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.

Discovered in the 1820’s, its pure form from plants, which was a white crystal like substance.

Daphnia;

Daphnia are  , the size varies between 2mm to 3mm. Often used for aquatic

Fresh food.  They have a jump/jerk mode of swimming style. Able to live in swamps, freshwater lakes,

Ponds or rivers.

The average heart rate of a daphnia is 180 in normal conditions. There translucent exo-skeleton means

That they make great subjects of experiments such as the effects of nicotine, adrenaline, caffeine and alcohol.

They have no bones in their body and have a shell around the body except for the head. They can reproduce rapidly & feed on algae and vegetation. Commonly known as the ‘Water Flea’.

Variables;

The variables will be controlled so that the results concluded can remain fair and precise.  

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Water temperature will be controlled to maintain the fairness of the experiment; this means it will be kept at room temperature as best as possible. That will include turning off the microscope so that the illuminator does not heat up the water, this also ties in with the method I will be using which is to count the first 10 seconds of the daphnia’s heart beat then times it by six.

The same microscope will be used so that the distance from the illuminator is the same to keep variables controlled.

The same species of daphnia will be used; different ...

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