Lesson 10.5 - Electrocardiogram Flashcards
How do scientists analyse the electrical activity of the heart?
by attaching electrodes to the surface of the skin
What is the resulting trace?
Electrocardiogram (ECG)
What does the pattern of the ECG tell scientists?
What is taking place in the heart.
How is a ECG trace divided?
3 sections
- P wave (atrial systole)
- QRS wave (ventricular systole)
- T wave (ventricular diastole)
x axis
Time (each division is 0.2 seconds)
y axis
potential difference (mV)
Bradycardia
If the heart rate drops below 60 bpm
What causes bradycardia?
Athletic training: increases the stroke volume of the heart
Disease: require artificial pacemaker
Tachycardia
Develop a heart rate greater than 100 bpm
What causes tachycardia?
Short-term effects
- Stress
- Fear
- Panic
- Exercise
Long-term effects
- Problems with sino-atrial node
- Surgery / drugs required
Ectopic heart beat
Extra heart beat that’s not part of the heart’s usual rhythm.
The heart contracts again before the first heart beat is finished. This is followed by short pause before the normal rhythm continues.
Risk of ectopic heart beat
Relatively common and doesn’t pose threat
Frequently: Indicate a more serious heart condition.
Atrial fibrillation
Irregular waves of electrical excitation pass over atria. This causes the atria to contract randomly and rapidly. Several hundred times a minute.
Not transmitted to the ventricles –> contract less frequently than the atria
When normal heart rhythm is disrupted?
Arrhythmia
Blood in atrial fibrillation?
Heart can not pump blood normally.
