Applied Science Unit One: Biology - The ECG

What is an ECG?

• ECG stands for electrocardiogram.
• Measures the action potentials/electrical impulses of the heart.
• Electro: Electricity, Cardio: Heart, Gram: Picture.
• Provides a picture of the electrical signals in the heart.

Structure of the Heart

• The heart has four chambers:
  • Atria: Receive blood from the body and lungs.
    • Smaller chambers located at the top.
  • Ventricles: Pump blood to the body and lungs.
    • Larger, more muscular chambers at the bottom.
  • Specific chambers:
    • Left and right atrium.
    • Left and right ventricle.

How ECG Works

• Electrodes are placed on the body over the chest.
  • Detect electrical impulses controlling heart muscles.
  • Machine amplifies and records, displaying them in a trace.
• Medical professionals analyze the trace for heart issues.

Components of an ECG Trace

• P Wave: Atria contract (atrial systole).
  • Atria squeeze blood into the ventricles.
• QRS Complex: Ventricles contract (ventricular systole).
  • Ventricles are larger; hence, a bigger signal.
• T Wave: Ventricles repolarize (diastole).
  • Ventricles recover and relax.

Heart Function and Control

• Pacemaker: A small cluster of cells controlling heartbeats.
  • Heart beats independently of the brain.
  • If isolated, the heart continues to beat temporarily.
  • Pacemaker generates electrical impulses causing heart muscle contractions.

Key Points to Remember

• Sequence of heart activity in ECG: P Wave → QRS Complex → T Wave.
• Understanding ECG:
  • What produces the ECG trace?
  • Describe heart activity in each ECG section.
  • Define a pacemaker and its function.