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Para- and Sympathetic Control of the Heart Rate – Heart Rate and Electricity

by Thad Wilson, PhD
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    Now, what controls SA node rate. Because you know that your heart rate can go slower than 60, they can go faster than 100, so what controls that process? Nerves control it to the greatest degree. So, we have things like the parasympathetic nerve system. So, here, you have cranial nerve number IX – sorry, number X which is the vagus nerve. The vagus nerve releases acetylcholine. Acetylcholine then binds to a muscarinic receptor on the SA node. What this happens, at this point, is it slows down heart rate. So, the more vagal the response, the slower the heart rate. We call that negative chronotropy. Where does that come from? Negative just means less than normal. Chronotropy is what we call heart rate. It seems like a fancy word for heart rate, but you have to know it. How do you get a faster heart rate? There, it is a sympathetic nervous system response. This is your classic fight or flight; or like what I like to call it, fight, flight or maybe it’s simply flight and aggressive conflict mediation. Whatever you do, you know that it's a process in which you’re speeding up the heart. This is a beta-adrenergic response where you have norepinephrine being released from presynaptic terminals, binding to beta-1 adrenergic receptors to speed up the heart. We call that positive chronotropy. Positive means higher than normal. Chronotropy again is our name for heart rate. So, you can see here how the nervous system both speeds up and slows down the heart. All through its actions, only on the SA node, in this case. So, now let's take a couple of minutes and talk through exactly how the sympathetic and parasympathetic nervous systems actually control heart rate because this is a complex process. You know that...

    About the Lecture

    The lecture Para- and Sympathetic Control of the Heart Rate – Heart Rate and Electricity by Thad Wilson, PhD is from the course Cardiac Physiology.


    Included Quiz Questions

    1. Increase in the rate of phase 4 depolarization
    2. Increase in the threshold potential to a less negative value
    3. Greater absolute amount of repolarization
    4. Lower or more negative shift in resting membrane potential

    Author of lecture Para- and Sympathetic Control of the Heart Rate – Heart Rate and Electricity

     Thad Wilson, PhD

    Thad Wilson, PhD


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    AMAZINGLY HELPFUL
    By Vana P. on 23. January 2017 for Para- and Sympathetic Control of the Heart Rate – Heart Rate and Electricity

    Love the fact that the topic is split into bitesize clips and the focus is on understanding first then learning second.