April 17, 2012
Acetylcholine better known as ACh is a neurotransmitter that is produced by cholinergic neurons. Nerves that rely on Ach are classified as cholinergic nerves. Acetylcholine is found in both the peripheral nervous system and the central nervous system. Acetylcholine can also be found in the autonomic nervous system and is the only neurotransmitter used in motor division of the somatic nervous system. In the peripheral nervous system acetylcholine plays a role in skeletal muscle movement, as well as in the regulation of smooth muscle and cardiac muscle. In the central nervous system acetylcholine is believed to be involved in the sleep-wake cycle, learning, memory, and mood. Acetylcholine is synthesized from choline and acetyl coenzyme A through the action of the enzyme choline acetyltransferase and becomes packaged into membrane-bound vesicles. After the arrival of a nerve signal at the termination of an axon, the vesicles fuse with the cell membrane, causing the release of acetylcholine into the synaptic cleft. Transmission of a nerve signal occurs when a neurotransmitter is released by the presynaptic neuron, crosses the synapse (the place where the tip of a neuron and its target cell lie adjacent to each other), and fits into a receptor on the postynaptic neuron. For the nerve signal to continue, acetylcholine must diffuse to another nearby neuron or muscle cell, where it will bind and activate a receptor protein. When the message is delivered, acetylcholinesterase; which is present in the synaptic cleft, will catalyze the decomposition of acetylcholine. Choline is absorbed back into the presynaptic neuron where new ACh is synthesized in a process called reuptake. A drug is any molecule that alters normal functions when it enters the body from an external source .Pharmacologist classifies drugs as either agonists or antagonists. An agonist is a substance that acts to produce or prolong the...
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