When the human body receives a neurotransmitter from outside of the body. The first aspect to consider is if the neurotransmitter entered through the blood vessels by injection or by oral intake. When the neurotransmitter is in the blood stream can reach the receptor of this neurotransmitter in the body. If the person is healthy, the receptor will receive an overstimulation so the answer will be stronger than normal quantities of the neurotransmitter. Nevertheless, the reuptake of the neurotransmitter will occur in the same way as natural neurotransmitter.
Answer: d. Confounding
Explanation:
In the context of a scientific study such as this one, a confounding factor is one that has influence on both the exposure and event variable(s), which may lead to over- or underestimation of the direct relationship between them (if any).
For instance: In this example, researchers may have had reason to believe that male gender is associated with both higher risk of obesity (the exposure variable) and adult-onset asthma (the event variable). If gender is not taken into account, one may claim that the finding of an association between obesity and asthma is simply an artifact due to the high proportion of male patients (likely to present with both). <em>Controlling</em> for that variable (such as by matching, as in this example) allows researchers to test for this hypothesis.
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