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Does Caffeine Affect Heart Rate?

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Mos DOES CAFFEINE AFFECT HEART RATE? AIM: To investigate the effect of caffeine on the heart rate of Daphnia (water fleas). Caffeine is a stimulant drug, which causes increased amounts of stimulatory neurotransmitters to be released. APPARATUS: Culture of Daphnia Cavity slides and cover slips Dropping pipettes Distilled water Cotton wool Caffeine solution Stop clock Paper towel/ filter paper Microscope Lamp PREDICTION: I believe that an increase in caffeine concentration in the surrounding water on the daphnia results in an increase in heart rate. This is known because caffeine is a stimulant, which has the effect, among other things, of increasing the heart rate of any living organism, which consumes or absorbs it. Caffeine causes increased amounts of stimulatory neurotransmitters to be released. At high levels of consumption, caffeine has been linked to raised blood pressure and raised heart rate. A high dosage of caffeine results in an increased neurone firing in the brain. The pituitary glad sees all the activity and thinks some sort of emergency must be occurring, therefore releasing hormones that tell the adrenal glands to produce adrenaline. ...read more.


to obtain the BPM. This experiment, using the distilled water solution, was repeated a further 2 times with other Daphnia, and fresh slides and cover slips, using the same procedures as above. The experiment, using the caffeine solution was then carried out 3 times, again, using the same procedures. In each of the 3 experiments, however, different concentrations of caffeine solution were used. In the first, 2 drops were used, in the second, 4 drops were used, and in the third and final, 6 drops were used. An average for the results was then worked out by adding the results and dividing by 3. RESULTS: SOLUTION HEART BEAT/15 SEC BPM AVERAGE BPM 1 2 3 1 2 3 Water 16 19 21 64 76 84 74.67 Caffeine 86 93 99 344 372 396 370.67 CONCLUSION: The results obtained clearly show that the higher the concentration of the caffeine, higher the heart rate, as seen on the bar graph. This proves the original prediction. As was mentioned before, the reason for this is most likely be due to the fact that caffeine is a stimulant and an increase in its concentration results in a higher heart rate. ...read more.


A daphnia's heart rate can rise to a very high rate, especially when using a stimulant such as caffeine, and thus it can be very difficult to measure using a ticker timer or even dotting on a paper. This is due to the restraints of the human reflexes � they are simply not fast enough in some cases. Another major factor is that it is feasible that a larger daphnia would not be as greatly affected by a certain concentration of caffeine as a smaller daphnia. This is because a larger daphnia would have a more diluted level of caffeine within its system. Other factors, which could affect the heart rate are, the temperature of water surrounding daphnia, the concentration of chemicals in the surrounding water (could reduce caffeine intake), amount of water surrounding daphnia, the concentration of oxygen in the surrounding water, the drops of iced water into the slide (could affect the temperature). The concentration of other gases in the surrounding water such as carbon dioxide could also affect the temperature as it can limit the amount of oxygen in the surroundings. The caffeine solution used could not have been fully mixed in with the water, therefore the concentration taken could not have been what it was actually planned to be. ...read more.

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