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Curare was found to block the stimulant action of nicotine in both innervated and chronically denervated muscles. In 1940, Jenkinson identified tubocurarine as a competitive antagonist of acetylcholine. Curare and tubocurarine had important roles in establishing the concept of specific cholinoceptors in the motor end plate. [3]
The main toxin of curare, d-tubocurarine, occupies the same position on the receptor as ACh with an equal or greater affinity, and elicits no response, making it a competitive antagonist. The antidote for curare poisoning is an acetylcholinesterase (AChE) inhibitor (anti-cholinesterase), such as physostigmine or neostigmine. By blocking ACh ...
It allows efferent signals from the nervous system to contract muscle fibers causing them to contract. In vertebrates, the neuromuscular junction is always excitatory, therefore to stop contraction of the muscle, inhibition must occur at the level of the efferent motor neuron. In other words, the inhibition must occur at the level of the spinal ...
A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. [1] It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. [2] Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
A neuromuscular non-depolarizing agent is a form of neuromuscular blocker that does not depolarize the motor end plate. [8] The quaternary ammonium muscle relaxants belong to this class. Quaternary ammonium muscle relaxants are quaternary ammonium salts used as drugs for muscle relaxation, most commonly in anesthesia.
Muscle relaxation and paralysis can theoretically occur by interrupting function at several sites, including the central nervous system, myelinated somatic nerves, unmyelinated motor nerve terminals, nicotinic acetylcholine receptors, the motor end plate, and the muscle membrane or contractile apparatus.
Signal transmission from nerve to muscle at the motor end plate. The neuromuscular junction is the synapse that is formed between an alpha motor neuron (α-MN) and the skeletal muscle fiber. In order for a muscle to contract, an action potential is first propagated down a nerve until it reaches the axon terminal of the motor neuron.
Muscle fibers are excitable cells stimulated by motor neurons. The motor unit consists of a motor neuron and the many fibers that it makes contact with. A single muscle is stimulated by many motor units. Muscle fibers are subject to depolarization by the neurotransmitter acetylcholine, released by the motor neurons at the neuromuscular ...