Suprachiasmitic Nucleus (SCN) is a small group of cells in the hypothalamus; it lies just above the optic chasm so it can gain input directly from the eyes‚ and therefore the rhythm can be reset by the amount of light entering the eye. The SCN generates its own rhythms‚ probably as a result of protein synthesis (cells in the SCN produce a protein for a period of hours until the level stops further production‚ and then when the protein level drops below the threshold‚ the SCN starts producing the
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Experiment 3: Chemical Equilibrium Purpose The purpose of this experiment was to determine the equilibrium constant for the formation of FeSCN2+. Introduction Chemical equilibrium is the point in a reversible reaction where the concentration of the reactants and that of the products remains constant. This point of equilibrium is referred to as the Kc value‚ which can be obtained using the formula: Kc = [product] [reactant] In this experiment‚ we used a spectrophometer to
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iron (III) thiocyanate (FeSCN2+). This ion is formed in the reaction of iron (III) ion with thiocyanate ion SCN-): Eq.1 Fe3+ (aq) + SCN- (aq) FeSCN2+ (aq‚) The equilibrium constant is the ratio between the reactants and products when the forward and reverse reaction rates are equal. It is calculated from the mass action expression: Eq. 2 Kc = [FeSCN2+] / [Fe3+][SCN-] In order to calculate the equilibrium constant it is necessary to know the concentrations of all ions at
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Fe+3(aq) + SCN-(aq) ↔ FeSCN+2(aq) (Eqn. 3) Equilibrium calculations are simplified by using an ICE (Initial-Change-Equilibrium) table. Since this reaction is run in aqueous solution‚ the K calculated will be Kc (K in terms of concentration)‚ and all concentrations must be expressed in terms of M‚ or moles/liter‚ then reference to the standard state of 1M. To calculate the equilibrium concentrations and K‚ the ICE table is: Fe+3(aq) + SCN-(aq) ↔ FeSCN+2(aq)
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rhythms. When their SCN was transplanted into their ‘normal’ hamsters they exhibited the mutant rhythm. This shows the role the SCN plays in our circadian cycles‚ showing it regulates our sleep patterns and that rhythm entraining is done through the SCN. However‚ this argument can be deeply flawed. The SCN affects other circadian rhythms such as hormone release and these could affect sleep itself as well as individual differences; therefore it may be deterministic to conclude that the SCN is the regulator
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1. OBJECTIVE 1.1 To use Le Chatelier’s principle for determining the effect of change in concentration. 1.2 To use Le Chatelier’s principle for determining the effect of change in temperature. 2. INTRODUCTION Henry-Louis Le Chatelier‚ (born Oct. 8‚ 1850‚ Paris‚ France—died Sept. 17‚ 1936‚ Miribel-les-Échelles)‚ French chemist who is best known for Le Chatelier’s principle‚ which makes it possible to predict the effect a change of conditions (such as temperature‚ pressure‚ or concentration of
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upon emergence on the 179th day‚ in Siffre’s terms it was only his 151st day. From Siffre’s findings‚ we are able to concur that the endogenous pacemakers are still active during isolation‚ but become somewhat distorted over time‚ as the brain’s SCN loses influence from the exogenous zeitgebers and therefore going out of sync by even a minute a day can lead to serious desynchronisation over time. His body temperature circadian rhythm was more stable. It extended slightly to about 25 hours‚ but
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Discuss the role of endogenous pacemakers and exogenous zeitgebers in the circadian rhythm. 24 Markers Circadian rhythm is rhythms that last 24 hours‚ one day. An example of a Circadian Rhythm is the sleep-wake cycle. Because this rhythm occurs daily‚ it is tempting to automatically assume that the factors which control it are exogenous zeitgebers‚ such as natural light patterns‚ TV‚ radio‚ birdsong‚ Research however has gone into this to find out what exactly controls the circadian rhythms.
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rhythm. The main EP is the supreachisatic nucleus‚ which generates circadian rhythms from sensitivity to light. This shows that while both EPs and EZs are important‚ it seems that the SCN is the overriding factor even though it is affected by the EZ of light. Evidence supporting this claim was found in the removal of the SCN in hamster‚ where it was found their circadian rhythm disappeared and failed to return after transplant. While this study is scientifically rigours in terms of controlling variables
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Experiment 11 Date:31-03-2009 Title:Interpretation of reaction by the Le Chatelier’s principle Objective:To determine the factors that affecting the equilibrium position Introduction Iron(III) ions and thiocyanate ions (NCS-) react in solution to produce thiocyanatoiron(III) (FeNCS2+)‚ a complex ion‚ according to the equation : Fe3+(aq) + NCS-(aq) [pic] FeNCS2+(aq) yellow colourless blood red The colour produced by the complex ion indicates the position
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