An experiment to see if caffeine affects heart rate

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An experiment to see if caffeine affects heart rate

Hypothesis

To test if caffeine affects the heart of daphnia

Prediction

I think that the higher the concentration of the caffeine solution the faster the heart rate will be. Caffeine is also known as trimerhylaxanthine and the chemical formula is C8H10N4O2. The caffeine will be absorbed into the blood where it travels into the brain. The caffeine molecule is the same size as the adenosine. Adenosine is a chemical in the blood that attaches to the nerve cells and slows it down therefore making a person tired. As caffeine is the same shape as adenosine the caffeine molecules attach to the nerve cell instead meaning, the adenosine molecule cannot get into the nerve cell. As the caffeine is a stimulant it then stimulates the nerve cell and this makes a person feel more awake and speeding up the heart rate.

        Caffeine also stimulates the pituitary gland to release cortiocostreiods, which then travel to the adrenal gland triggering the release of adrenaline. Adrenaline is a hormone, which helps to stimulate the body therefore making the heart beat faster.

Variables

The independent variable is the variable that we change. In this experiment the thing we are measuring in the concentration of caffeine that the daphnia is put into.

        The dependent variable is the variable in the experiment that we measure. In this experiment it is the heart rate of the daphnia.

        The extraneous variables which could affect the results of the experiment include; stress, temperature of room , heart problems, how long the daphnia has been kept out of the pond culture. The extraneous variables can be controlled by being careful when taking the daphnia out of the water to long as this can bring on stress. We can control the temperature of the room by carrying out the experiment on the same day and in the same place to ensure there are no temperature changes.

Fair test

Each daphnia tested first undergoes a control, this means that the daphnia’s heart rate is tested in it’s natural environment. This ensures that an accurate result can be obtained as a comparison between the natural heart rate and the heart rate when affected by caffeine can be made.

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        This experiment is a blind experiment meaning that the person who is recording the heart rate does not know the concentration of the caffeine being used. This ensures that the experimenter pays exactly the same amount of attention to each experiment ruling out personal bias. Sometimes, if an experimenter knows that there is a low concentration of caffeine being used they may pay less attention as they are expecting the heart rate to be less. This may give an inaccurate result.

        The person recording the heart rate is kept the same to ensure there is no human error. For ...

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