018 Agonists and Antagonists

018 Agonists and Antagonists

Leslie Samuel IBTV, The Nervous System 119 Comments

In this video, watch as Leslie explains how agonists and antagonists affect the receptor sites of the cell.

Enjoy!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive Biology TV, where we’re making biology fun! My name is Leslie Samuel. In this episode, Episode 18, I’m going to be talking about agonists and antagonists. It almost sounds like a plot for a movie, but it’s not a movie, unless it’s a movie happening inside your body. Anyhow, for today, let’s get into what we’re going to be talking about.

The first thing we’re going to talk about is “What is an agonist?” An agonist is a molecule that mimics the effect of a neurotransmitter, so it does what that neurotransmitter would normally do. An example of that would be succinylcholine mimics the neurotransmitter acetylcholine. So what I’m going to do is I’m going to draw the receptor here, and here we have the cell membrane of the neuron. I’m going to draw it a little different than I’ve been drawing it before. I’m going to have these as the receptor sites. This is where the acetylcholine normally binds to the nicotinic receptor.

I’m going to draw acetylcholine here, but I’m not going to draw it coming here. What I’m going to do is I’m going to draw something that’s slightly different, let’s just say it’s a different color. It’s a similar shape to acetylcholine, and we’re going to call this succinylcholine. When that comes here and it binds to the receptor, same thing here, it comes and it binds to the receptor, the channel opens, which is what it would normally do if acetylcholine binds. And then, sodium ions on the outside end up coming inside the cell. So this would be an example of an agonist. It’s not acetylcholine, it’s something else, and let’s say, in this case, it’s succinylcholine, and that comes, binds to the receptor and causes a similar response. That is an agonist.

Now, let’s look at what an antagonist is. You can probably guess just by reading the word, but an antagonist is a molecule that opposes the effect of a neurotransmitter. So it does the exact opposite. An example of that would be curare, which is an antagonist to acetylcholine that can actually block the binding sites for acetylcholine. So here, we have our nicotinic receptor again, and it’s in the membrane of the cell, and here we have the binding sites.

Out here, we have acetylcholine that wants to bind. However, we have something else that’s around that’s not exactly like acetylcholine and let’s say that its shape looks something like this. That binds to the receptor, and what that does is it blocks the receptor site. So acetylcholine wants to bind and it wants to cause that channel to open, but it’s being blocked so that it cannot bind, and it cannot open the channel for sodium to come in. This would be an example of what curare does. It’s an antagonist, and in fact, curare can cause muscles to become paralyzed because they cannot be activated and sodium cannot rush into the cell, exciting the cell, and exciting the muscle to contract. So that can be a serious thing if you have curare binding to these receptor sites.

That’s really all for this video. I hope you understand the difference between an agonist and an antagonist. If you have any questions or comments about that, go ahead and leave them below. I’ll be happy to answer your question, and maybe even make a follow-up video answering your specific question. That’s it for this video, and I’ll see you on the next one.

Comments 119

    1. Post
      Author
      Leslie

      Hi Tara,

      That’s an excellent question. You got it right. It all has to do with having the right shape to fit into the binding site so that it’s able to trigger a response.

  1. DatNigerian

    Dude you don’t know how grateful i am that you are out there breaking down
    this terms and concepts. am currently taking a physiology class and its a
    killer to comprehend but your illustration makes it easier to grasp and
    understand. THANK YOU

  2. TimmysMummy

    Hey :) not only do your videos help me understand but also REMEMBER this stuff, which is the important part for the exams isnt it!! PLEASE dont stop making these videos.

  3. TimmysMummy

    Hey :) not only do your videos help me understand but also REMEMBER this stuff, which is the important part for the exams isnt it!! PLEASE dont stop making these videos.

  4. Jourdyn

    You videos are awesome for helping with my cell biology class! My teacher just does not explain this stuff as well as you do! Thanks!

    1. Post
      Author
      Leslie

      That’s Awesome Jourdyn,

      Glad to know you are finding value in the videos. I plan on expanding a lot on what’s here, so make sure to stay tuned :)

      All the best!

  5. 2joann

    Suppose your given a graph that indicates the frequency of action potentials firing. There are 4 drugs and two bar graphs for each drug indicating the frequency of stimulation and no stimulation. If a drug shows that there’s an increase of stimulation of Drug A, but also an increase in no stimulation. Should we assume this molecule A is an antagonist? Based on your video, this is what I have analyzed.

  6. 2joann

    Suppose your given a graph that indicates the frequency of action
    potentials firing. There are 4 drugs and two bar graphs for each drug
    indicating the frequency of stimulation and no stimulation. If a drug shows
    that there’s an increase of stimulation of Drug A, but also an increase in
    no stimulation. Should we assume this molecule A is an antagonist? Based on
    your video, this is what I have analyzed.

  7. InteractiveBiology

    @2joann I’m a little confused by what you mean with an increase in
    stimulation and an increase in no stimulation. Can you clarify?

  8. InteractiveBiology

    Paroxetine is an antagonist to the neurotransmitter serotonin. Ketamine is
    an antagonist that acts on the NMDA receptor, which is a receptor for
    glutamate.

  9. hally003

    Brilliant!! Thank you SO much :)

    Can anyone help me understand the effects of an agonist at glutamate receptors?

  10. MultiverseQueen

    Thank you SO SO much!! I seriously cannot tell you how helpful this is to me right now. I’m at my wits end trying to mentally go through the process. I’ll search through the vids to see if you cover everything I’m trying to learn like the specifications on things like the SSRIs etc.

  11. MultiverseQueen

    Thank you SO SO much!! I seriously cannot tell you how helpful this is to me right now. I’m at my wits end trying to mentally go through the process. I’ll search through the vids to see if you cover everything I’m trying to learn like the specifications on things like the SSRIs etc.

  12. InteractiveBiology

    You are very much welcome. Glad to know it’s helping. I have many others. I haven’t covered SSRIs as yet, but that will probably come at some point. All the best!

  13. InteractiveBiology

    @ta88iv All questions are answered in the Interactive Biology community forums from now on. Go to the website in the description and then visit the community. This is to make it as efficient as possible as we have multiple people over there to help answer questions.

    All the best

  14. InteractiveBiology

    All questions are answered in the Interactive Biology community forums from now on. Go to the website in the description and then visit the community. This is to make it as efficient as possible as we have multiple people over there to help answer questions.

    All the best

  15. InteractiveBiology

    Unfortunately, Leslie won’t be able to answer any specific questions as he is busy creating videos and content for the site. He will get to more Biology topics so, please stay tuned for more!

  16. InteractiveBiology

    @msss432 Hi! I’m so sorry, but Leslie is busy with a lot of stuff right now. He just doesn’t have the time to be able to go through each mail he gets but, he’s working on more videos and he might just touch more about this topic. So, please stay tuned for more! You can try to go to our Facebook Fan Page community, too. There are some who would answer Biology inquiries from there.

  17. InteractiveBiology

    Hi! I’m so sorry, but Leslie is busy with a lot of stuff right now. He just doesn’t have the time to be able to go through each mail he gets but, he’s working on more videos and he might just touch more about this topic. So, please stay tuned for more! You can try to go to our Facebook Fan Page community, too. There are some who would answer Biology inquiries from there.

  18. InteractiveBiology

    Hi! I’m so sorry, but Leslie is busy with a lot of stuff right now. He just doesn’t have the time to be able to go through each mail he gets but, he’s working on more videos and he might just touch more about this topic. So, please stay tuned for more! You can try to go to our Facebook Fan Page community, too. There are some who would answer Biology inquiries from there.

  19. xamandaxgatewayx

    @xamandaxgatewayx so when you take a certain drug it can either work as an agonists by enhancing the effect of a neurotransmitter, or it can work as an antagonist and prevent the neurotransmitter from working.

  20. xamandaxgatewayx

    so when you take a certain drug it can either work as an agonists by enhancing the effect of a neurotransmitter, or it can work as an antagonist and prevent the neurotransmitter from working.

  21. dieurobotica

    @msss432 hi, I only know about curare…I was taught that its an arrow poison…so, imagine one trying to shoot an animal and all of a sudden, ‘mistakenly’ shoots a person around…it will act… (thats the little I know about how it can get there)…

  22. dieurobotica

    hi, I only know about curare…I was taught that its an arrow poison…so, imagine one trying to shoot an animal and all of a sudden, ‘mistakenly’ shoots a person around…it will act… (thats the little I know about how it can get there)…

  23. dieurobotica

    hi, I only know about curare…I was taught that its an arrow poison…so, imagine one trying to shoot an animal and all of a sudden, ‘mistakenly’ shoots a person around…it will act… (thats the little I know about how it can get there)…

  24. Yorreh20

    @msss432
    Succinyl-choline (the antagonist) is a medication used in Healthcare, especially in anesthesiology (where people are sedated for surgery). It causes the muscles to relax so it’s easier to work with the body (i.e. intubation, cutting through muscle, opening the cuts)

    The antagonist is also a type of medication, lots of examples here. It also causes relaxation, but does so in a different manner (as explained in the video).

  25. Yorreh20

    Succinyl-choline (the antagonist) is a medication used in Healthcare, especially in anesthesiology (where people are sedated for surgery). It causes the muscles to relax so it’s easier to work with the body (i.e. intubation, cutting through muscle, opening the cuts)

    The antagonist is also a type of medication, lots of examples here. It also causes relaxation, but does so in a different manner (as explained in the video).

  26. Yorreh20

    Succinyl-choline (the antagonist) is a medication used in Healthcare, especially in anesthesiology (where people are sedated for surgery). It causes the muscles to relax so it’s easier to work with the body (i.e. intubation, cutting through muscle, opening the cuts)

    The antagonist is also a type of medication, lots of examples here. It also causes relaxation, but does so in a different manner (as explained in the video).

  27. Michele

    Leslie,
    Thank you so much for explaining and drawing out the differences between an agonist and an antagonist. You did an awesome job at breaking this concept down and now I can understand it completely! Sincerely,
    Michele

    1. Post
      Author
  28. lovejoy44ie

    Thank you so much, we are currently studying this in college, and to be honest i was very confused, but you made it very interesting, and i finally understand what is actually going.. Thank you again :)

  29. lovejoy44ie

    Thank you so much, we are currently studying this in college, and to be honest i was very confused, but you made it very interesting, and i finally understand what is actually going.. Thank you again :)

  30. liddlesez

    It’s my understanding is agonist and antagonists (same compounds can be both) depends on the effect they are going to have. A drug that might act as an antagoist for one compound might act as an antagonist. Some can be in the body, or administrated drugs via oral, iv and other routes of administration. I think that’s the best way to exam it. Have a read of some pharmcology text books :)

  31. liddlesez

    It’s my understanding is agonist and antagonists (same compounds can be both) depends on the effect they are going to have. A drug that might act as an antagoist for one compound might act as an antagonist. Some can be in the body, or administrated drugs via oral, iv and other routes of administration. I think that’s the best way to exam it. Have a read of some pharmcology text books :)

  32. Linda

    Thank you Leslie, you are the best!!!! Btw, after watching some of your videos onhow action potential works in our brain. And other videos relating to the physiology of the brain I Aced my exam :)
    Thank you for all you do. I’m always watching and looking forward for more of your videos

    1. Post
      Author
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    My pal had been obese. He converted his body from 283 lbs of pure fat into 200lbs of purely natural lean muscle. Everyone was shocked. I just signed up personally because I wanna strengthen. He made use of the Muscle Building Bible (Look in Google)…

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