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n. a catecholamine neurotransmitter and adrenal hormone that is the end product of the metabolism of the dietary amino acid tyrosine. It is synthesized primarily in the adrenal medulla by methylation of norepinephrine, which itself is formed from dopamine by the action of the enzyme dopamine β-hydroxylase. As a hormone, it is secreted in large amounts when an individual is stimulated by fear, anxiety, or a similar stress-related reaction. As a neurotransmitter, it is the primary stimulant of both alpha-adrenergic receptors and beta-adrenergic receptors. Thus, it increases the heart rate and force of heart contractions, relaxes bronchial and intestinal smooth muscle, and produces varying effects on blood pressure as it acts both as a vasodilator and vasoconstrictor. Also called adrenaline.

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Psychology term of the day

February 26th 2024




1. an error in reasoning or argument that leads to a conclusion that may appear valid but is actually invalid. A fallacy may be formal or informal. A formal fallacy involves a violation of a principle of formal logic. An informal fallacy leads to an invalid conclusion because it is misleading in its language or appears to apply to a situation when it does not really apply. See also either–or fallacy; false analogy; false authority; false cause; historical fallacy.

2. more generally, any mistaken idea. —fallacious adj.