|
Periaqueductal Gray
The periaqueductal gray (PAG, also known as the central gray) is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for descending pain modulation. It has enkephalin-producing cells that suppress pain. The periaqueductal gray is the gray matter located around the cerebral aqueduct within the tegmentum of the midbrain. It projects to the nucleus raphe magnus, and also contains descending autonomic tracts. The ascending pain and temperature fibers of the spinothalamic tract send information to the PAG via the spinomesencephalic tract (so-named because the fibers originate in the spine and terminate in the PAG, in the mesencephalon or midbrain). This region has been used as the target for brain-stimulating implants in patients with chronic pain. Role in analgesia Stimulation of the periaqueductal gray matter of the midbrain activates enkephalin-releasing ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superior Colliculus
In neuroanatomy, the superior colliculus () is a structure lying on the roof of the mammalian midbrain. In non-mammalian vertebrates, the homologous structure is known as the optic tectum, or optic lobe. The adjective form ''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 to all mammals. The layers can be grouped into the superficial layers ( 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 contain a population of motor-related neurons, capable of activat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lentiform Nucleus
The lentiform nucleus, or lenticular nucleus, comprises the putamen and the globus pallidus within the basal ganglia. With the caudate nucleus, it forms the dorsal striatum. It is a large, lens-shaped mass of gray matter just lateral to the internal capsule. Structure When divided horizontally, it exhibits, to some extent, the appearance of a biconvex lens, while a coronal section of its central part presents a somewhat triangular outline. It is shorter than the caudate nucleus and does not extend as far forward. Boundaries It is lateral to the caudate nucleus and thalamus, and is seen only in sections of the hemisphere. It is bounded laterally by a lamina of white substance called the external capsule, and lateral to this is a thin layer of gray substance termed the claustrum. Its anterior end is continuous with the lower part of the head of the caudate nucleus and with the anterior perforated substance. Components In a coronal section through the middle of the lentiform nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinomesencephalic Tract
The spinotectal tract (spinomesencephalic tract, spinotectal fasciculus, spino-quadrigeminal system of Mott) arises in the spinothalamic tract and terminates in the inferior and superior colliculi. It is situated ventral to the lateral spinothalamic tract, but its fibers are more or less intermingled with it. In the brainstem the fibers run lateral from the inferior olive, ventro-lateral from the superior olive, then ventro-medial from the spinal tract of the trigeminal; the fibers come to lie in the medial portion of the lateral lemniscus. See also * Tectospinal tract In humans, the tectospinal tract (or colliculospinal tract) is a nerve tract that coordinates head and eye movements. This tract is part of the extrapyramidal system and connects the midbrain tectum, and cervical regions of the spinal cord. It ... References External links Diagram and overview at uchicago.edu Central nervous system pathways Sensory systems {{Neuroanatomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinothalamic Tract
The spinothalamic tract is a part of the anterolateral system or the ventrolateral system, a sensory pathway to the thalamus. From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory cortex of the postcentral gyrus. The spinothalamic tract consists of two adjacent pathways: anterior and lateral. The anterior spinothalamic tract carries information about crude touch. The lateral spinothalamic tract conveys pain and temperature. In the spinal cord, the spinothalamic tract has somatotopic arrangement, somatotopic organization. This is the segmental organization of its Neck, cervical, thoracic, lumbar, and Sacrum, sacral components, which is arranged from most medial to most lateral respectively. The pathway crosses over (decussates) at the level of the spinal cord, rather than in the brainstem like the dorsal column-medial lemniscus pathway and lateral corticospinal tract. It is one of the three tracts which make up the an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleus Raphe Magnus
Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucleus may also refer to: Science, technology, and mathematics Astronomy *Active galactic nucleus in astronomy *Comet nucleus, the solid, central part of a comet Biology *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA *Nucleus (neuroanatomy), a cluster of cell bodies of neurons in the central nervous system *Nucleus that forms in the eye in nuclear sclerosis (early cataracts) *''Nucleus'', a scientific journal concerned with the cell nucleus; published by Taylor & Francis *Nucleus, a small colony of honeybees, induced to raise a new queen by the beekeeper Computer systems * Nucleus (operating system), sometimes a synonym for kernel * Nucleus CMS, a weblog system * Nucleus RTOS, a real-time operat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Midbrain
The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek ''mesos'', "middle", and ''enkephalos'', "brain". Structure The principal regions of the midbrain are the tectum, the cerebral aqueduct, tegmentum, and the cerebral peduncles. Rostrally the midbrain adjoins the diencephalon (thalamus, hypothalamus, etc.), while caudally it adjoins the hindbrain (pons, medulla and cerebellum). In the rostral direction, the midbrain noticeably splays laterally. Sectioning of the midbrain is usually performed axially, at one of two levels – that of the superior colliculi, or that of the inferior colliculi. One common technique for remembering the structures of the midbrain involves visualizing these cross-sections (especially at the level of the superior colliculi) as the upside-down face of a be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cerebral Aqueduct
The cerebral aqueduct (aqueductus mesencephali, mesencephalic duct, sylvian aqueduct or aqueduct of Sylvius) is a conduit for cerebrospinal fluid (CSF) that connects the third ventricle to the fourth ventricle of the ventricular system of the brain. It is located in the midbrain dorsal to the pons and ventral to the cerebellum. The cerebral aqueduct is surrounded by an enclosing area of gray matter called the periaqueductal gray, or central gray. It was first named after Franciscus Sylvius. Structure Development The cerebral aqueduct, as other parts of the ventricular system of the brain, develops from the central canal of the neural tube, and it originates from the portion of the neural tube that is present in the developing mesencephalon, hence the name "mesencephalic duct." Function The cerebral aqueduct acts like a canal that passes through the midbrain. It connects the third ventricle with the fourth ventricle so that cerebrospinal fluid (CSF) moves between the cereb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grey Matter
Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is distinguished from white matter in that it contains numerous cell bodies and relatively few myelinated axons, while white matter contains relatively few cell bodies and is composed chiefly of long-range myelinated axons. The colour difference arises mainly from the whiteness of myelin. In living tissue, grey matter actually has a very light grey colour with yellowish or pinkish hues, which come from capillary blood vessels and neuronal cell bodies. Structure Grey matter refers to unmyelinated neurons and other cells of the central nervous system. It is present in the brain, brainstem and cerebellum, and present throughout the spinal cord. Grey matter is distributed at the surface of the cerebral hemispheres (cerebral cortex) and of the cerebellu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enkephalin
An enkephalin is a pentapeptide involved in regulating nociception in the body. The enkephalins are termed endogenous ligands, as they are internally derived and bind to the body's opioid receptors. Discovered in 1975, two forms of enkephalin have been found, one containing leucine ("leu"), and the other containing methionine ("met"). Both are products of the proenkephalin gene. * Met-enkephalin is Tyr-Gly-Gly-Phe-Met. * Leu-enkephalin has Tyr-Gly-Gly-Phe-Leu. Endogenous opioid peptides There are three well-characterized families of opioid peptides produced by the body: enkephalins, B-endorphin, and dynorphins. The met-enkephalin peptide sequence is coded for by the enkephalin gene; the leu-enkephalin peptide sequence is coded for by both the enkephalin gene and the dynorphin gene. The proopiomelanocortin gene (POMC) also contains the met-enkephalin sequence on the N-terminus of beta-endorphin, but the endorphin peptide is not processed into enkephalin. Effects on stress ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pain
Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage." In medical diagnosis, pain is regarded as a symptom of an underlying condition. Pain motivates the individual to withdraw from damaging situations, to protect a damaged body part while it heals, and to avoid similar experiences in the future. Most pain resolves once the noxious stimulus is removed and the body has healed, but it may persist despite removal of the stimulus and apparent healing of the body. Sometimes pain arises in the absence of any detectable stimulus, damage or disease. Pain is the most common reason for physician consultation in most developed countries. It is a major symptom in many medical conditions, and can interfere with a person's quality of life and general functioning. Simple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motivation
Motivation is the reason for which humans and other animals initiate, continue, or terminate a behavior at a given time. Motivational states are commonly understood as forces acting within the agent that create a disposition to engage in goal-directed behavior. It is often held that different mental states compete with each other and that only the strongest state determines behavior. This means that we can be motivated to do something without actually doing it. The paradigmatic mental state providing motivation is desire. But various other states, such as beliefs about what one ought to do or intentions, may also provide motivation. Motivation is derived from the word 'motive', which denotes a person's needs, desires, wants, or urges. It is the process of motivating individuals to take action in order to achieve a goal. The psychological elements fueling people's behavior in the context of job goals might include a desire for money. Various competing theories have been proposed co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autonomic Nervous System
The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the peripheral nervous system that supplies viscera, internal organs, smooth muscle and glands. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, its force of contraction, digestion, respiratory rate, pupillary dilation, pupillary response, Micturition, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response. The autonomic nervous system is regulated by integrated reflexes through the brainstem to the spinal cord and organ (anatomy), organs. Autonomic functions include control of respiration, heart rate, cardiac regulation (the cardiac control center), vasomotor activity (the vasomotor center), and certain reflex, reflex actions such as coughing, sneezing, swallowing and vomiting. Those are then subdivided into other areas and are also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
