0:00:07.095,0:00:08.584
Most people will take a pill,

0:00:08.584,0:00:09.834
receive an injection,

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or otherwise take some kind of medicine[br]during their lives,

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but most of us don't know anything[br]about how these substances actually work.

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How can various compounds impact the way[br]we physically feel,

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think,

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and even behave?

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For the most part, this depends on[br]how a drug alters the communication

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between cells in the brain.

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There are a number of different ways[br]that can happen.

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But before it gets into the brain,

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any drug must first reach the bloodstream

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on a journey that can take anywhere[br]from seconds to hours,

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depending on factors like how[br]it's administered.

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The slowest method is to take[br]a drug orally

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because it must be absorbed by[br]our digestive system

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before it takes effect.

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Inhaling a drug gets it into[br]the bloodstream faster.

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And injecting a drug intravenously[br]works quickly too

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because it pumps the chemicals directly[br]into the blood.

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Once there, the drug quickly reaches[br]the gates of its destination, the brain.

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The entrance to this organ is guarded[br]by the blood-brain barrier,

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which separates blood [br]from the nervous system

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to keep potentially dangerous [br]substances out.

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So all drugs must have a specific[br]chemical composition

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which gives them the key to unlock[br]this barrier and pass through.

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Once inside, drugs start to interfere[br]with the brain's normal functioning

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by targeting its web of neurons [br]and synapses.

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Neurons are brain cells that have[br]a nucleus, dendrites, and an axon.

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Synapses are structures placed along[br]the dendrites or the axon

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which allow the exchange of [br]electrochemical signals between neurons.

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Those signals take the form of chemicals[br]called neurotransmitters.

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Each neurotransmitter plays different[br]roles in regulating our behaviors,

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emotions,

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and cognition.

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But they all work in one of two ways.

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They can either inhibit [br]the receiving neuron,

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limiting its activity,

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or excite it,

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creating a new electrochemical signal[br]that spreads throughout the network.

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Any leftover neurotransmitter usually[br]gets degraded

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or reabsorbed [br]into the transmitting neuron.

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A drug's effectiveness stems [br]from its ability

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to manipulate these synaptic transmissions[br]at different phases of the process.

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That results in an increase or a decrease

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in the amount of neurotransmitters[br]being spread.

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For instance, common antidepressants,[br]like SSRIs,

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stop the reabsorption of serotonin,

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a neurotransmitter that modulates[br]our moods.

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This effectively pushes more of it[br]into the neural network.

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Meanwhile, painkillers, like morphine,

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raise levels of serotonin [br]and noradrenaline,

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which regulate energy,

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arousal,

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alertness,

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and pleasure.

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Those same neurotransmitters also[br]affect endorphin receptors,

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reducing pain perception.

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And tranquilizers works by increasing[br]the production of GABA

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to inhibit neural activity

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putting the person in a relaxed[br]or sedated state.

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What about illegal or elicit drugs?

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These have powerful impacts on the brain[br]that we're still trying to understand.

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Crystal meth, an amphetamine,

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induces a long-lasting release[br]of dopamine,

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a neurotransmitter linked with[br]the perception of reward and pleasure.

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It also activates noradrenaline receptors,

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which increases the heart rate,

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dilates pupils,

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and triggers the body's fight[br]or flight response.

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Cocaine blocks the reuptake of dopamine[br]and serotonin,

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pushing more into the network

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where they boost energy,

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create feelings of euphoria,

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and suppress appetites.

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And hallucinogenic drugs have some[br]of the most puzzling effects.

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Substances like LSD,

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mescaline,

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and DMT

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all block the release of serotonin,

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which regulates mood and impulsivity.

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They also have an impact [br]on the neural circuits

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involved in perception, learning,[br]and behavioral regulation,

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which may explain why these drugs[br]have such powerful impacts.

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Even if some of these [br]effects sound exciting,

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there are reasons why some of these drugs[br]are highly controlled and often illegal.

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Drugs have the power to alter [br]the brain's chemistry,

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and repeated use can permanently[br]rewire the neural networks

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that support our ability to think,

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make decisions,

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learn,

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and remember things.

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There's a lot we still don't know [br]about drugs and their effects,

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both the good and the bad.

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But those we do know about are the ones[br]we've studied closely,

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and turned into effective medicines.

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As our knowledge grows about drugs[br]and the brain,

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the possibilities will also increase

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for treating the many medical problems[br]that puzzle researchers today.