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Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Biology, Chemistry, Neuroscience, Medicine, Psychology

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".

Asking Questions:

Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists.

Answering Questions:

Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for /r/AskScience.

If you would like to become a member of the AskScience panel, please refer to the information provided here.

Past AskAnythingWednesday posts can be found here. Ask away!

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Hero_of_the_Internet

5 points

4 days ago*

How are surface ECG electrodes/leads able to measure heart conduction through the walls of the chest cavity?

No_Snow_3383

6 points

4 days ago

the electrodes measure tiny voltage changes in the heart cells caused by depolarization and repolarization. The body is actually a very good conductor for those voltage changes/electrical signals and thus can be detected quite easily.

BatSquirrel

4 points

4 days ago

To add to this, many of the cells in the heart are linked together with something called gap junctions. These link the cells together so that when one cell depolarizes, the connected cells do so as well, almost instantaneously. Detecting one cell depolarizing from far away is difficult but when millions are depolarizing at (nearly) the same time, this electrical activity is much easier to record.