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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 .
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. In the neuromuscular system, nerves from the central nervous system and the peripheral nervous system are linked and work together with muscles. [3]
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.
The α 2, on the other hand, couples to G i, which causes a decrease in neurotransmitter release, as well as a decrease of cAMP activity resulting in smooth muscle contraction. The β receptor couples to G s and increases intracellular cAMP activity, resulting in e.g. heart muscle contraction, smooth muscle relaxation and glycogenolysis. There ...
Vasoconstriction of arteries to heart (coronary artery); [10] however, the extent of this effect may be limited and may be negated by the vasodilatory effect from β 2 receptors [11] Constriction of some vascular smooth muscle [12] Venoconstriction of veins [13] Decrease motility of smooth muscle in gastrointestinal tract [14] Inhibition of ...
The two main myofilaments in cardiac (and skeletal) muscle are actin and myosin. Ca 2+ binds to a protein called troponin , which is bound to the actin filament. This binding causes a shape change in the troponin which exposes areas on the actin , to which the head of the myosin filament binds.
They are located in the smooth muscles of the blood vessels, as well as in the lungs. Because the M 3 receptor is G q-coupled and mediates an increase in intracellular calcium, it typically causes contraction of smooth muscle, such as that observed during bronchoconstriction and bladder voiding. [32]
Molecular biology has shown that the nicotinic and muscarinic receptors belong to distinct protein superfamilies.Nicotinic receptors are of two types: Nm and Nn. Nm [1] is located in the neuromuscular junction which causes the contraction of skeletal muscles by way of end-plate potential (EPPs).