Why is a datalogger better than counting a pulse by hand?

A datalogger records continuously and removes human counting errors. Readings can be taken during exercise and displayed as a graph straight away.

How large is the voltage an ECG detects at the skin?

The ECG signal at the skin is only about 1 mV. The signal must be amplified many times before it can be displayed.

Why do ECG recordings pick up interference, and how is it reduced?

Muscle movement and nearby mains equipment produce voltages as large as the heart's signal. The patient lies still, and electronic filters remove the 50 Hz mains frequency.

CCEA A-Level Life and Health Sciences 0008

Experimental Techniques

Topic overview Standard solutions, titrations and qualitative tests Rates of reaction and organic preparations Physics measurements: oscillations, resistivity, lenses and critical angle Biological tests, colorimetry, chromatography and osmosis

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Topic overview Volumetric analysis in industry and healthcare Applied titrations of vinegar, indigestion tablets and bleach Redox titration of iron tablets and evaluating titrations Principles of colorimetry Colorimetric analysis of copper ore, aspirin and iron Thin-layer chromatography and its uses Visualising chromatograms and identifying painkillers and pigments Calorimetry and combustion Molar enthalpy and bond energy calculations Qualitative tests for cations and gases

Enabling TechnologyDouble Award

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Medical Physics

Heart activity experiments and EEG traces

3 things to know
A2 3

Overview

Pulse sensors and dataloggers, ECG voltage, interference and a heart rate calculation, EEG alpha, beta, theta and delta waves, spike-and-wave patterns, and EEG changes in injury and disease.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

How can heart activity be monitored in a simple school experiment?

Key term

How does a fingertip pulse sensor detect each heartbeat?

Key term

Compare a pulse sensor with an ECG as a way of monitoring the heart.

Questions from this subtopic

Each one with the model answer underneath.

1
How can heart activity be monitored in a simple school experiment?
Model answer
A pulse sensor clipped to a fingertip or earlobe detects the change in blood volume with each beat. A datalogger records the pulse rate at rest and after exercise.
2
How does a fingertip pulse sensor detect each heartbeat?
Model answer
The sensor shines light into the fingertip and a photodetector measures how much returns. Each pulse of blood absorbs more light, giving a regular rise and fall in the signal.
3
Compare a pulse sensor with an ECG as a way of monitoring the heart.
Model answer
A pulse sensor shows only the rate and regularity of the pulse. An ECG records the heart's electrical activity, so it can also reveal conduction problems and damage to heart muscle.
4
Why is a datalogger better than counting a pulse by hand?
Model answer
A datalogger records continuously and removes human counting errors. Readings can be taken during exercise and displayed as a graph straight away.
5
How large is the voltage an ECG detects at the skin?
Model answer
The ECG signal at the skin is only about 1 mV. The signal must be amplified many times before it can be displayed.
6
Why do ECG recordings pick up interference, and how is it reduced?
Model answer
Muscle movement and nearby mains equipment produce voltages as large as the heart's signal. The patient lies still, and electronic filters remove the 50 Hz mains frequency.

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