Monitoring Activity of the Heart

Section 1 of 6Ways of monitoring the heart

Electrocardiogram (ECG)

• Electrocardiogram (ECG) Electrodes on the skin detect the tiny electrical signals made as the heart muscle contracts.
  • A trace is produced which can show the heart rate and any irregular rhythm.

Pulse rate

• Pulse rate Each beat sends a surge of pressure along the arteries, which can be felt at the wrist or neck.
  • Counting the pulses in a minute gives the rate.

Listening with a stethoscope

• Listening with a stethoscope The 'lub-dub' sounds are made by the heart valves closing.
  • A doctor can count them and listen for unusual sounds.

Units

• Units Heart rate and pulse rate are measured in beats per minute (bpm).

Section 2 of 6Investigating the effect of exercise on pulse rate

1

Ask the volunteer to sit still for several minutes, then count their pulse for one full minute to find the resting rate.

2

Have them carry out a fixed amount of exercise, such as running on the spot for two minutes.

3

Immediately after exercise, record the pulse rate for one minute.

4

Continue to record the pulse rate every minute until it falls back to the resting value.

5

Note the time this recovery takes.

6

Repeat with the same person, or with several people, and calculate mean values to improve reliability.

Section 3 of 6Variables and safety

Type	Detail
Independent variable	Exercise (rest compared with exercising, or different amounts or intensities of exercise)
Dependent variable	Pulse rate in beats per minute, and recovery time
Control variables	Same volunteer, same type and duration of exercise, same time of day, same method of measuring pulse
Safety	Do not use volunteers with heart or breathing problems; stop if anyone feels dizzy or unwell

Section 4 of 6Interpreting the results

1Muscles work harder

• Muscles work harder During exercise the muscles respire faster and need more oxygen and glucose.

2Heart rate increases

• Heart rate increases The heart beats faster to deliver blood more quickly and to remove carbon dioxide.

3Exercise stops

• Exercise stops The demand falls, but the pulse does not drop immediately.

4Slow recovery

• Slow recovery The rate takes several minutes to return to resting level;
  • a fitter person usually recovers more quickly.

Section 5 of 6Key terms

Term	Meaning
ECG	Electrocardiogram: a recording of the electrical activity of the heart.
Pulse rate	The number of pressure surges felt in an artery each minute, equal to the heart rate.
Resting rate	The heart rate of a person who is sitting still and relaxed.
Stethoscope	An instrument used to listen to the sounds of the heart valves closing.
Beats per minute (bpm)	The unit used to measure heart rate.

Section 6 of 6Exam technique

1

Counting the pulse for only a few seconds without scaling up carefully, or taking readings of different lengths in different runs.

2

Forgetting to record the resting rate first, so there is nothing to compare the exercise results with.

3

Saying the stethoscope hears the heart 'pumping'. It picks up the sound of valves closing.

4

Giving only the heart rate after exercise and not the recovery time, which is also needed to show the full effect.