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Acetylcholine
Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Parts in the body that use or are affected by acetylcholine are referred to as cholinergic. Substances that increase or decrease the overall activity of the cholinergic system are called cholinergics and anticholinergics, respectively. Acetylcholine is the neurotransmitter used at the neuromuscular junction—in other words, it is the chemical that motor neurons of the nervous system release in order to activate muscles. This property means that drugs that affect cholinergic systems can have very dangerous effects ranging from paralysis to convulsions. Acetylcholine is also a neurotransmitter in the autonomic nervous system, both as an internal transmitter for the sympathetic nervous system and as the final product released by the para ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotransmitters are released from synaptic vesicles into the synaptic cleft where they are able to interact with neurotransmitter receptors on the target cell. The neurotransmitter's effect on the target cell is determined by the receptor it binds. Many neurotransmitters are synthesized from simple and plentiful precursors such as amino acids, which are readily available and often require a small number of biosynthetic steps for conversion. Neurotransmitters are essential to the function of complex neural systems. The exact number of unique neurotransmitters in humans is unknown, but more than 100 have been identified. Common neurotransmitters include glutamate, GABA, acetylcholine, glycine and norepinephrine. Mechanism and cycle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetylcholinesterase Inhibitor
Acetylcholinesterase inhibitors (AChEIs) also often called cholinesterase inhibitors, inhibit the enzyme acetylcholinesterase from breaking down the neurotransmitter acetylcholine into choline and acetate, thereby increasing both the level and duration of action of acetylcholine in the central nervous system, autonomic ganglia and neuromuscular junctions, which are rich in acetylcholine receptors. Acetylcholinesterase inhibitors are one of two types of cholinesterase inhibitors; the other being butyryl-cholinesterase inhibitors. Acetylcholinesterase is the primary member of the cholinesterase enzyme family. Acetylcholinesterase inhibitors are classified as reversible, irreversible, or quasi-irreversible (also called pseudo-irreversible). Mechanism of action Organophosphates Organophosphates like TEPP and sarin inhibit cholinesterases, enzymes that hydrolyze the neurotransmitter acetylcholine. The active centre of cholinesterases feature two important sites, namely t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetylcholinesterase
Acetylcholinesterase (HGNC symbol ACHE; EC 3.1.1.7; systematic name acetylcholine acetylhydrolase), also known as AChE, AChase or acetylhydrolase, is the primary cholinesterase in the body. It is an enzyme that catalyzes the breakdown of acetylcholine and some other choline esters that function as neurotransmitters: : acetylcholine + H2O = choline + acetate It is found at mainly neuromuscular junctions and in chemical synapses of the cholinergic type, where its activity serves to terminate synaptic transmission. It belongs to the carboxylesterase family of enzymes. It is the primary target of inhibition by organophosphorus compounds such as nerve agents and pesticides. Enzyme structure and mechanism AChE is a hydrolase that hydrolyzes choline esters. It has a very high catalytic activity—each molecule of AChE degrades about 25,000 molecules of acetylcholine (ACh) per second, approaching the limit allowed by diffusion of the substrate. The active site of AChE comprises 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nicotinic Acetylcholine Receptor
Nicotinic acetylcholine receptors, or nAChRs, are receptor polypeptides that respond to the neurotransmitter acetylcholine. Nicotinic receptors also respond to drugs such as the agonist nicotine. They are found in the central and peripheral nervous system, muscle, and many other tissues of many organisms. At the neuromuscular junction they are the primary receptor in muscle for motor nerve-muscle communication that controls muscle contraction. In the peripheral nervous system: (1) they transmit outgoing signals from the presynaptic to the postsynaptic cells within the sympathetic and parasympathetic nervous system, and (2) they are the receptors found on skeletal muscle that receive acetylcholine released to signal for muscular contraction. In the immune system, nAChRs regulate inflammatory processes and signal through distinct intracellular pathways. In insects, the cholinergic system is limited to the central nervous system. The nicotinic receptors are considered choline ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muscarinic Acetylcholine Receptor
Muscarinic acetylcholine receptors, or mAChRs, are acetylcholine receptors that form G protein-coupled receptor, G protein-coupled receptor complexes in the cell membranes of certain neurons and other Cell (biology), cells. They play several roles, including acting as the main end-receptor stimulated by acetylcholine released from postganglionic fibers in the parasympathetic nervous system. Muscarinic receptors are so named because they are more sensitive to muscarine than to nicotine. Their counterparts are nicotinic acetylcholine receptors (nAChRs), receptor ion channels that are also important in the autonomic nervous system. Many drugs and other substances (for example pilocarpine and Hyoscine hydrobromide, scopolamine) manipulate these two distinct receptors by acting as selective agonists or receptor antagonist, antagonists. Function acetylcholine, Acetylcholine (ACh) is a neurotransmitter found in the brain, neuromuscular junctions and the autonomic ganglia. Muscarini ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Choline Acetyltransferase
Choline acetyltransferase (commonly abbreviated as ChAT, but sometimes CAT) is a transferase enzyme responsible for the synthesis of the neurotransmitter acetylcholine. ChAT catalyzes the transfer of an acetyl group from the coenzyme acetyl-CoA to choline, yielding acetylcholine (ACh). ChAT is found in high concentration in cholinergic neurons, both in the central nervous system (CNS) and peripheral nervous system (PNS). As with most nerve terminal proteins, ChAT is produced in the body of the neuron and is transported to the nerve terminal, where its concentration is highest. Presence of ChAT in a nerve cell classifies this cell as a "cholinergic" neuron. In humans, the choline acetyltransferase enzyme is encoded by the ''CHAT'' gene. History Choline acetyltransferase was first described by David Nachmansohn and A. L. Machado in 1943. A German biochemist, Nachmansohn had been studying the process of nerve impulse conduction and utilization of energy-yielding chemical reacti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Choline
Choline is an essential nutrient for humans and many other animals. Choline occurs as a cation that forms various salts (X− in the depicted formula is an undefined counteranion). Humans are capable of some ''de novo synthesis'' of choline but require additional choline in the diet to maintain health. Dietary requirements can be met by choline per se or in the form of choline phospholipids, such as phosphatidylcholine. Choline is not formally classified as a vitamin despite being an essential nutrient with an amino acid–like structure and metabolism. In most animals, choline phospholipids are necessary components in cell membranes, in the membranes of cell organelles, and in very low-density lipoproteins. Choline is required to produce acetylcholine – a neurotransmitter – and ''S''-adenosylmethionine (SAM), a universal methyl donor. Upon methylation SAM is transformed into homocysteine. Symptomatic choline deficiency causes non-alcoholic fatty liver disease and muscl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sarin
Sarin (NATO designation GB G-series, "B"">Nerve_agent#G-series.html" ;"title="hort for Nerve agent#G-series">G-series, "B" is an extremely toxic synthetic organophosphorus compound.Sarin (GB) Emergency Response Safety and Health Database. National Institute for Occupational Safety and Health. Accessed April 20, 2009. A colourless, odourless , it is used as a due to its extreme potency as a . Exposure is lethal even at very low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nerve Agent
Nerve agents, sometimes also called nerve gases, are a class of organic chemicals that disrupt the mechanisms by which nerves transfer messages to organs. The disruption is caused by the blocking of acetylcholinesterase (AChE), an enzyme that catalyzes the breakdown of acetylcholine, a neurotransmitter. Nerve agents are acetylcholinesterase inhibitors used as poison. Poisoning by a nerve agent leads to constriction of pupils, profuse salivation, convulsions, and involuntary urination and defecation, with the first symptoms appearing in seconds after exposure. Death by asphyxiation or cardiac arrest may follow in minutes due to the loss of the body's control over respiratory and other muscles. Some nerve agents are readily vaporized or aerosolized, and the primary portal of entry into the body is the respiratory system. Nerve agents can also be absorbed through the skin, requiring that those likely to be subjected to such agents wear a full body suit in addition to a respirator. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cholinergic
Cholinergic agents are compounds which mimic the action of acetylcholine and/or butyrylcholine. In general, the word "choline" describes the various quaternary ammonium salts containing the ''N'',''N'',''N''-trimethylethanolammonium cation. Found in most animal tissues, choline is a primary component of the neurotransmitter acetylcholine and functions with inositol as a basic constituent of lecithin. Choline also prevents fat deposits in the liver and facilitates the movement of fats into cells. The parasympathetic nervous system, which uses acetylcholine almost exclusively to send its messages, is said to be almost entirely cholinergic. Neuromuscular junctions, preganglionic neurons of the sympathetic nervous system, the basal forebrain, and brain stem complexes are also cholinergic, as are the receptor for the merocrine sweat glands. In neuroscience and related fields, the term cholinergic is used in these related contexts: * A substance (or ligand) is cholinergic i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motor Neuron
A motor neuron (or motoneuron or efferent neuron) 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 spinal cord to the effectors. Types of lower motor neurons are alpha motor neurons, beta motor neurons, and gamma motor neurons. A single motor neuron may innervate many muscle fibres and a muscle fibre can undergo many action potentials in the time taken for a single muscle twitch. Innervation takes place at a neuromuscular junction and twitches can become superimposed as a resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nicotine
Nicotine is a naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and '' Duboisia hopwoodii'') and is widely used recreationally as a stimulant and anxiolytic. As a pharmaceutical drug, it is used for smoking cessation to relieve withdrawal symptoms. Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs), except at two nicotinic receptor subunits ( nAChRα9 and nAChRα10) where it acts as a receptor antagonist. Nicotine constitutes approximately 0.6–3.0% of the dry weight of tobacco. Nicotine is also present at ppb-concentrations in edible plants in the family Solanaceae, including potatoes, tomatoes, and eggplants, though sources disagree on whether this has any biological significance to human consumers. It functions as an antiherbivore toxin; consequently, nicotine was widely used as an insecticide in the past, and neonicotinoids (structurally similar to nicotine), such as imidaclopri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
