Free Will in Experimental Philosophy Essay

Although the â€Å"free will† problem envelops a spectrum of ideas, I agree with the following belief: â€Å"The folk are compatibilists about free will. † While there are, of course, incompatibilists and indeterminists, for the most part, the general population consists of compatibilists. Now, I know experimental philosophy has a problem with the use of generalizations without actual statistics, but throughout this paper, I will explain exactly why the world revolves in a generally compatibilist manner. Firstly, to speak of compatibilism, you’d have to assume that the world is deterministic, meaning that everything that happens from here on out, including human action, is caused by the facts of everything that has happened before it. With that assumption in mind, compatibilist believe that we still have free will as long as we aren’t operating under external limitations. The problem with that is that although compatibilists believe we are free, there is still disagreement on just exactly how free we may be, which is the weak spot indeterminists and incompatibilists use to try to break the argument. One nature of compatibilism is referred to as classic compatibilism. This means that we’d be acting freely as long as we, without being impeded by any outside force, take a course of action that we personally choose for ourselves. These compatibilists believe that it is the presence of impediments such as â€Å"physical restraints, lack of opportunity, duress or coercion, physical or mental impairment, and the like† that would cause us to not act freely (Caruso, 2012). However, this line of reasoning is not accepted by those who support the Consequence Argument. In the simplest terms, this argument states that no one has power over the facts of the past and the laws of nature. Also, no one has power over the fact that the facts of the past and the laws of nature entail every fact of the future (i. e. , determinism is true). Because of that, no one has power over the facts of the future (McKenna, 2004). Compatibilists respond to this by saying that the focal point should be the differentiation between free and un-free, and not by the absence of causes. Other philosophers argue that we act freely when our first order and second order desires become aligned. Because our mental processes are more developed than those of younger children and simpler animals, we have the rationale to decide whether our instincts or raw desires should be acted upon. That rationale is referred to as the second order desires (Frankfurt, 1971). For example, Chris is at the bar with his girlfriend Ana. While Chris has stepped away to the restroom, Jose approaches Ana and flirts with her in a manner that she does not feel comfortable with. Once out of the bathroom, Chris sees this. Enraged, he initially wants to go and physically put Jose in his place. In spite of this, he remembers that he is up for a promotion at work, and getting into a bar fight probably won’t help his chances of receiving it. He tells Ana to collect her things. They leave. What we see here is the protagonist, Chris, experiencing first order desires that make him want to hurt Jose. His second order desires are what tell him that although he is feeling those first order desires, his second order desires are not in agreement and therefore, he shouldn’t act on them. Although some compatibilists seem to be satisfied with this reasoning because it justifies the causation of our actions, it doesn’t explain whether our thoughts and desires are consequences of the past as well. An example would be that Kate feels the desire to take a run in the park and does so. Yet, if determinism is true, which compatibilists believe it is, she is already determined to feel that way, and although she may want to feel that way, without any outside force acting on her she is not free (McKenna, 2004). Her first order and second order desires may even align, but without the ability to do otherwise, due to determinism, she would not be free. Even so, compatibilist Michael Levin says â€Å"minding or accepting one’s desires is as much an effect of past causes as the desires themselves,† but if our internal desires are causally determined, they cannot also be free. All it would be is a different form of causality (Caruso, 2012). Nevertheless, compatibilists argue that it isn’t necessary for an individual to have been able to do otherwise (Nahmias, Stephen, Nadelhoffer, & Turner, 2005). If there were the choices of A through Z and someone that could manipulate me into doing A that would do so if I didn’t do it on my own, I would still have free will if I picked A without the manipulation. In this case, compatibilist see me as having had free will because I chose A on my own. My 1st order desires were aligned with my 2nd and that is why A happened. If I had been manipulated to do so, then the problem of free will would once again come into question, but being that the manipulator is fairly irrelevant to the story since I acted on my own accord, and would have done the same thing without the potential manipulative factor. Also, there a couple of studies done to determine what relationship non-philosophers believed existed between free will, determinism, and moral responsibility. In Study 1, there were three scenarios. Scenario 1 was negative. Scenario 2 was positive, and Scenario 3 was neutral. In all three cases, between 68 – 79% of folk said there was free will. While there were some fluctuations in percentages when it came to the association between free will and the ability to choose otherwise, the amount of participants making judgments that disagreed with incompatibilism was two to three times greater than those that followed along with incompatibilist intuitions. This study was supported by their second study. In this study, they tell the subjects that everything in the universe is caused completely by their genes and environment. The scenario takes twins, Fred and Barney, and places Fred with the Jerksons and Barney with the Kindersons. One day they both find a wallet with $1000. Fred keeps it, while Barney returns it to its rightful owner. When polling the participants, 76% said they both acted on their own free will and could have done otherwise. This shows that the majority of folk believe that compatibilism is true, and while external factors and facts of the past might influence the choice making process, it does not define it; therefore we are free within the confines of a determined universe (Nahmias, Stephen, Nadelhoffer, & Turner, 2005). Now, why do I personally find â€Å"the folk are compatibilist about free will† to be true? Aside from the aforementioned statistics, the reason is that if we did not find a middle ground between free will and determinism, we wouldn’t do any of the things we do. Everything from the grading systems used in schools to receiving a promotion at work all the way to fighting wars is done in a compatibilist manner. The premise of all these concepts is the idea that if you choose do X, having the option of Y, Z will happen. If you work hard enough in school (X), you will receive good grades (Z), even though you can just be lazy (Y). If you are the most productive and pleasant at your job (X), you will receive a promotion (Z). If we go into a war (X), we have the chance of winning (Z). While all the factors in each of those scenarios might have also been determined, there is no reason for us to feel disappointment when we really studied but still managed to only get a B on a test or when we lose troops across seas. Though the previous paragraph does explain that folk believe in free will, it doesn’t explain why folk have the compatibilist view of free will. The reasoning for that is because while compatibilists believe that you can control some aspects of your life, you can’t control all of them. As Michael Levin said, â€Å"Compatibilist usually agree that free will does require behavior at least to be determined, since you cannot freely do what is beyond your control. † For example, we are born and we die. The sun rises. The sun sets. We inhale oxygen and exhale carbon dioxide. There are certain laws of physics that we must adhere to. Some will argue that we believe those to be stable laws of how the universe will operate, but only because that’s what it’s done until now. Tomorrow we might not have the sun rise, and tomorrow we might inhale carbon monoxide and exhale nitrogen. However, since certain things have been fixed for a trustworthy amount of time, we, the folk, have accepted it as determined facts of the universe. The determined factors of the universe are the skeleton upon which we place the flesh that is our free will. ? References Caruso, G. D. (2012). The Folk Psychology of Free Will: Arguement Against Compatibilism. Kriterion – Journal of Philosophy, 26, 56-89. Frankfurt, H. G. (1971, January 14). Freedom of the Will and the Concept of a Person. The Journal of Philosophy, 5-20. McKenna, M. (2004, April 26). Compatibilism. Retrieved from Stanford Encyclopedia of Philosophy: http://plato. stanford. edu/entries/compatibilism/ Nahmias, E. , Stephen, M. , Nadelhoffer, T. , & Turner, J. (2005, October). Surverying Freedom: Folk Intuitions about Free Will and Moral Responsibility. Philosophical Psychology, 18(5), 561 – 584.

advantages Essays - Software, World Wide Web, Computing, Free Essays

advantages Essays - Software, World Wide Web, Computing, Free Essays 2.0 Importance of Facebook now days: According to this research Facebook is a lawful activity in every country of the world, and from a small child to a busy professional business man Facebook is an addiction to all of them. Facebook has become a part of daily routine of people and for some people part of their hourly routine, people of all ages use Facebook for following different purposes. 2.1 Communication: The main purpose of this social network is communication; the main logo of Facebook is "connect and share with the people in your life". Facebook allows its users to chat, talk and share their daily life activities with their friends and family. 2.2 Entertainment Due to the advance features of this network entertainment has become as equal purpose as communication; as a member logs into his Facebook account his attention is readily diverted towards different entertainment stuff like time line applications, online game applications, picture jokes, funny videos and other interesting content. 2.3 Source of Earning Facebook is also used as a source of earning by people i.e. Facebook is one of the most visited websites on internet so it is an excellent website for advertisement and offers about brands and products, therefore Facebook is also used for marketing of business and hence it assists people in earning money. 2.4 Data Storage and Information Some people also use Facebook as data storage i.e. to store their memorable photos and videos on internet as in case their compute data gets corrupt or lost. Facebook is also sometimes used to obtain information about famous people, locations, cultures and events. Facebook also keeps people up to date about the world. 3.0 Usage of Facebook by people of different ages and different regions According to the research carried out Facebook population is made up of Millions of people around the globe. As compared to males, females lead the population on Facebook; young adults aged 18 to 25, possess the most population of the Facebook due to their interests in chatting, entertainment, cyber dating and other youth stuff. After this age sector Facebook is heavily populated from people aged 26 to 34, due to the same interests as of young adults. The rest of the population is covered by people of different ages including children and people over 45. Coming to the regional statics of Facebook usage, Facebook is a lawful activity in every country of the world. America has the most Facebook users of the world, Brazil has the second most users of Facebook in the World and third country with most Facebook users is India. Ireland possesses 59th position in relevance to the Facebook population. All these statistics show that Facebook is huge and on the present day it is the most popular social network and one of the most visited website on internet. 4.0 Advantages and disadvantages of Facebook: Today the world has become a place of instant communication with the help of social networks like Facebook, twitter, Google plus etc. and by other means of communication like emails and telephones. Facebook is the most popular social network on internet and its use is rapidly increasing, according to research carried out Facebook is the most popular communication tool used, followed by SMS and email. "Facebook is the most popular social network in the world, with over 350 million users, so it should come as no surprise to discover that people are using it as a primary tool for communication," said Hazel Butters, CEO of Prompt Communications. As far as communication and sharing Facebook is considered as an excellent tool, but problems arise when Facebook becomes an addiction. Facebook has become a part of daily routine of people and for some people part of their hourly routine and hence they are moving away from their daily healthy activities by spending hours on Facebook. Teens especially are being accused of constantly logged in their account, some specialists narrate that this develops social skills in them which are essential in practical life. But other people believe that this disturbs their studies and their healthy outdoor activities. Privacy is another issue with Facebook, although the social network offers the users full control of their private information

Oil Price and Petrochemical Manufacturing in UAE Essay

Oil Price and Petrochemical Manufacturing in UAE - Essay Example The research investigates the immediate impacts that falling oil prices pose to UAE’s economy. It explores the effects of falling oil prices on UAE’s economy. The relationship between oil production firms and petrochemical producing industries are essential to the research. The research will investigate the impacts and effects of falling oil prices on petrochemical manufacturing in UAE. The falling prices risk the survival of petrochemical manufacturing industries that also contribute to the economic stability and income of UAE. The risked survival may render some of the employees in Petrochemical sector jobless raising the level of unemployment in the country. The unemployment crisis lowers the per capita within the country reducing the country’s Gross Domestic Income (GDP) in turn. Finally, the research will draft and recommend possible solutions to the effects of falling oil prices on UAE’s economy. The International Energy Agency asserts that the fall in oil prices translates into a cut in the production of petrochemical products. The effect of this is a retard in the growth of the petrochemical industries, which are also a major contributor to the UAE’s economy. OPEC reports that a fall in oil prices slows the global growth. A decline in the oil prices increases demand for oil products at the expense of petrochemical products. The source explains the manner in which falling oil prices undermine the competitive advantage of petrochemical products. The reduced competitive advantage lowers the total sales of the products endangering the firms.

The Roman Republic in Sallust's Account, the Conspiracy of Catiline Essay

The Roman Republic in Sallust's Account, the Conspiracy of Catiline - Essay Example Although an account of personal observations and opinions, this document can be considered as a written eyewitness account of an indigenous intellectual of Rome - an onlooker to the establishment, growth and decline of an ancient superpower. By analysing the contents of the document, it is evident that the Roman historian attributed the ascent of the Roman Republic to the valor of the people, that their strength in arms provided them the security of their rights and liberty from various enemies. The Romans’ might and bravery allowed them to forge allies and supporters, thus having provided a firm respect from neighboring city-states and sovereignties. The people upheld valor by bestowing the military culture amongst their young ones. From the childhood up to adulthood, primarily in all generations of Romans, the republic was well protected. Honour and glory became the primary theme of Rome. Sallust furthered the explanation of Roman beginnings by recounting the virtues that ha d transpired after the military conquests and expeditions of its people. Good morals such as loyalty to citizenship, patronage in religion and the natural adherence to justice molded the Roman society. The historian also mentioned in his account that the Romans’ animosity for opponents and their preparedness for battles caused Rome’s neighbours to make ties rather than to make war. With this, the Roman Republic was born. It was built from brute strength and the consolidation of brilliant minds, which produced a formidable state that caused the creation of the Roman law. These laws were protected by the Senate and implemented by the monarchical nature of the republic. Technically, though Sallust’s account can be classified as merely a product of observation and a product of subjectivity, it cannot be denied that the supposed biography intricately described what the Roman society was through the eyes of a true intellectual Roman scholar. His experiences and role i n the writing of the history of Rome makes his account a strong primary source for subsequent scholars of this particular field. Thus, the observation of the author accounts to a very interesting point of view with relation to the climb of the Roman Republic to greatness. Its origins revealed that force and decisiveness were needed to establish an immovable government. Sallust then went to a pessimistic standpoint - the demise and the eventual fall of the Roman Republic. At the time when Rome had military supremacy in Europe, when the Roman army continuously fought battles and repeatedly won, the toils of war caused a spark in the destruction of the values. Looting the wealth of defeated states were the ingredients for the downfall of the great Republic. The need for an expanding Rome almost immediately transformed into a pure desire for the material. The Romans craved for money and treasures, which distorted the Roman theme of honour and glory. Thereafter, Sallust described the con tinuous corruption from an extreme desire for the material to the unjustifiable claim for power, which created tyranny. This attribution of the demise of Rome was simple but revolutionary for the mainstream history of the republic. Sallust had concretely specified the core causes of the destruction of Rome. This is a very humanistic approach to the problems of ancient empires alike. The temptation of grabbing too much power gets the best of its wielder. In this case, Rome which had an obvious record of

What form of audience do social tags of this kind enable Discuss the Essay

What form of audience do social tags of this kind enable Discuss the social and communicative properties of this kind of audience, using these tweets as evidence to support your claims - Essay Example Social tagging also plays a major role in connecting the users who have similar interests. The users can be able to share among themselves relevant piece of information regarding their area of interest (OReilly, & Milstein, 2009). Different tweets are usually posted to address different types of audiences. The different types of audiences have a common characteristic in that they are all imaginary in the mind of the writer. The three main types of audiences to which tweets can be addressed include (Clark 2012); the writer’s audience, the networked audience, and the broadcast audience. The writer’s audience: In this type of audience, the user tries to imagine the potential audience that have a high likelihood of gaining interest in the intended tweet and composes the tweet that is tailored for the perceived audience. The user tries to form a picture of the audience in his/her mind in order to compose a tweet that will meet the needs of that specified group of audience. The user usually expects responses from the audience. The broadcast audience: In type of audience, the user does not have a specific group of audiences in mind. The user just composes a tweet that is intended for any audience. For this situation, the user does not expect to get any response regarding the tweet. They compose a tweet that is meant for the consumption of the general public, and response for them is not a priority. The networked audience: This type of audience combines the characteristics of both the writer and the broadcast audience. Unlike in the broadcast audience, the user here composes a tweet that is intended of a large group of audience, but he/she has an idea of the type of audience to which the tweet is intended for. Just like in the writer’s audience, the user here also expects to get responses from the audience regarding the tweet. According to the sample tweets that have been provided, the form of audience that is most likely to be enable is the

Health promotion initiative Essay Example | Topics and Well Written Essays - 2500 words

Health promotion initiative - Essay Example It should be noted that the area is crime prone and incidences of drug abuse are very common. According to records, a portion of the population shared needles from intravenous drug use and there is widespread homosexual promiscuity. In the 1990s, the Belle Glade community had the highest HIV/AIDS prevalence rate in the United States. The AIDS scourge is widespread in the entire area cutting across all the major demographics of Hispanics and Black Americans. One of the reasons for the high AIDS prevalence rate is the sharing of needles used in intravenous drug injections. The high risk people include drug users who are also engaged in promiscuity. Lack of knowledge and information about AIDS contributes to the high prevalence rates in the region especially among the gay people. These high risk people are not equipped with the right information on AIDS and therefore inadvertently put themselves and the entire community at a high risk of infection. It is therefore important to undertake a health promotion initiative in Belle Glade community so as to curb the issue of HIV/AIDS. Notably, measures have to be put in place to ensure that new infection cases are eliminated and those that are infected get the right information to live in a healthy manner. It is also important to note that the use of drugs and high rates of promiscuity play a major role in the spread of HIV/AIDS in the Belle Glade community. Therefore, the health promotion is intended to cover the whole spectrum of HIV/AIDS spread and infection management. According to the Ottawa Charter (1986), health promotion is based on the social ecological factors that determine the health of the society. Health promotion initiatives aim at mobilizing resources for good health. It should be noted that health promotion is salute-genetic and it involves a multi sectoral approach. Based on the Ottawa

Neurotransmitter and Hormone Receptors

Neurotransmitter and Hormone Receptors 1) Transcription of DNA and translation into protein are tightly regulated in Eukaryota cells. Give an account of the key steps involved. Gene expression is under continuous regulation. This regulation is differentiated between Eukaryotic and Prokaryotic organisms, especially due to matters of complexity. In Prokaryotic organisms the regulation of gene expression is happening only at the stage of transcription and includes one stage. On the other hand, the regulation of gene expression in Eukaryotic organisms is happening not only in transcriptional level, but also at post-transcriptional, translation and post-translation level (Latchman 2007). The figure on the right shows the steps of gene expression that can be regulated. In case where the regulation of gene expression happens in transcriptional level, then the levels of cytoplasmic mRNA and nuclear RNA should be paralleled. On the other hand, in case a gene is being transcribed in the same manner in all tissues, there will be a difference in the majority of tissues between the cytoplasm mRNA and RNA, due to post-transcriptional mechanisms. As a result, in order to distinguish post-transcriptional and transcriptional regulation the first approach is to see if there are changes between the RNA levels in the tissues (Latchman 2007). Initiation of transcription In many cases where there is an increased level of transcription, this results from a high level of transcriptional initiation mediated by RNA polymerase responsible for initiating the process. This means that in a tissue that occurs an active transcription process, the RNA polymerases will be moving beside the gene continuously, and thus increasing the rate of transcript production. In contrast, in tissues where a gene is transcribed at low levels, the initiation of transcription will not be so apparent and the level of transcripts will be significantly low (Latchman 2007). Elongation Except of the initiation of transcription which seems to occur in the majority of the cases, there has been demonstrated that the regulation can also happen during at a post-initiation level by producing a shortened RNA than the full length one. In this case, the transcriptional control seems to happen by blocking the elongation of a newly formed transcript (Latchman 2007). DNA elements The expression of protein-coding genes is regulated also by specific DNA elements, which are located usually upstream of the initiation site of the gene. These DNA elements can influence positively or negatively the transcription of a gene. For example, DNA sequences such as insulators and silencers, suppress the genes transcription (Latchman 2007). Transcription Factors The transcription factors are also important modulatory elements of transcription. The binding of specific transcription factors on the DNA, can either activate or suppress gene transcription (Latchman 2007) . Although so far we discussed the transcriptional control of gene expression, which corresponds to the most abundant transcriptional control mechanism, there have been cases where even though the transcription rate of a gene doesnt change, changes in the synthesis of specific proteins have occurred. This control mechanism occurs between the translational and transcription control and includes splicing of the nascent mRNA, alternative splicing, and regulation of RNA stability. The splicing of the RNA is the process in which the protein coding regions are encoded by exons, after removing the intervening sequences which are named introns (Latchman 2007). The alternative splicing, includes the differentiated processing of RNAs in order to produce different RNA variants (Black 2000). The translational control of gene expression, corresponds to mRNA regulation and is also a very important regulatory stage. In the same manner as transcriptional control, translation can be affected either positively or negatively by altering the levels of specific translation factors, and most of the times it happens at the initiation of the translation process due to differences in the 5 untranslated region of the mRNA. During translation, the 5 un-translated region contains an AUG triplet of bases which is important to be located in a favorable context. This means, that if the ribosome is incapable of recognizing this triplet, then the initiation of translation is inhibited. For example, in a situation which is called leaky scanning, when AUG codons are located upstream, the ribosome has a difficulty to recognize them (Wickens et al. 2000). Furthermore, except of the recognition of the AUG codon, other coding regions seem to play an important regulatory role. For example, some frequencies which are located in the open reading frame of the mRNA (ORF) seem to cause a frameshift at a specific triplet both in viral and mammalian mRNAs (Wickens et al. 2000). Finally, another regulatory element of gene expression includes the post-translational control. This category composes of all the mechanisms that act after translation by modifying the protein levels. Such a mechanism is ubiquitination, which will have as a result the degradation of the ubiquitinated protein in the proteasome (Wang et al. 2013). In conclusion the transcription and translation are highly regulated processes and this take place due to the complexity of Eukaryotic cells, since strict regulation usually corresponds to high complexity. 2) Discuss the role of microtubules and their motor proteins in the motion of cilia and flagella. Microtubules are important elements for various cell movements, such as the chromosomal separation during mitosis and the motion of flagella and cilia. This movement, which happens along microtubules, is highly dependent on proteins that use energy from ATP hydrolysis in order to produce force and movement. These proteins are members of the kinesin and dynein families (Alberts et al. 2002). Cilia and flagella are plasma membrane projections dependent on microtubule formation, and are important for the movement in various eukaryotic organisms. In bacteria, the flagella structures are different from the eukaryotic flagella (Alberts et al. 2002). The movement of these structures has been extensively studied by using animal models, especially sea urchin models which appears to be a very powerful system for flagellar motility. Furthermore, the first scientists to observe this sliding mechanisms driven by dynein across the microtubules, were Summers and Gibbons by using dark-field microscopy (Hirose Amos 2012). In eukaryotic organisms the flagella and cilia are highly similar structures. Firstly, flagella are mostly found in sperm and many hair-like cellular projections with a core composed of microtubules (Cooper 2000). With their rolling motion they permit the cells to swim through liquid media. The cilia, are usually shorter than flagella but their organization tends to be similar. Their beating motion is like the breast stroke of the swimmers, and the cycles of adjacent cilia are quite asynchronous, thus producing the characteristic effect that can be observed through microscope (Alberts et al. 2002). The movement of both each flagellum and cilium is produced by the bending of each ones core, which is specifically termed as axoneme. The axoneme is a structure that is composed of microtubules in conjunction with their associated proteins in a regular and specific pattern. This pattern is composed by nine doublet microtubules which are fused together to surround a pair of microtubules. Th is formation is also known as the 9+2 pattern and is represented in the following picture (Cooper 2000). This type of arrangement is commonly seen in the majority of eukaryotic flagella and cilia forms. The length of these microtubules extends along with the length of the axoneme which can reach the 200 ÃŽÂ ¼m. At specific positions along the distance of microtubules, are located accessory proteins, providing with this a way a cross-bridging between the doublet microtubules. These molecules are dynein proteins, and are located around the perimeter of the axoneme (Cooper 2000). Dynein is a very large molecule (2000 kd), consisting of three heavy chains in conjunction with a variable number of intermediate and light polypeptides that have a weight ranging from 14 to 120 kd (Cooper 2000). The heavy chains are forming a globular domain which binds ATP and is responsible for moving along microtubules. The intermediate chains are responsible for the assembly of the dyneins. The light chains form two distinct groups, in accordance with the molecules that are related with. For example the first group is associated with the heavy chains, while the second group with the intermediate chains. In the cilia and flagella, there is also another specific dynein group, the intraflagellar transport (IFT) dynein, which is important for the association and disassociation of these organelles, and also have transport properties of either membrane proteins or even the IFT themselves (Hirose Amos 2012). The ciliary dyneins, are composed of a different set of arms, the outer dynein arms and a more complex set of inner dynein arms. Each one of this structures plays a different role in the ciliary movement. The outer dynein arms are responsible for the production of the majority of the force required for the ciliary movement, while the inner dyneins, are mostly providing a precise control of this movement (Hirose Amos 2012). Another important feature of the cilia and flagella, is that the minus ends of each microtubule are anchored in a structure which is named basal body. This is highly similar to the centriole, and is necessary for the arrangement of the axoneme microtubules. Each one of the doublets located in the outer part of the flagella or cilia, is formed by the extension of two of the microtubules of the basals body triplets (Cooper 2000). The movement of cilia and flagella is caused by the relative sliding of outer microtubules, driven by the activity of axonemal dynein, and the mechanism is represented in figure 3. The dynein bases attach with the A microtubules while the head of each dynein attaches with the B microtubule. With the green color is represented the nexin link, which binds the microtubules in the axoneme. When the one doublet of microtubules, bends along with the other one, the resulting movement is bending, which is the source of the beating movements of cilia and flagella (Alberts et al. 2002). Scientific evidence suggests that upon ATP hydrolysis the dyneins change their conformational state (Hirose Amos 2012). 3) Describe the most important classes of molecules that participate in common signal transduction pathways In signal transduction pathways, extracellular signals such as hormones or other molecules are registered by membrane receptors and the signal is being transferred inside the cell by a set of reactions. This signal transduction can be mediated by two distinct mechanisms. The first one includes the use of receptors, and other proteins including enzymes. The second one contains a set of molecules which are known as second messengers, that regulate the intracellular signaling (Boon 2009) . The intracellular second messengers, are signal molecules that reach their target by diffusion. They can be divided into two different groups, those with a hydrophobic character (diacyl glycerol or phosphatidyl inositol) and the hydrophilic ones. The hydrophobic messenger are located on the membrane and they can reach the proteins located on the membrane by diffusing through the plasma membrane of the cell. The hydrophilic messengers are located in the cytoplasm and their targets are located in the cytosol as well (Boon 2009). The most important second messengers include the cAMP, cGMP, inositol phosphates, calcium ions, diacylgrlycerol and phosphatidyl inositol phosphates. 3-5 cyclic AMP (cAMP) Is among the most important second messengers and regulates a variety of cellular functions, such as glycolysis, muscle contraction and ion transport. The intracellular concentration of cAMP is regulated by two factors, the adenylyl cyclase and the phopshodiestarases. The former is important for the cAMP synthesis while the latter for its degradation. The activation of adenylyl cyclase is dependent to G-protein coupled receptors and involves the participation of GÃŽÂ ± and GÃŽÂ ²ÃƒÅ½Ã‚ ³ proteins. The degradation of cAMP mediated by cAMP phosphodiesterases, which are being regulated by Ca2+/calmodulin and also by phosphorylation (Boon 2009). In the majority of the cases, the target of the high cAMP concentration is the activation of protein kinases A (PKAs). Initially, in the absence of cAMP the PKA is organized as a tetramer, with two catalytic and two catalytic subunits, and the protein kinase is inactive. When cAMP concentration is increased by adenylyl cyclase, leads to the binding of two molecules to the regulatory subunit and the tetramer dissociation and activation of PKA (Boon 2009). cGMP In the same manner with cAMP, the 3-5-cGMP is extensively spread in the intracellular space. Like in the case of cAMP , the cGMP is formed by guanylyl cyclase from GTP. The cGMP can activate cGMP-dependent protein kinases, after binding to specific locations. In contrast to the PKA kinases, the activation of cGMP-dependent protein kinases is dependent to only one protein chain of these proteins. Specifically, the binding of the cGMP to the regulatory domain of the protein, activates it and permits phosphorylation of other substrates (Boon 2009). Inositol Phosphates The inositol containing phospholipids located in the plasma membrane, are the starting points for the production of many inositol messengers as a response to extracellular or even intracellular signals. The inositol phosphates are important players for the regulation of phospholipase C, which is a very important enzyme in the metabolism of phosphatide inositol. Another important function of these phosphates, is the recruitment of Ca2+ ions that are inside storage organelles, such as mitochondria. The calcium ions are among the most ubiquitous targets of second messengers, and regulate a vast array of actions (Boon 2009). Calcium ions The calcium ions can have a regulatory character in many ways, according to the time, frequency and amount of release rate. This feature, explains the complexity of Ca2+ signals. Still it is not understood how oscillatory calcium signals are regulating various processes. It has been suggested that CaM kinase II participates in the formation of repetitive calcium signals. The high intracellular concentration of calcium is temporary and usually a local phenomenon. The cell contains a variety of transport systems, which can transfer the calcium ions inside the storage locations. These transfer mechanisms are Ca2+ ATPases, which transfer calcium against the concentration gradient. Another mechanism, is the sodium-calcium exchange proteins which are mostly apparent in muscle cells (Boon 2009). Diacylglycerol and phospatidyl inositol phosphates The diacylglycerol is being produced by the metabolism of the membrane phosphatidyl inositol phosphate, after the effect of two distinct enzymes, the PLCÃŽÂ ³ and PLCÃŽÂ ². The diacylglycerol (DAG) is then responsible for activating the protein kinase C, which plays an important role in cell proliferation through phosphorylation of various substrate proteins (Boon 2009). Except of DAG, the metabolism of phosphatidyl inositol diphosphate, produces the inositol triphosphate, which increases intracellular calcium levels by binding to specific receptors (Boon 2009). Conclusively, signal transduction is a highly regulated mechanism, which permits the transmission of an extracellular signal inside the cell, and a subsequent cellular response. Among the most important molecules that are participating in this process, we distinguished some members of the family of the second messengers, such as calcium ions, diacyl glycerol and phosphatidyl inositol. 4) Describe the steps of neurotransmission. The process of neurotransmission can be divided into five distinct steps. The first includes the synthesis of the neurotransmitter, the second the storage of the neurotransmitter into transport vesicles, the third the influx of calcium and exocytosis of neurotransmitter, the fourth the binding of the neurotransmitter at the postsynaptic membrane and the fifth the deactivation of the neurotransmitter. The low weight neurotransmitters are synthesized in the cytoplasm of the cell, where enzymes act and convert them into mature neurotransmitters. These enzymes are produced in the neuronal cell body and are transferred to the presynaptic terminal via the slow axonal transfer system. When the new transmitters are synthesized in the cytoplasm, certain mechanisms need to follow for transporting them to the synaptic membrane. On the other hand, the neuropeptides which is the other category of known neurotransmitters, are produced in the neuronal cell body, and need to be transferred a long distance in order to reach the site of secretion. For this reason, they are transported from the soma of the neuron to the presynaptic terminal with the fast axonal transport (Hyman et al. 2009). The small-molecule neurotransmitters, such as acetylcholine and amino acids, are stored into vesicles of 40-60 nm diameter. The primary characteristic of these vesicles, is that in electron micrographs they appear with a clear center area. The storage, requires specific proteins which are located in the membrane of the synaptic vesicles in the presynaptic neuron, the vesicle monoamine membrane transporters (VMAT). In contrast to the small-molecule neurotransmitters, the neuropeptides, are stored into synaptic vesicles with a larger size (90 to 250 nm). In electron micrographs, they seem to have a center relatively more dense than the synaptic vesicles of the small neurotransmitters (Purves et al. 2001). After the influx of calcium into the pre-synaptic cytoplasm, it begins the process of neurotransmitter release. The first step of this exocytosis, includes the docking of the synaptic vesicle membrane at the active zones plasma membrane. The second step is priming. This corresponds to an ATP dependent maturation of the synaptic vesicles that are being docked in the membrane of the active zone but cant be induced by Ca2+. The result of this maturation, is that the primed vesicles can immediately release their content after a Ca2+ influx. The third step of this process includes the fusion of the synaptic vesicle with the presynaptic membrane, which allows the exocytosis to happen. In this step, the function of the protein synaptotagmin is of high importance, since it senses the levels of Ca2+ and regulates with this way the fusion of the vesicles. The final step of this step includes the quantal release of the neurotransmitter with a mechanism of exocytosis. The exocytosis is synchroni zed with the influx of Ca2+ and its induction is controlled by the depolarization of the nerve terminal. After the release of neurotransmitter at the synaptic cleft, the membrane of the vesicle will be recycled with a process of endocytosis (Hyman et al. 2009). After the exocytosis, the neurotransmitter starts to diffuse across the synaptic cleft and targets the post-synaptic neuron and its receptors which are localized on the membrane. The binding of the neurotransmitter to the postsynaptic membrane, will cause both biochemical and electrical alterations. Specifically, an excitatory signal will depolarize the membrane and thus a positive charge will pass inside the cell. This depolarization is caused by the opening of sodium channels located on the post-synaptic membrane, which permits the influx of sodium ions across the membrane. On the other hand, an inhibitory signal will hyperpolarize the cell, and thus a positive charge will flow with a direction outside of the cell. This hyperpolarization is induced by an inhibitory postsynaptic potential (IPSP) which cause the influx of chloride ions, which make the membrane potential more negative and the propagation of the action potential significantly more difficult (Hyman et al. 2009). When a neurotransmitter finishes its function, the next step is to be removed from the synaptic cleft. When the local neurotransmitter concentration falls, the neurotransmitter unbounds from the post-synaptic receptor. After this, the neurotransmitter can be either degraded by specific enzymes, or reuptaken by high affinity receptors. The latter corresponds to the most common way of neurotransmitter removal, and includes the reincorporation of the neurotransmitter into the pre-synaptic terminal by endocytosis. This permits the neurotransmitter to be recycled inside the cell. The remaining percentage of neurotransmitters, follows the other path of removal which corresponds to the enzymatic degradation. A characteristic enzyme is acetylcholinesterase (AChE) which degrades the neutrotransmitter acetylcholine into acetate and choline. Another examples of such enzymes include catechol-o-methyltransferase (COMT) and monoamine oxidase (MAO) (Naik 2015). 5) Describe with examples the major mechanisms of action of the different types of neurotransmitter and hormone receptors. In 1907, the physiologist Langley, introduced the aspect of receptor molecules, in order to explain specific properties of molecules on muscle and nerve cells. The neurotransmitter receptors are proteins located in the post-synaptic plasma membrane and contain an extracellular site, specific for the binding of a neurotransmitter. The neurotransmitters, have two distinct families of receptors. The first one, the ligand-gated ion channels or ionotropic receptors, combine the properties of ion channels by having also a neurotransmitter binding domain on their outer part of the membrane. The other family of receptors, are the metabotropic receptors, because the movement of ions depends on certain metabolic steps. The important difference of these channels with the ionotropic channels, is that they dont have an ion channel in their structure, in contrast they have a domain which affects the channels through activation of G proteins, and these receptors G protein coupled receptors (Purves et al. 2001). G protein coupled receptors (GPCRs) are the largest family of membrane protein signaling molecules. The activation of these proteins can be achieved by various ligands, thus modulating the activity of a diverse set of signaling pathways (Kobilka 2007). Nowadays, it is estimated that the human organism contains approximately 800 unique GPCRs, and the 460 of them are assumed to be olfactory receptors (Fredriksson et al. 2003). Their main characteristic is that they contain seven transmembrane-spanning segments, which coordinate the position of the proteins N-terminus at the extracellular space and C-terminus at the intracellular space. Studies in neuromuscular synapse, have demonstrated in detail the neurotransmission mechanism. The binding of the acetylcholine to the postsynaptic receptors, leads to the opening of ion channels. Specifically, the binding of two Ach to a receptor, causes an influx of sodium for milliseconds. In real situations, when an action potential reaches a presynaptic neuron, millions of ACh molecules are secreted into the synaptic cleft. As a result, a high number of AChs will bind to numerous receptors, located on the postsynaptic membrane. The opening of these channels will cause the membrane to depolarize, and the opening of voltage-gated sodium and potassium channels (Purves et al. 2001). When the postsynaptic membrane potential becomes more negative even from the resting potential, the end plate current increases, and decreases when the membrane potential is more positive. At very positive potential, there is a reverse polarity which cause the current to convert form an inward to an outward one (Purves et al. 2001). The other category that we will discuss, the hormones, are produced most of the times by specific cells, and initiate a reaction in certain cell types. Only the cells that have hormone receptors, can be used as hormone target cells. These receptors, recognize certain hormones according to their chemical structure. The classes of these receptors are two, the membrane bound receptors, which are transmembrane proteins and the second category the intracellularly localized receptors which are intracellular receptors (Boon 2009). The membrane bound receptors have an extracellular domain which is linked with an intracellular one. The binding of a hormone are following the rules of noncovalent interactions. In general, signaling molecules for example adrenaline, binds to their receptors with a very high affinity, even higher than the one observed between an enzyme and a substrate. After the binding and the recognition of adrenaline by the receptor, this signal is converted into an intracellular signal, which targets the nuclear compartment. According to the type of the receptors which will bind, adrenaline can cause inhibition of insulin secretion, glycogenolysis and glycolysis (Boon 2009). Furthermore, the hormone insulin, uses for signal transduction a set of tyrosine kinases receptors. The receptors that have tyrosine kinase (TK) activity (RTKs), contain a specific domain for binding ligand molecules located on the extracellular side. Inside the lipid bilayer there is a single alpha-helical element, and inside the cytosol another part that harbors a TK domain. When the RTKs are not bound with the ligand molecule, most of them are in their monomeric state. The only exception of this paradigm is the insulin receptor and in general its family members. When extracellular stimulus is absent, in our case insulin, the kinase domain of the receptors remains in its inactive, auto inhibited state. In this phase, the receptors either have very low kinase activity, or they havent at all. After the binding of insulin on the receptor, the consequent transformational changes that lead to the activation of the TK domain. The activation process of TK includes a trans-autosphorylation of tyrosine residues at segments inside and outside of the TK domain. 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