndrome, hemiplegia et hemiparaplegia spinalis, or spinal hemiparaplegia) is caused by damage to one half of the spinal cord, i.e. hem ....Kaplan Qbook - USMLE Step 1 - 5th edition - page References Central nervous system {{ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinocerebellar Tract
The spinocerebellar tract is a nerve tract originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum. Origins of proprioceptive information Proprioceptive information is obtained by Golgi tendon organs and muscle spindles. * Golgi tendon organs consist of a fibrous capsule enclosing tendon fascicles and bare nerve endings that respond to tension in the tendon by causing action potentials in type Ib afferents. These fibers are relatively large, myelinated, and quickly conducting. * Muscle spindles monitor the length within muscles and send information via faster Ia afferents. These axons are larger and faster than type Ib (from both nuclear bag fibers and nuclear chain fibers) and type II afferents (solely from nuclear chain fibers). All of these neurons are sensory (first order, or primary) and have their cell bodies in the dorsal root ganglia. They pass through Rexed laminae layers I-VI of the posterior grey column (dorsal horn) to form s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Efferent Fibers
Efferent nerve fibers refer to axonal projections that ''exit'' a particular region; as opposed to afferent projections that ''arrive'' at the region. These terms have a slightly different meaning in the context of the peripheral nervous system (PNS) and central nervous system (CNS). The efferent fiber is a long process projecting far from the neuron's body that carries nerve impulses away from the central nervous system toward the peripheral effector organs (mainly muscles and glands). A bundle of these fibers is called an efferent nerve (if it connects to muscles, then it is a motor nerve). The opposite direction of neural activity is afferent 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 projection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
