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Pain Receptor
A nociceptor ("pain receptor" from Latin ''nocere'' 'to harm or hurt') is a sensory neuron that responds to damaging or potentially damaging stimuli by sending "possible threat" signals to the spinal cord and the brain. The brain creates the sensation of pain to direct attention to the body part, so the threat can be mitigated; this process is called nociception. History Nociceptors were discovered by Charles Scott Sherrington in 1906. In earlier centuries, scientists believed that animals were like mechanical devices that transformed the energy of sensory stimuli into motor responses. Sherrington used many different experiments to demonstrate that different types of stimulation to an afferent nerve fiber's receptive field led to different responses. Some intense stimuli trigger reflex withdrawal, certain autonomic responses, and pain. The specific receptors for these intense stimuli were called nociceptors. Location In mammals, nociceptors are found in any area of the body ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Nerve Ending
A free nerve ending (FNE) or bare nerve ending, is an unspecialized, afferent nerve fiber sending its signal to a sensory neuron. ''Afferent'' in this case means bringing information from the body's periphery toward the brain. They function as cutaneous nociceptors and are essentially used by vertebrates to detect noxious stimuli that often result in pain. Structure Free nerve endings are unencapsulated and have no complex sensory structures. They are the most common type of nerve ending, and are most frequently found in the skin. They penetrate the dermis and end in the stratum granulosum. FNEs infiltrate the middle layers of the dermis and surround hair follicles. Types Free nerve endings have different rates of adaptation, stimulus modalities, and fiber types. Rate of adaptation Different types of FNE can be rapidly adapting, intermediate adapting, or slowly adapting. A delta type II fibers are fast-adapting while A delta type I and C fibers are slowly adapting.Rolf-Detlef ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dorsal Root Ganglia
A dorsal root ganglion (or spinal ganglion; also known as a posterior root ganglion) is a cluster of neurons (a ganglion) in a dorsal root of a spinal nerve. The cell bodies of sensory neurons known as first-order neurons are located in the dorsal root ganglia. The axons of dorsal root ganglion neurons are known as afferents. In the peripheral nervous system, afferents refer to the axons that relay sensory information into the central nervous system (i.e. the brain and the spinal cord). Structure The neurons comprising the dorsal root ganglion are of the pseudo-unipolar type, meaning they have a cell body (soma) with two branches that act as a single axon, often referred to as a ''distal process'' and a ''proximal process''. Unlike the majority of neurons found in the central nervous system, an action potential in posterior root ganglion neuron may initiate in the ''distal process'' in the periphery, bypass the cell body, and continue to propagate along the ''proximal pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetanus
Tetanus, also known as lockjaw, is a bacterial infection caused by ''Clostridium tetani'', and is characterized by muscle spasms. In the most common type, the spasms begin in the jaw and then progress to the rest of the body. Each spasm usually lasts a few minutes. Spasms occur frequently for three to four weeks. Some spasms may be severe enough to fracture bones. Other symptoms of tetanus may include fever, sweating, headache, trouble swallowing, high blood pressure, and a fast heart rate. Onset of symptoms is typically three to twenty-one days following infection. Recovery may take months. About ten percent of cases prove to be fatal. ''C. tetani'' is commonly found in soil, saliva, dust, and manure. The bacteria generally enter through a break in the skin such as a cut or puncture wound by a contaminated object. They produce toxins that interfere with normal muscle contractions. Diagnosis is based on the presenting signs and symptoms. The disease does not spread between pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C Fiber
Group C nerve fibers are one of three classes of nerve fiber in the central nervous system (CNS) and peripheral nervous system (PNS). The C group fibers are unmyelinated and have a small diameter and low conduction velocity, whereas Groups A and B are myelinated. Group C fibers include postganglionic fibers in the autonomic nervous system (ANS), and nerve fibers at the dorsal roots (IV fiber). These fibers carry sensory information. Damage or injury to nerve fibers causes neuropathic pain. Capsaicin activates C fibre vanilloid receptors, giving chili peppers a hot sensation. Structure and anatomy Location C fibers are one class of nerve fiber found in the nerves of the somatic sensory system. They are afferent fibers, conveying input signals from the periphery to the central nervous system. Structure C fibers are unmyelinated unlike most other fibers in the nervous system. This lack of myelination is the cause of their slow conduction velocity, which is on the order of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A Delta Fiber
Group A nerve fibers are one of the three classes of nerve fiber as ''generally classified'' by Erlanger and Gasser. The other two classes are the group B nerve fibers, and the group C nerve fibers. Group A are heavily myelinated, group B are moderately myelinated, and group C are unmyelinated. The other classification is a sensory grouping that uses the terms '' type Ia and type Ib'', '' type II'', ''type III'', and ''type IV'', sensory fibers. Types There are four subdivisions of group A nerve fibers: alpha (α) Aα; beta (β) Aβ; , gamma (γ) Aγ, and delta (δ) Aδ. These subdivisions have different amounts of myelination and axon thickness and therefore transmit signals at different speeds. Larger diameter axons and more myelin insulation lead to faster signal propagation. Group A nerves are found in both motor and sensory pathways. Different sensory receptors are innervated by different types of nerve fibers. Proprioceptors are innervated by type Ia, Ib and II s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Central Nervous System
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all parts of the bodies of bilaterally symmetric and triploblastic animals—that is, all multicellular animals except sponges and diploblasts. It is a structure composed of nervous tissue positioned along the rostral (nose end) to caudal (tail end) axis of the body and may have an enlarged section at the rostral end which is a brain. Only arthropods, cephalopods and vertebrates have a true brain (precursor structures exist in onychophorans, gastropods and lancelets). The rest of this article exclusively discusses the vertebrate central nervous system, which is radically distinct from all other animals. Overview In vertebrates, the brain and spinal cord are both enclosed in the meninges. The meninges provide a barrier to chemicals dissolv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Action Potential
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and in some plant cells. Certain endocrine cells such as pancreatic beta cells, and certain cells of the anterior pituitary gland are also excitable cells. In neurons, action potentials play a central role in cell-cell communication by providing for—or with regard to saltatory conduction, assisting—the propagation of signals along the neuron's axon toward synaptic boutons situated at the ends of an axon; these signals can then connect with other neurons at synapses, or to motor cells or glands. In other types of cells, their main function is to activate intracellular processes. In muscle cells, for example, an action potential is the first step in the chain of events l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noxious Stimuli
A noxious stimulus is a stimulus strong enough to threaten the body’s integrity (i.e. cause damage to tissue). Noxious stimulation induces peripheral afferents responsible for transducing pain (including A-delta and C- nerve fibers, as well as free nerve endings), throughout the nervous system of an organism. The ability to perceive noxious stimuli is a prerequisite for nociception, which itself is a prerequisite for nociceptive pain. A noxious stimulus has been seen to drives nocifensive behavioral responses, which are responses to noxious or painful stimuli. These include reflexive, escape behaviors, to avoid harm to an organism's body. Because of rare genetic conditions that inhibit the ability to perceive physical pain, such acongenital insensitivity to pain and anhydrosis (CIPA) noxious stimulation does not invariably lead to tissue damage. Noxious stimuli can either be mechanical (e.g. pinching or other tissue deformation), chemical (e.g. exposure to acid or irritan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glial Cell Line-derived Neurotrophic Factor
Glial cell line-derived neurotrophic factor (GDNF) is a protein that, in humans, is encoded by the ''GDNF'' gene. GDNF is a small protein that potently promotes the survival of many types of neurons. It signals through GFRα receptors, particularly GFRα1. It is also responsible for the determination of spermatogonia into primary spermatocytes, i.e. it is received by RET proto-oncogene (RET) and by forming gradient with SCF it divides the spermatogonia into two cells. As the result there is retention of spermatogonia and formation of spermatocyte. GDNF family of ligands (GFL) GDNF was discovered in 1991, and is the first member of the GDNF family of ligands (GFL) found. Function GDNF is highly distributed throughout both the peripheral and central nervous system. It can be secreted by astrocytes, oligodendrocytes, Schwann cells, motor neurons, and skeletal muscle during the development and growth of neurons and other peripheral cells. The GDNF gene encodes a highly conserved ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropomyosin Receptor Kinase A
Tropomyosin receptor kinase A (TrkA), also known as high affinity nerve growth factor receptor, neurotrophic tyrosine kinase receptor type 1, or TRK1-transforming tyrosine kinase protein is a protein that in humans is encoded by the ''NTRK1'' gene. This gene encodes a member of the neurotrophic tyrosine kinase receptor (NTKR) family. This kinase is a membrane-bound receptor that, upon neurotrophin binding, phosphorylates itself (autophosphorylation) and members of the MAPK pathway. The presence of this kinase leads to cell differentiation and may play a role in specifying sensory neuron subtypes. Mutations in this gene have been associated with congenital insensitivity to pain with anhidrosis, self-mutilating behaviors, intellectual disability and/or cognitive impairment and certain cancers. Alternate transcriptional splice variants of this gene have been found, but only three have been characterized to date. Function and Interaction with NGF TrkA is the high affinity cataly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nerve Growth Factor
Nerve growth factor (NGF) is a neurotrophic factor and neuropeptide primarily involved in the regulation of growth, maintenance, proliferation, and survival of certain target neurons. It is perhaps the prototypical growth factor, in that it was one of the first to be described. Since it was first isolated by Nobel Laureates Rita Levi-Montalcini and Stanley Cohen in 1956, numerous biological processes involving NGF have been identified, two of them being the survival of pancreatic beta cells and the regulation of the immune system. Structure NGF is initially in a 7S, 130-kDa complex of 3 proteins – Alpha-NGF, Beta-NGF, and Gamma-NGF (2:1:2 ratio) when expressed. This form of NGF is also referred to as proNGF (NGF precursor). The gamma subunit of this complex acts as a serine protease, and cleaves the N-terminal of the beta subunit, thereby activating the protein into functional NGF. The term ''nerve growth factor'' usually refers to the 2.5S, 26-kDa beta subunit of the protein ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanoreceptors
A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are innervated by sensory neurons that convert mechanical pressure into electrical signals that, in animals, are sent to the central nervous system. Vertebrate mechanoreceptors Cutaneous mechanoreceptors Cutaneous mechanoreceptors respond to mechanical stimuli that result from physical interaction, including pressure and vibration. They are located in the skin, like other cutaneous receptors. They are all innervated by Aβ fibers, except the mechanorecepting free nerve endings, which are innervated by Aδ fibers. Cutaneous mechanoreceptors can be categorized by what kind of sensation they perceive, by the rate of adaptation, and by morphology. Furthermore, each has a different receptive field. By sensation *The Slowly Adapting type 1 (SA1) mechanoreceptor, with the Merkel corpuscle end-organ (also known as Merkel discs) detect sustained pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
