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How Caffiene Affects Heart Rate

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Does Caffeine Affect a Daphnia's Heart Rate? Hypothesis; My hypothesis is that a daphnia's heart will beat faster when it receives a dose of caffeine. Introduction; Using a human subject could conclude unreliable results if they have a high tolerance to caffeine or have some amounts of caffeine already in them, Daphnia have translucent bodies and under a microphone they're heart can be seen beating, this makes them excellent subjects to carried out the experiment on. Caffeine & Effects; This is because caffeine is a class of methylxanthines which block receptors on the surface of the heart. Because caffeine blocks the adenosine (Believed to promote drowsiness which increases the longer the organism is awake) in the heart and causes the heart to beat faster. Due to the structure of caffeine it binds to the same receptors as adenosine does. Caffeine also inhibits enzymes such as cyclic nucleotide phosphodiesterases which reduces the stimulatory signals released when excitatory neurotransmitters activate neurons in the Central Nervous System (CNS), because they are inhibited by the caffeine the stimulatory signals last for longer which gives the alertness effect in the CNS and can also increase heart rate and blood pressure. ...read more.


Care when handling chemicals as they may stain. Dispose of Daphnia properly The Daphnia being used are for the good-will of science and to gain knowledge, they are used sparingly and if possible will be return to the sample. However there is a possibility that the daphnia can decease and this will be taken into account. Method; The control of the experiment is a pure distilled water solution without caffeine that will be used to determine a base for my experiment. The other solutions will be caffeine that is 100% Distilled water will be called S00, 30% diluted, 20% diluted, 10% diluted. Below is a chart that has the measurements of each solution that will be used in the test. Test; Caffeine; Water; Mean; Standard Deviation; S00 ------- ------ 192.2 25.76 S30 6cm-3 18cm-3 256.2 28.27 S20 6cm-3 12cm-3 301.2 13.97 S10 6cm-3 6cm-3 342.4 19.61 A Daphnia will be extracted and placed onto a cavity slide per trial, caffeine will be added to the slide, its heart beat will be counted for 10 seconds then multiplied by 6, this will be carried out 5 times per solution and each trial will start with a daphnia that has not been affected by the caffeine already. ...read more.


The parasite kills from host-to-host, however the parasite has evolved to only kill the host when it has finished producing spores. (2) (3) A limitation in the experiment was that only the BPM could be recorded and that the time In which it takes the caffeine to effect the daphnia throughout, at its peak and after the Trials have been concluded. One modification to the experiment could be that different diluted solutions could be tested e.g. 00,50,100 so that the results can be compared and to test if there is a pattern or equation that can be made from it between the distance in solution and amount of heart beats. I would not change the amount of trials carried out per solution, I think they provided stable and precise data for conclusions to be made from. Conclusion; Based on the results, they show that caffeine does affect daphnia due to the chemical processes in the body which occur in humans as well. The results prove the hypothesis correct, and the data is accurate, precise and reliable, we can see this with the trend lines and the standard deviation not being over a large area. The graph will all of the results binded into them show a positive increase in the amount of heart beats and the experiment results were recorded without bias to the hypothesis and the outcome which was unknown at the time. ...read more.

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