In this video I describe how psychoactive drugs can influence neural communication by passing through the blood-brain barrier and acting as either agonists or antagonists. The brain also responds to this influence via neuroadaptation which can create tolerance and withdrawal to certain drugs. In addition to this physiological aspect of addiction, drugs can also carry psychological aspects of addiction, particularly when used to cope with certain emotions or situations.

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Video Transcript

Hi, I’m Michael Corayer and this is Psych Exam Review. In this video and the next video we’re gonna look at the relationship between drugs and consciousness. Now when we talk about drugs here we’re gonna be referring to psychoactive drugs and this refers to drugs that are able to alter brain chemistry. Now when we think about altering brain chemistry this can come from medications or it can include drugs that are used recreationally like alcohol or caffeine but an important point in that most things can’t get into the brain. Altering the brain is not easy to do and this is because we have the blood-brain barrier.

So this is like the security network that keeps most things from being able to get into the brain. So it allows vital nutrients into the brain but it blocks pretty much everything else and this is good because things like brain viruses and brain infections are incredibly rare. So even though you might have an infection in your body it’s generally unable to get into your brain where it would have really major consequences.

Now the downside of this is that when an infection does get into your brain it’s really hard to treat it because most medications can’t get through this blood-brain barrier. So we can’t get them into the brain to fight the infection but there are some molecules that are able to pass through this blood-brain barrier and these are going to be found in these psychoactive drugs. So these drugs are able to get into the brain where they can influence neural communication.

This brings us to the two main ways that a drug can influence neural communication and I talked about this in a previous video. So some of this is review and this is the distinction between an agonist and antagonist so I want to go over this one more time and think about the ways that drugs can be either an agonist or antagonist. So an agonist refers to a drug that increases the effects of a neurotransmitter; it boosts the message that a neurotransmitter is sending. So if we want to boost the message of a neurotransmitter there’s three main ways that we could do that. The first thing we could do is we could mimic the neurotransmitter. So if we act like the neurotransmitter and we have the same effects as the neurotransmitter then that would essentially boost the message and I mentioned this in a previous video when we talked about the relationship between nicotine and the neurotransmitter acetylcholine because nicotine is able to effectively mimic the acetylcholine and so it causes an increase in the effects of this acetylcholine in certain areas of the brain. So that’s one way we could boost a neurotransmitter’s message.

Another way is that we could stop the neurotransmitter from being broken down. So we could block the removal of the neurotransmitter, either from being taken back up into the presynaptic neuron, we could block the reuptake, or we could do something like block an enzyme that normally breaks the neurotransmitter down. And what this would do is it would allow the neurotransmitter to spend more time in the synapse and this would increase the message that the neurotransmitter is trying to send.

And lastly we could stimulate the release of a neurotransmitter. This would also boost the message. So we could go to the presynaptic neuron and essentially force the neurotransmitter out so we can stimulate the release of the neurotransmitter and that would boost the effects of this neurotransmitter. So those are three main ways that a drug might be an agonist for a particular neurotransmitter; it could mimic the neurotransmitter, block its removal or reuptake, or it could stimulate the release of the neurotransmitter.

Now in contrast we have an antagonist drug. So an antagonist is going to have the opposite effect. What an antagonist does is it decreases the neurotransmitter’s message. And of course you can take each of these methods here and just do the opposite. So one way that an antagonist could decrease the message would be that it could mimic the neurotransmitter but not mimic the effects. What that would essentially accomplish is it would block the receptor. So you could have a drug that binds to the receptor for a particular neurotransmitter but it doesn’t do anything once it binds to it. So now the neurotransmitter can’t get to the receptor because the drug is blocking. Another thing that you could do is you could increase the removal of the neurotransmitter from the synapse. So you could have a drug that breaks the neurotransmitter down or or that stimulates an enzyme that breaks the neurotransmitter down and that would increase the removal of the neurotransmitter from the synapse. It would have less time to send its message and that would decrease the message from the neurotransmitter. And lastly we could block the release or decrease the release of a neurotransmitter from the presynaptic neuron, and of course, that would also decrease the message that the neurotransmitter is trying to send.

All right, so these are two main ways that we can divide drugs up when it comes to thinking about psychoactive drugs and their effect on neural communication. They can generally either be agonists or antagonists. Now when we think about this process of using drugs to influence our brain chemistry an important point is that the brain is responding it’s not sort of passively just being influenced by these chemicals. It also changes in response to the presence of other chemicals and this is what’s known as neural adaptation. And so neural adaptation refers to this idea that the brain is also changing in response to the presence of these other chemicals that are interfering with it, with neural communication, and so you probably know about this already because you know about tolerance to particular drugs. So if you think about a drug like caffeine if, you know, the first time you drink a, you know, a large black coffee, you know you were like shaking or something. You weren’t used to this amount of caffeine in your system and so the effects were very strong.

But if you drink that every morning you probably know that you develop a tolerance to it. What happens your brain actually changes in response to the presence of this caffeine. That’s happening day after day so that it weakens the effect, right? And so the same would be true for alcohol. If you give to people, you know, a few shots of vodka or something and one person drinks, you know, every day and the other person doesn’t drink at all, you probably see the person who doesn’t drink is going to have a stronger response to this alcohol because they haven’t built up the tolerance. And I also mentioned this when I talked about nicotine. If you smoke cigarettes, you develop a sort of tolerance to this nicotine, right? The nicotine normally stimulates this acetylcholine message but if you keep doing this over time you actually change the receptors for acetylcholine so that they’re less sensitive to the presence of nicotine and that also means that you need more nicotine to get the same effect in the same way that you might need more coffee in order to get the same stimulating effect than when you first started drinking coffee, or you need more alcohol to feel buzzed rather than when you first, you know, had one beer and you felt light-headed or something.

Ok, so that’s tolerance and we also have sort of the opposite that occurs which is withdrawal. And that is that when the drug isn’t around and your brain is used to its presence, you have some negative effects from that. So if you drink lots of caffeine every day you also know this because if you drink a lot of coffee every morning and then one morning you can’t have your coffee you go through this withdrawal. You might even get a headache from this and that’s because your brain has become dependent on this presence of caffeine to sort of have a normal level of functioning. And so when the caffeine isn’t there now suddenly you’re unable to get this level of functioning on your own. And the same would happen for cigarettes or for alcohol.

So if you were heavily addicted to alcohol and you drink every day and then you suddenly quit you have a withdrawal process where your body has been relying on the inhibiting effect of alcohol and suddenly it’s not there. You actually get overstimulated and you can have all sorts of negative effects from that which I’ll talk about in the next video.

Ok, so this brings us to the difference between physical addiction and psychological addiction. So when we’re talking about this tolerance and withdrawal, we’re talking about a physiological addiction. It’s an actual response in your body because of this neuroadaptation where you need this drug in order to get back to your sort of normal level of function. So when somebody who’s been drinking chronically for a long period of time quits alcohol they will have this physical response to this. They’ll have a withdrawal process that they’ll have to go through, but this may only last for a few days or a few weeks.

But they’ll also have a psychological aspect of their addiction and this is especially true if they’ve been using alcohol to cope with certain situations. So now it could be several months or even years later, this person, they no longer have the physiological addiction, the neuroadaptation means that they’re sort of back to normal. Their body doesn’t crave the alcohol in order to get its normal level of functioning but in certain social social situations they may still have cravings for alcohol and this is because of their psychological addiction. They’ve been using it to cope with things like social anxiety and so when they’re in a situation when they experience social anxiety of course they want to turn back to using alcohol like they did before in order to cope with this. And so another part of overcoming addiction is learning how to cope with these psychological factors, not just coping with the physiological aspects of addiction to a drug.

Ok, in the next video I’ll talk about three main classes of drugs which are depressants, stimulants, and hallucinogens, and we’ll go through a little more detail on some particular types of drugs and their effects on consciousness. I hope you found this helpful, if so, please like the video and subscribe to the channel for more. Thanks for watching!