Neuromodulation and Neural Plasticity :: Biology Essays Research Papers

Neuromodulation and Neural Plasticity Neuromodulatory synaptic transmission differs from classical chemical synaptic transmission in both mechanism and function. The function of a classical synapse is to convey information rapidly from the presynaptic neuron to its target cell, producing a short-term effect. The neuromodulatory synapse may do the same initially, but its primary function is to transmit information that will have long-lasting effects on the postsynaptic neuron's metabolic activity, and on its response to subsequent input. These effects are fundamental to the development and adaptation of the nervous system, and are believed to be the basis of such higher functions as learning and memory. Neurotransmitters released from a classical presynaptic neuron bind to specific receptor proteins in the postsynaptic cell membrane, causing ion channels in the membrane to open or close. If the resulting flow of ions depolarizes the membrane relative to its resting potential, the probability that an action potential will be generated increases, and the synapse is considered excitatory. If the ion flow results in a net hyperpolarization of the membrane, the probability that an action potential will be generated decreases, and the synapse is considered inhibitory. Neuromodulatory synapses can be either excitatory or inhibitory. A neurotransmitter released from the presynaptic neuron may cause the postsynaptic membrane to depolarize or to hyperpolarize by the same mechanism used in classical synapses, but the resulting postsynaptic potential will be relatively weak and slow. Whereas a neurotransmitter in a classical synapse may induce postsynaptic effects lasting from ten to one hundre d milliseconds, a neuromodulator's postsynaptic effects may persist from several hundred milliseconds to several hours. Neuromodulation of the postsynaptic neuron depends not so much on the neurotransmitter as on the receptor to which it binds, called a metabotropic receptor. Whereas classical ionotropic receptors affect postsynaptic membrane permeability directly, metabotropic receptors effect changes in the postsynaptic neuron via intracellular molecules called a second messengers. When a neurotransmitter binds to a metabotropic receptor, a protein inside the postsynaptic cell initiates a cascade of biochemical events that influence the neuron's future response to stimuli. Although the neurotransmitter, or "first messenger," becomes inactivated rapidly, the effects of the second messenger may last several days. One way in which the second messenger induces prolonged effects is by initiating the synthesis of new proteins, which remain in the cytoplasm of the postsynaptic neuron, influencing its activity. Certain proteins can affect the genome of a postsynaptic cell, permanently altering the cell's ac tivities.

Effect of Art Essay

Traditionally, we have believed that art imitates life. The painter represents what he or she sees by producing a scene on a canvas. The sculptor does the same with bronze or stone. A photographer or film maker does it even more directly. A writer describes life in his or her books. This simple concept is known as mimesis. But some have questioned the one-way nature of mimesis by arguing that art also changes the way we view the world, and in fact, life sometimes imitates art rather than the other way around. The person who first articulated this belief effectively was Oscar Wilde. Speaking about the foggy conditions in London in the late 19th century, he wrote that the way we perceive them changed because of art. Referring to the â€Å"wonderful brown fogs that come creeping down our streets, blurring the gas lamps and turning houses into shadows† he argued that â€Å"poets and painters have taught [people] the loveliness of such effects†. According to Wilde, â€Å"They did not exist till Art had invented them.† And you don’t have to look too far to see anti-mimesis in our lives. To what extent is our outlook on life altered by ideas we read in books? The portrayal of people in films? The styles we see in fashion photography? One great example of this is the TV series The Sopranos, and how it affected both the Mafia in the USA and the FBI. Art’s influence on society: propaganda and censorship Throughout history, it has always been the case that art has the power to change society, especially when new media are used to express an idea. During the First World War, for example, movie cameras were used for the first time to record trench warfare – when the film was shown in cinemas in Britain, audiences ran out screaming. This led to the government censoring further such use of such a powerful medium. And in government censorship, and use of art as propaganda, we see how seriously governments take the effect of art. All of the major dictators of the C20th understood the power of art to influence the population. In Nazi Germany, Hitler set up the Ministry of Propaganda and National Enlightenment. It was headed by Goebbels, who made sure that nothing was published, performed, or exhibited without his approval. When this happens, you know there isn’t going to be a happy ending. And what Goebbels approved, of course, only fit in with Nazi ideology and ideas. In terms of art, this meant no modern and abstract art, certainly nothing hostile to the regime, and nothing that featured images other than the stereotypical blonde-haired, blue eyed set in idyllic pastoral scenes of blissful happiness. In Stalinist Russia, there was also a keen understanding of the power of art. Art portrayed contented peasants, industrious workers, and Stalin himself. In fact, Stalin was shown god-like in many paintings, a phenomenon known as the Cult of Stalin. Just as in Germany, gigantic architectural projects expressed the power of the state. However, there is no doubt that in Russia there were greater artistic achievements than in Nazi Germany. Composers worked with fewer hindrances – as seen in the works by Prokoviev and Shostakovich, and film-makers such as Eisenstein emerged. Art’s influence on society: the trial of Lady Chatterley’s Lover But even under less oppressive governments, the artistic expression of certain ideas can be subject to control. One great example is the book ‘Lady Chatterley’s Lover’ by DH Lawrence, which was deemed offensive on many levels. In this book, Constance Reid, a woman from a progressive liberal middle class family marries a minor member of the aristocracy, Lord Clifford Chatterley, and takes the title ‘Lady Chatterley’. But her husband is injured in the First World War, confined to a wheelchair, and left impotent. Despite this, he becomes a successful writer and businessman. It is more his obsession with financial success and fame rather than any physical difficulties which come between him and his wife, and she begins an affair with their gamekeeper, Oliver Mellors. The largely aristocratic ‘establishment’ of Britain at the time – the book was published in Italy in 1928 – were shocked by many aspects of the book. First, there was the fact that the book was ‘obscene’, in the way it went into explicit detail the affair that took place (see below). Second, there was the fact that a women was breaking her marriage vows, something considered far worse than a man behaving in the same way. Finally, it represented an intimate relationship between a member of the ‘lower’ classes (although it emerges during the story that Mellors is actually well-educated, and became an officer in the army during the First World War) and the ‘upper’ classes, a concept that was totally taboo in Britain at that time. The book was duly banned. But the book was republished by Penguin books in 1960. The attorney general, Reginald Manningham-Buller (dubbed ‘Bullying-Manners’ by the journalist and author Bernard Levin) had to read only four chapters to decide to prosecute Penguin books for publishing it. What annoyed him was not just the content, but the fact that the price of the book meant it was affordable to women and members of the lower classes (remember that only few women worked at this time, and husbands were generally in charge of family finances). The trial was a disaster for Manningham-Buller and the prosecution. They had failed to find any experts to support their case, in stark contrast to Penguin’s defence team, which had brought in authors, journalists, academics, and even members of the clergy to defend the book. Manningham-Buller and his team had very little idea of what Lawrence had been trying to express in his book, regularly being caught out by the superior insight of the witnesses they were trying to catch out. And although they tried to shock the jury – in his opening speech, Manningham-Buller announced: â€Å"The word ‘fuck’ or ‘fucking’ appears no less than 30 times . . . ‘Cunt’ 14 times; ‘balls’ 13 times; ‘shit’ and ‘arse’ six times apiece; ‘cock’ four times; ‘piss’ three times, and so on.† – they were unable to prove that the book would have a negative influence on the readers it was aimed at. According to the Guardian: No other jury verdict in British history has had such a deep social impact. Over the next three months Penguin sold 3m copies of the book – an example of what many years later was described as â€Å"the Spycatcher effect†, by which the attempt to suppress a book through unsuccessful litigation serves only to promote huge sales. The jury – that iconic representative of democratic society – had given its imprimatur to ending the taboo on sexual discussion in art and entertainment. Within a few years the stifling censorship of the theatre by the lord chamberlain had been abolished, and a gritty realism emerged in British cinema and drama. (Saturday Night and Sunday Morning came out at the same time as the unexpurgated Lady Chatterley, and very soon Peter Finch was commenting on Glenda Jackson’s â€Å"tired old tits† in Sunday Bloody Sunday and Ken Tynan said the first â€Å"fuck† on the BBC.) Homosexuality was decriminalised, abortions were available on reasonable demand, and in order to obtain a divorce it was unnecessary to prove that a spouse had committed the â€Å"matrimonial crime† of adultery. Judges no longer put on black caps to sentence prisoners to hang by the neck until dead. Can we say, though, that it was art in this case that changed society, or was it an interaction between human sciences (ie, the law) and the arts (the book) that led to change? This is from the same Guardian article: †¦the message of Lady Chatterley’s Lover, half a century after the trial, is that literature in itself does no harm at all. The damage that gets attributed to books – and to plays and movies and cartoons – is caused by the actions of people who try to suppress them.

Did Politics Fuel the Space Race

A transcript of a meeting at the White House reveals that politics, more than science, may have fueled Americas race to the moon against the Soviets. The transcript, released by the National Aeronautics and Space Administration (NASA), records a meeting between President John F. Kennedy, NASA Administrator James Webb, Vice President Lyndon Johnson and others in the Cabinet Room of the White House on November 21, 1962. The discussion reveals a president who felt landing men on the moon should be NASAs top priority and a NASA chief who did not. When asked by Predsident Kennedy if he considered the moon landing to be NASAs top priority, Webb responded, No sir, I do not. I think it is one of the top priority programs. Kennedy then urges Webb to adjust his priorities because, This is important for political reasons, international political reasons. This is, whether we like it or not, an intensive race. NASA Fears Dangers of Moon Mission The worlds of politics and science were suddenly at odds. Webb told Kennedy that NASA scientists still had grave doubts about the survivability of a moon landing. We dont know anything about the surface of the moon, he states, going on to suggest that only through a careful, comprehensive and scientific approach to manned exploration could the U.S. gain pre-eminence in space. In 1962, NASA was still generally perceived as a military operation and all of the astronauts were active duty military personnel. To Commander in Chief Kennedy, himself a decorated World War II hero, the survivability of military missions undertaken by military personnel, was rarely the main go-no-go factor. Stressing the importance of beating the Soviets to the moon, Kennedy tells Webb, We hope to beat them to demonstrate that, starting behind, as we did by a couple of years, by God we passed them. Hello,  Comrades! Sputnik Calling   In the couple of years the U.S. had fallen behind, the Soviets had launched both the first earth-orbiting satellite, Sputnik in 1957, and the first earth-orbiting human, Yuri A. Gagarin. Also in 1959, the Soviets claimed to have reached the moon with an unmanned probe called Luna 2. This largely unanswered string of Soviet space successes had already left Americans with chilling visions of nuclear bombs raining down on them from orbit, maybe even the moon. Then, just a few weeks before the Nov. 1962 Kennedy-Webb meeting, a national near-death experience—the Cuban Missile Crisis—solidified beating the Soviets to the moon as an absolute necessity in the hearts and minds of the American people. In his 1985 book, The Heavens and the Earth: A Political History of the Space Age, Pulitzer Prize-winning historian Walter A. McDougall provides a behind-the-scenes view of space race politics that took place between U.S.  President Kennedy and flamboyant Soviet Premier Nikita Khrushchev. In 1963, just two years after asking Congress to help â€Å"put a man on the moon by the end of the decade,† Kennedy, in a speech before the United Nations, tempted domestic criticism by asking America’s then Cold War archenemy Russia to come along for the ride. â€Å"Let us do big things together . . .,† he said. After a month of silence, Khrushchev joked of Kennedy’s invitation, stating, â€Å"He who cannot bear earth any longer may fly to the moon. But we are all right on earth.† Khrushchev later went on to throw up a smoke screen by telling reporters that the U.S.S.R. had withdrawn from the moon race. While some foreign policy analysts feared this might mean the Soviets intended to use the money for their space program to develop orbiting platforms for launching nuclear weapons rather than for manned missions, no one knew for sure. Of the Soviet Union and its space race political stance, McDougall concluded that â€Å"no previous government in history was so openly and energetically in favor of science, but neither had any modern government been so ideologically opposed to the free exchange of ideas, a presumed prerequisite of scientific progress.†Ã‚   Money Enters the Equation   As the White House conversation continues, Kennedy reminds Webb of the fantastic amounts of money the federal government had spent on NASA and asserts that future funding should be directed exclusively toward the moon landing. Otherwise, declares Kennedy, we shouldnt be spending this kind of money because Im not that interested in space. Speaking at the official release of the tape, Kennedy Library Archivist Maura Porter suggested that the Kennedy-Webb discussion shows the Cuban Missile Crisis may have caused President Kennedy to view the space race as more of a Cold War battlefield than a field of scientific advancement. The Cold War Speeds the Space Racers As nuclear tensions lessened, Kennedy eventually sided with Webb in pushing NASA to achieve broad scientific goals, according to John Logsdon, director of the Space Policy Institute at George Washington University. Kennedy even proposed a joint U.S.-Soviet moon landing mission in a September 1963 address to the United Nations. Moon Rocks Come to America Six years after the White House meeting between Kennedy and Webb, on July 20, 1969, American Neil Armstrong, on board Apollo 11, became the first human to set foot on the moon. The Soviets had by then largely abandoned their lunar program, working instead on extended manned earth-orbital flights culminating years later in the long-lived Mir Space Station. Historic Tidbit of Trivia: APOLLO was an acronym used by NASA for Americas Program for Orbital and Lunar Landing Operations. Between 1969 and 1972, a total of twelve Americans walked and drove the surface of the moon on six separate missions. The sixth and final Apollo lunar landing came on Dec. 11, 1972, when Apollo 17 delivered astronauts Eugene A. Cernan and Harrison H. Schmitt to the moon. Earthlings have not visited the moon since.