WEBVTT

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To alter our behavior or mental processes, a drug must first enter our bloodstream

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through ingestion, inhalation, absorption, or injection.

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Once in the bloodstream, psychoactive drugs alter our psychological processes

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by affecting the nervous system, particularly the synapse.

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Then over hours, the influence of the drug gradually wears off

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as the liver produces enzymes that metabolize the drug.

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An agonist in general increases the effect of neurotransmitters.

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Some drugs act as mimics binding and acting like the neurotransmitter, like in the drawing here.

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So the drug adds to whatever amount of neurotransmitter is being released.

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It is as if more neurotransmitter is being released.

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An antagonist does the opposite, reducing the activity at a neurotransmitter.

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Some drugs bind but then block the binding of the neurotransmitter, as shown here.

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If the neurotransmitter cannot bind, then the neurotransmitter cannot have effect.

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Now, let us review some sample drugs.

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After the review, you will be asked if the drugs are agonists or antagonists.