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Spinotectal Tract
The spinomesencephalic pathway, spinomesencephalic tract or spino-quadrigeminal system of Mott, includes a number of ascending tracts in the spinal cord, including the spinotectal tract. The spinomesencephalic tract is one of the ascending tracts in the anterolateral system of the spinal cord that projects to various parts of the midbrain. It is involved in the processing of pain and visceral sensations. In the ALS The anterolateral system (ALS) is a bundle of afferent somatosensory fibers from different ascending tracts in the spinal cord. These fibers include those of the spinomesencephalic tract, spinothalamic tract, and spinoreticular tract amongst others. Spinomesencephalic fibres project to the periaqueductal gray, and to the tectum. Other fibers project to and terminate in the parabrachial nucleus, the pretectum, and the nucleus of Darkschewitsch. The fibers that project to the tectum are known as the spinotectal fibers. The spinotectal tract fibers project to the super ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinal Cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal cord is hollow and contains a structure called the central canal, which contains cerebrospinal fluid. The spinal cord is also covered by meninges and enclosed by the neural arches. Together, the brain and spinal cord make up the central nervous system. In humans, the spinal cord is a continuation of the brainstem and anatomically begins at the occipital bone, passing out of the foramen magnum and then enters the spinal canal at the beginning of the cervical vertebrae. The spinal cord extends down to between the first and second lumbar vertebrae, where it tapers to become the cauda equina. The enclosing bony vertebral column protects the relatively shorter spinal cord. It is around long in adult men and around long in adult women. The diam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superior Colliculus
In neuroanatomy, the superior colliculus () is a structure lying on the tectum, roof of the mammalian midbrain. In non-mammalian vertebrates, the Homology (biology), homologous structure is known as the optic tectum or optic lobe. The adjective form ''tectum, tectal'' is commonly used for both structures. In mammals, the superior colliculus forms a major component of the midbrain. It is a paired structure and together with the paired inferior colliculi forms the corpora quadrigemina. The superior colliculus is a layered structure, with a pattern that is similar in all mammals. The layers can be grouped into the superficial layers (retinal nerve fiber layer, stratum opticum and above) and the deeper remaining layers. Neurons in the superficial layers receive direct input from the retina and respond almost exclusively to visual stimuli. Many neurons in the deeper layers also respond to other modalities, and some respond to stimuli in multiple modalities. The deeper layers also conta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raphespinal Tract
The raphespinal tract is a descending spinal cord tract located in the medulla oblongata. It consists of two tracts an anterior raphespinal tract, and a lateral raphespinal tract that mainly descend in the lateral funiculus. Fibers descend in the ventral portion of the lateral funiculus, mainly bilaterally to terminate in laminae I, II, and IV. The tract emerges from three of the raphe nuclei, the magnus, obscurus, and pallidus. The fibers of the raphespinal tract are mainly serotonergic. When raphe nuclei are stimulated they release serotonin which modulates the transmission of pain. Pathways Pain pathways converging upon the raphe nuclei to modulate pain via the raphespinal tract include: ** Laminae I and V of spinal cord→ spinomesencephalic tract → periaqueductal gray → nucleus raphe magnus → ** Laminae I and V of spinal cord → spinomesencephalic tract → mesencephalon raphe nuclei → ** Nociceptive group C first-order nerve fiber → interneurons of lami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tectospinal Tract
In humans, the tectospinal tract (or colliculospinal tract) is a decussating extrapyramidal tract that coordinates head/neck and eye movements. It arises from the superior colliculus of the mesencephalic (midbrain) tectum, and projects to the cervical and upper thoracic spinal cord levels. It mediates reflex turning of the head and upper trunk in the direction of startling sensory stimuli (visual, auditory, or skin). It arises from the deep layers of the superior colliculus. It decussates within the posterior part of mesencephalic tegmentum at the level of the red nucleus. It descends through the medulla oblongata near the midline within the medial longitudinal fasciculus. In the spinal cord, it descends in the anterior funiculus. It terminates by synapsing with interneurons of the intermediate zone and anterior grey column. See also * Spinotectal tract * Upper motor neuron Upper motor neurons (UMNs) is a term introduced by William Gowers in 1886. They are found in the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ipsilateral
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and axes. The meaning of terms that are used can change depending on whether a vertebrate is a biped or a quadruped, due to the difference in the neuraxis, or if an invertebrate is a non-bilaterian. A non-bilaterian has no anterior or posterior surface for example but can still have a descriptor used such as proximal or distal in relation to a body part that is nearest to, or furthest from its middle. International organisations have determined vocabularies that are often used as standards for subdisciplines of anatomy. For example, '' Terminolog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sensory Decussation
The sensory decussation or decussation of the lemnisci is a decussation (a crossing over) of axons from the gracile nucleus and cuneate nucleus, known together as the dorsal column nuclei. The dorsal column nuclei are responsible for fine touch, vibration, proprioception and two-point discrimination. The fibers of this decussation are called the internal arcuate fibers and are found at the superior aspect of the closed medulla oblongata, superior to the motor decussation. Neurons of these nuclei are second-order neurons in the dorsal column–medial lemniscus pathway. Structure At the level of the closed medulla in the posterior white column, two large nuclei namely the gracile nucleus and the cuneate nucleus can be found. The two nuclei receive the impulse from the two ascending tracts: fasciculus gracilis and fasciculus cuneatus. After the two tracts terminate upon these nuclei, the heavily myelinated fibres arise and ascend anteromedially around the periaqueducta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rexed Lamina
The Rexed laminae (singular: Rexed lamina) comprise a system of ten layers of grey matter (I–X), identified in the early 1950s by Bror Rexed to label portions of the grey columns of the spinal cord. Similar to Brodmann areas, they are defined by their cellular structure rather than by their location, but the location still remains reasonably consistent. Laminae * Posterior grey column: I–VI ** Lamina I: marginal nucleus of spinal cord or posteromarginal nucleus ** Lamina II: substantia gelatinosa of Rolando ** Laminae III and IV: nucleus proprius ** Lamina V: Neck of the dorsal horn. Neurons within lamina V are mainly involved in processing sensory afferent stimuli from cutaneous, muscle and joint mechanical nociceptors as well as visceral nociceptors. This layer is home to wide dynamic range tract neurons, interneurons and propriospinal neurons. Viscerosomatic pain signal convergence often occurs in this lamina due to the presence of wide dynamic range tract neurons ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nociceptive
In physiology, nociception , also nocioception; ) is the sensory nervous system's process of encoding noxious stimuli. It deals with a series of events and processes required for an organism to receive a painful stimulus, convert it to a molecular signal, and recognize and characterize the signal to trigger an appropriate defensive response. In nociception, intense chemical (e.g., capsaicin present in chili pepper or cayenne pepper), mechanical (e.g., cutting, crushing), or thermal (heat and cold) stimulation of sensory neurons called nociceptors produces a signal that travels along a chain of nerve fibers to the brain. Nociception triggers a variety of physiological and behavioral responses to protect the organism against an aggression, and usually results in a subjective experience, or perception, of pain in sentient beings. Detection of noxious stimuli Potentially damaging mechanical, thermal, and chemical stimuli are detected by nerve endings called nociceptors, which are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myelinated
Myelin Sheath ( ) is a lipid-rich material that in most vertebrates surrounds the axons of neurons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. The myelinated axon can be likened to an electrical wire (the axon) with insulating material (myelin) around it. However, unlike the plastic covering on an electrical wire, myelin does not form a single long sheath over the entire length of the axon. Myelin ensheaths part of an axon known as an internodal segment, in multiple myelin layers of a tightly regulated internodal length. The ensheathed segments are separated at regular short unmyelinated intervals, called nodes of Ranvier. Each node of Ranvier is around one micrometre long. Nodes of Ranvier enable a much faster rate of conduction known as saltatory conduction where the action potential recharges at each node to jump over to the next node, and so on till it reaches the axon terminal. At the terminal the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleus Of Darkschewitsch
The nucleus of Darkschewitsch is an accessory oculomotor nucleus situated in the ventrolateral portion of the periaqueductal gray of the mesencephalon (midbrain) near its junction with the diencephalon. It is involved in mediating vertical eye movements. It projects to the trochlear nucleus, receives afferents from the visual cortex, and forms a reciprocal (looping) connection with the cerebellum by way of the inferior olive. Anatomy Connections It receives afferents from the visual association areas (via the corticotectal tract), vestibular nuclei (via the medial longitudinal fasciculus), and from the spinomesencephalic tract. It gives rise to the medial tegmental tract to project efferents to the (rostral portion of) medial accessory olivary nucleus → ((decussation) inferior cerebellar peduncle → (contralateral) globose nucleus of cerebellum → superior cerebellar peduncle (decussation) → (rostral part of) medial accessory olivary nucleus → (ipsilateral) nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nerve Tract
A nerve tract is a bundle of nerve fibers (axons) connecting Nucleus (neuroanatomy), nuclei of the central nervous system. In the peripheral nervous system, this is known as a nerve fascicle, and has associated nervous tissue, connective tissue. The main nerve tracts in the central nervous system are of three types: association fibers, commissural fibers, and projection fibers. A nerve tract may also be referred to as a commissure, decussation, or neural pathway. A commissure connects the two cerebral hemispheres at the same levels, while a decussation connects at different levels (crosses obliquely). Types The nerve fibers in the central nervous system can be categorized into three groups on the basis of their course and connections. Different tracts may also be referred to as ''projections'' or ''radiations'' such as thalamocortical radiations. Association fibers The tracts that connect cortical areas within the same hemisphere are called Association fiber, association tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pretectum
In neuroanatomy, the pretectal area, or pretectum, is a midbrain structure composed of seven nuclei and comprises part of the subcortical visual system. Through reciprocal bilateral projections from the retina, it is involved primarily in mediating behavioral responses to acute changes in ambient light such as the pupillary light reflex, the optokinetic reflex, and temporary changes to the circadian rhythm. In addition to the pretectum's role in the visual system, the anterior pretectal nucleus has been found to mediate somatosensory and nociceptive information. Location and structure The pretectum is a bilateral group of highly interconnected nuclei located near the junction of the midbrain and forebrain. The pretectum is generally classified as a midbrain structure, although because of its proximity to the forebrain it is sometimes classified as part of the caudal diencephalon (forebrain). Within vertebrates, the pretectum is located directly anterior to the superior collicul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
