episode46

046 How Adrenaline and Acetylcholine Affect Heart Rate

Leslie Samuel IBTV, Physiology, The Circulatory System 63 Comments

In this episode, Leslie discusses the effect of adrenaline and acetylcholine on heart rate. These two modifies the conductance of the ions across the membranes of the cells of the SA node causing either an increase or a decrease in heart rate.

Watch and learn how it all works.

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 and in this episode, Episode 46, I’m going to talk about how adrenaline and acetylcholine affect heart rate. So, let’s get right into it.

In the last episode, Episode 45, we looked at this slide where I showed that in the SA node, we have a pacemaker potential that results in a spontaneous signal so that we have the heart beating in response to these action potentials that are automatically generated in the SA node.

If you haven’t looked at Episode 45, I would recommend for you to pause this right now and go and watch Episode 45 so that you’re going to get a full understanding of what we’re going to be talking about.

Let’s go to the next slide. I’m sure you’ve all been in situations where, let’s say you’re doing something and someone jumps up behind you and scares you. What happens? Your heart starts beating faster. The reason it starts beating faster is because adrenaline is released from the adrenal gland that’s located above the kidneys. When that adrenaline is released, that causes the conductance in the pacemaker cells to change. As you can see here, we have an increased conductance for sodium and calcium ions. That is going to cause those to rush into the cell much faster.

It’s going to look a little different than what we looked at before because the membrane potential is going to increase significantly faster so that we’re going to get a faster action potential. So, it might look something like this. As you can see, the signal happens much faster. Forgive my sloppy drawing here. So, we have signals being produced much faster and the heart rate increases. If you remember from the last one that I showed, I was able to show two action potentials on this. But, because sodium and calcium ions are rushing in much faster, the signals are going to be generated much faster because it’s going to reach the threshold much faster and we get an increased heart rate. So, that’s adrenaline.

Now, there’s an opposite effect where instead of adrenaline being released, we have acetylcholine being released. I didn’t plan for the acetylcholine to come in as a flame but, it did for some reason.

What happens when acetylcholine is released? As you can see up here, the conductance for potassium is going to increase significantly. You should know that potassium wants to leave the cell. So, this is going to increase hyperpolarization and is going to slow down depolarization.

What’s going to happen is, instead of this rapid depolarization, we’re going to get a significantly slower depolarization so that, it takes much longer to reach the threshold. When it reaches the threshold, the usual process happens: voltage-gated calcium channels open and calcium rushes in to the cell. Then, we have our depolarization. Then, this process continues.

But, as you can see here, depolarization is much slower than over here. Here, depolarization is sped up because sodium and calcium are rushing into the cell much faster in response to adrenaline. Here, it’s going to be much slower because more potassium is leaving the cell causing depolarization to slow down and we get a slower heart rate.

Faster heart rate in response to adrenaline; slower heart rate in response to acetylcholine.

That’s pretty much it for this video. As usual, you can visit the website at Interactive-Biology.com for more Biology videos and all of the other resources we’re putting together over there. This is Leslie Samuel. That’s it for this video and I’ll see you on the next one.

Comments 63

  1. InteractiveBiology

    @petercourt Yes, that’s correct. That’s what I said in the video. When it reaches the threshold, Calcium channels open, resulting in Calcium rushing in. Sodium is involved in the pacemaker potential primarily and how the membrane depolarizes to reach the threshold, but the overwhelming effect is due to Calcium causing the action potential. Hope that answers your questions!

  2. InteractiveBiology

    Yes, that’s correct. That’s what I said in the video. When it reaches the threshold, Calcium channels open, resulting in Calcium rushing in. Sodium is involved in the pacemaker potential primarily and how the membrane depolarizes to reach the threshold, but the overwhelming effect is due to Calcium causing the action potential. Hope that answers your questions!

  3. petercourt

    Isn’t the upward deflection of an action potential in the SAN a result of the inward movement of calcium ions, rather than sodium ions?

  4. InteractiveBiology

    Yes, that’s correct. That’s what I said in the video. When it reaches the threshold, Calcium channels open, resulting in Calcium rushing in. Sodium is involved in the pacemaker potential primarily and how the membrane depolarizes to reach the threshold, but the overwhelming effect is due to Calcium causing the action potential. Hope that answers your questions!

  5. Daniella

    I really cant thank you enough for making these videos! I can sit in a lecture for an hour and a half and come out with nothing but I watch your videos for 10 minutes and its all there. Thank you! Thank you! Thank you!

    Will you be covering any of the following in the neat future:
    Immune System
    Respiratory System
    Urinary System
    Digestive System

    Thank you again for the work you do!

    ~Daniella

    1. Post
      Author
      Leslie

      Thank you so much for your comment. It gets me excited to know that the videos are helping people so much. That’s just SUPER AWESOME!

      In terms of those topics, the truth is – I plan to cover EVERYTHING, lol. I want this to be the biggest biology resource site in the world.

      However, it will definitely take a SIGNIFICANT amount of time to get it all done. I’m doing the circulatory system now, then will move on to the respiratory and then Urinary System (I think). I’m going through a sequence so that everything can flow in a very logical way.

      Glad to have you as a visitor and I hope that you continue to find a ton of value in the videos I’m going to posting in the future. Btw, I’m also going to be including a bunch of other resources to complement the videos. Some of it should be coming out pretty soon :)

  6. InteractiveBiology

    Yeah and that was a mistake. Maybe I need to be burning everything in my videos from now on. Keeps things interesting – LOL.

  7. kay

    Hi Interactive biology,

    I really thank you so much for your video. I really gald to found you here. I was so lost in my assignment to looking for idea in websites and accidentally found yours. If possible, pls kindly help my assignment, and I would like to get idea from you for how I going to write and the flow for my topic. If you can help, pls kindly email me and i will send my assignment topic to you immediately. if you have gmail, I would like to discuss with you by gtalk. Pls help me.

    kay

    1. Post
      Author
      Lrsamuel

      Hi Kay,

      Glad to know you are finding value in the site. I hope you continue to find a massive amount of value in it.

      In terms of your assignment, that’s beyond the scope of what I offer here. I can only focus on so much to be able to have the greatest impact.

      I do wish you all the best with it though. I would recommend doing google searches about the topic and seeing what you can come up with.

      All the best!

      Leslie

  8. Janny de Wit

    Dear Leslie,

    I now understand the supressive effect of acetylcholin and stimulating effect adrenalin on the heart rate.
    In case of the digestive system, acetylcholin has a stimulating effect and adrenalin supresses digestion. In fact the transmitters have an opposite effect in relation to heart rate. How can you explain this?

    1. Post
      Author
      Lrsamuel

      There are two factors that determine the effect of a neurotransmitter. 1) The Neurotransmitter itself and 2) The receptor that it binds to. One neurotransmitter can have one affect on a cell if it binds to a specific kind of receptor and a totally different effect on another cell if it binds to another kind of receptor. It all depends on how that neurotransmitter is built to respond. Hope that helps!

  9. Tuatara

    Hi Leslie,
    thank you so much for your videos, you’re doing a great job!

    Talking about this video, I’ve a question: with the release of Ach, the conductance for K+ increases, but it’ s always lower than the Na+ one, isn’t it? Otherwise we can’t have depolarization, as Ca2+ rushes into only after the threshold. Is it correct?

    Thanks again!

    P.S. I apologize for my grammar mistakes, English is not my language :)

    1. Post
      Author
      Lrsamuel

      Hi Tuatara, that is correct. Depolarization happens after the Membrane potential reaches threshold, so enough Na+ has to come in in order for that to happen. Na+ conductance has to be greater than K+ conductance in order for the Membrane potential to reach threshold.

  10. Estrellita Calaro

    How does high serum calcium affects heartbeat? How about high serum potassium? Pls explain. I understand that calcium released by sarcoplasmic reticulum produced contraction of of the heart muscle but I do not understand how extracellular calcium and/or extracellular potassium affects heartbeat. Pls explain. Thanks.

    1. Post
      Author
      Lrsamuel

      Excess Potassium levels would decrease the heart rate because that’s going to slow down depolarization in the SA node. Check out my video that deals with the SA node and you’ll see how Potassium is involved in determining heart rate.

      Excess extracellular calcium will result in spastic contraction of the heart, because of how Calcium is involved in contraction. Check out the video on the Contraction of the Heart.

      Hope that helps!

  11. KurikuShot

    Thank you very much for this video. I’m doing a question on how Adrenaline increase heart rate but all the books I read merely state that it does and doesn’t explain it. This is exactly what I’m looking for and in extremely comprehensive terms too!

  12. KurikuShot

    Thank you very much for this video. I’m doing a question on how Adrenaline increase heart rate but all the books I read merely state that it does and doesn’t explain it. This is exactly what I’m looking for and in extremely comprehensive terms too!

  13. KurikuShot

    Thank you very much for this video. I’m doing a question on how Adrenaline increase heart rate but all the books I read merely state that it does and doesn’t explain it. This is exactly what I’m looking for and in extremely comprehensive terms too!

  14. mortdepeur13

    i remember all the adrenaline i had when i was getting panic attacks. but they are not dangerous ;) the sensation is very scary and you think you are dying everytime when you freak out. But when you have fun with the fear it feels awesome and you feel like powerful. its hard to explain lol

  15. mortdepeur13

    i remember all the adrenaline i had when i was getting panic attacks. but they are not dangerous ;) the sensation is very scary and you think you are dying everytime when you freak out. But when you have fun with the fear it feels awesome and you feel like powerful. its hard to explain lol

  16. abrara321

    gd job my teacher . i have a question , you said that adrenaline released when we get scary, what about acetylcholine what causes it to be released ? ?

  17. SamGuthrie1977

    Thanks! Great video — this is exactly what I was looking for concerning Acetylcholine’s effects on heart rate.

  18. Justin Nicholai

    I wish my lecturers provide much more interesting classes, like you do. God bless you Leslie, thank you :) Worth subscribing.

  19. Sasidhar Mittapalli

    Thank you that was just perfect explanation i was looking for. You din’t mention when acetlycholine will be released?

  20. richaisdbest

    Hi…i have a question…dosent hyperpolarisation occur beyond the RMP ?? In the depiction the hyperpolarisation was not shown or i am lacking some concept here..please correct me if i am wrong…on the whole a very nice video!

  21. CuttlefishPi

    I think it has to do with the sympathetic and pathetic nervous systems, or with the amount of CO2 in the blood. Google it.

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