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What is an ECG actually recording?

The line on an ECG represents electrical activity associated with your heartbeat. Understanding what produces that record helps separate a measurement of timing and rhythm from a picture of the heart’s structure.

3–5 min

Questions you could explore

  • How do electrodes on the skin produce a record of the heart’s electrical activity?

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Health and the body

How does daylight set the body’s clock?

Feeling sleepy at night involves more than counting the hours since you woke up. Internal daily rhythms respond to outside cues, with light helping coordinate the body's sense of time.

3–5 min

How does daylight set the body’s clock?

Health and the body3–5 minFeeling sleepy at night involves more than counting the hours since you woke up. Internal daily rhythms respond to outside cues, with light helping coordinate the body's sense of time.

Health and the body

How does a vaccine give the immune system a memory?

The immune system can respond differently to something it has encountered before. Vaccines make use of recognition and memory, though different vaccine types introduce the relevant information in different ways.

4–5 min

How does a vaccine give the immune system a memory?

Health and the body4–5 minThe immune system can respond differently to something it has encountered before. Vaccines make use of recognition and memory, though different vaccine types introduce the relevant information in different ways.

Health and the body

Why won’t an antibiotic treat a viral cold?

The word infection covers illnesses caused by very different organisms. An antibiotic that helps against certain bacteria has no matching target in the viruses that cause a cold.

2–3 min

Why won’t an antibiotic treat a viral cold?

Health and the body2–3 minThe word infection covers illnesses caused by very different organisms. An antibiotic that helps against certain bacteria has no matching target in the viruses that cause a cold.

What is an ECG actually recording? | Speech Topic | speaking.app