Glossary O

opioid use disorder refers to cognitive, biological, behavioral, and social problems associated with the use and abuse of opiates and their synthetic variants.

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Opioids are substances that include morphine and heroin, producing euphoria followed by a tranquil state; in severe intoxication, can lead to unconsciousness, coma, and seizures; can cause withdrawal symptoms of emotional distress, severe nausea, sweating, diarrhea, and fever

Opium refers to the dried sap produced by the poppy plant

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Opium poppy is a plant cultivated for centuries, primarily in Eurasia, for Opium, a narcotic that acts as a central nervous system depressant

OPO refers to an organ procurement organization; one of the authorized local or regional agencies that implements procedures to offer the opportunity of organ donation and to recover donated organs

Opponent neurons is a neuron that has an excitatory response to wavelengths in one part of the spectrum and an inhibitory response to wavelengths in the other part of the spectrum.

Opponent-process theory refers to a theory which states that strong emotions tend to be followed by an opposite emotional state; also the strength of both emotional states changes over time.

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Opponent-process theory of color vision refers to a theory originally proposed by Hering, which claimed that human perception of color is determined by the activity of two ("9 opponent mechanisms: a blue–yellow mechanism and a red–green mechanism. The responses to the two (2) colors in each mechanism oppose each other, one being an excitatory response and the other an inhibitory response. In addition, this theory also includes a black–white mechanism, which is concerned with the perception of brightness. Please see also Opponent neuron.