eli5: how do betablockers control ectopic heart beats?
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Quick rundown of anatomy and physiology:
1. The heart is made of special muscle cells found nowhere else in the body. Some of these cells are capable of electrically discharging completely on their own which will cause the discharge and contraction of cells nearby, then again and again so on.
2. Clusters of these auto-discharging cells are called nodes. You have nodes all over your heart. The big, main one that runs everyone’s heart is called the Sinus Node. If a heart beat comes from a series of discharges that come from the sinus node, it’s a sinus beat. If a heart beat comes from a different node, it’s an ectopic beat.
3. One of the ways the heart can speed up is through the influence of multiple chemicals which I’ll simplify as “adrenaline”. Adrenaline is the key which turns on the “get up and go” mechanisms. Adrenaline is always present in your blood at all times of the day, and the amount of it spikes up during fight/flight situations.
4. One of the receptors on the heart is the Beta receptor. It can influence the speed and force of heart muscle contraction when adrenaline connects.
So beta blockers block beta receptors (like a dimmer switch more than an on-off switch) on the heart which makes them less likely to fire as readily. The goal with ectopic beats is to make them less sensitive to adrenaline that’s floating by so the sinus node will take over. The sinus node is also affected and your heart will beat a little slower, but it’ll be the one in charge which is better than having competing nodes (like having one quarterback shouting instructions rather than two).
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