【正文】 s business development. Rudy Buttignol, president of the public broadcasting pany in British Columbia, Canada, said his work requires frequent travel to Chengdu and the policy makes the trips easier. Data from the city39。 Carreras. Through his exploitation of the nascent phonograph industry, Caruso is also largely responsible for the sweeping interest in opera of the 1910s and ‘20s. And for this, Stanley Jackson wrote in his bookCaruso, he may never be rivaled, for later tenors could not hope to find themselves in a similarly fortuitous position and thus would most certainly ―find it more difficult to win such universal affection as the bubbly, warmhearted little Neapolitan whose voice soared and sobbed from the first wheezy phonographs to bring a new magic into countless lives.‖ Born in Naples, Italy, in 1873, the third of seven children (early sources erroneously state that he was the 18th of 21), Caruso was raised in squalor. His birthplace, according to Jackson, was a―twostoreyed house, flaky with peeling stucco, [acmodating] several families, who shared a solitary coldwater tap on the landing, and like every other dwelling in that locality it lacked indoor sanitation.‖ As a boy, Caruso received very little formal education。 the adoption of an approach to space in which all parts of the canvas played an equally vital role in the total work。s turbulent yet elegant abstract paintings, which were created by spattering paint on huge canvases placed on the floor, brought abstract expressionism before a hostile public. Willem de Kooning39。 and there are some of each type in the brain. These terms are used because nicotine mimics the action of acetylcholine at nicotinic receptors, whereas muscarine, an alkaloid from the mushroom Amanita muscaria, mimics the action of acetylcholine at the muscarinic receptors. Acetylcholine is the neurotransmitter produced by neurons referred to as cholinergic neurons. 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 learning, memory, and mood. Acetylcholine is synthesized from choline and acetyl coenzyme A through the action of the enzyme choline acetyltransferase and bees packaged into membranebound 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 . 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. There are two main types of cholinergic receptors, nicotinic and muscarinic. Nicotinic receptors are located at synapses between two neurons and at synapses between neurons and skeletal muscle cells. Upon activation a nicotinic receptor acts as a channel for the movement of ions into and out of the neuron, directly resulting in depolarization of the neuron. Muscarinic receptors, located at the synapses of nerves with smooth or cardiac muscle, trigger a chain of chemical events referred to as signal transduction. For a cholinergic neuron to receive another impulse, acetylcholine must be released from the receptor to which it has bound. This will only happen if the concentration of acetylcholine in the synaptic cleft is very low. Low synaptic concentrations of acetylcholine can be maintained via a hydrolysis reaction catalyzed by the enzyme acetylcholinesterase. This enzyme hydrolyzes acetylcholine into acetic acid and choline. If acetylcholinesterase activity is inhibited, the synaptic concentration of acetylcholine will remain higher than normal. If this inhibition is irreversible, as in the case of exposure to many nerve gases and some pesticides, sweating, bronchial constriction, convulsions, paralysis, and possibly death can occur. Although irreversible inhibition is dangerous, beneficial effects may be derived from transient (reversible) inhibition. Drugs that inhibit acetylcholinesterase in a reversible manner have been shown to improve memory in some people with Alzheimer39。 請您刪除一下內(nèi)容， O(∩ _∩ )O 謝謝！??！ 2021 年中央電大期末復習考試小抄大全，電大期末考試必備小抄，電大考試必過小抄 Acetylcholine is a neurotransmitter released from nerve endings (terminals) in both the peripheral and the central nervous systems. It is synthesized within the nerve terminal from choline, taken up from the tissue fluid into the nerve ending by a specialized transport mechanism. The enzyme necessary for this synthesis is formed in the nerve cell body and passes down the axon to its end, carried in the axoplasmic flow, the slow movement of intracellular substance (cytoplasm). Acetylcholine is stored in the nerve terminal, sequestered in small vesicles awaiting release. When a nerve action potential reaches and invades the nerve terminal, a shower of acetylcholine vesicles is released into the junc