📊 Summary Table of ECG Waves
| ECG Part | What It Shows | Significance |
| P Wave | Atrial contraction begins | SA node is working |
| PR Segment | Atria done contracting, signal travels to AV | Shows time delay |
| QRS Complex | Ventricular contraction | Big heartbeat; should be strong |
| ST Segment | End of contraction | Check for heart attack/ischemia |
| T Wave | Ventricles resetting | Ready for next beat |
| QT Interval | Total action time of ventricles | If long, may be dangerous |
🧠 Final Thoughts: What Students Should Remember
- The heart’s rate is normally controlled by the pacemaker but influenced by the brain.
- An ECG shows how the heart is functioning electrically, just like how a sound wave shows how someone is speaking.
- Each wave in an ECG tells us what part of the heart is working and if there is any problem.
- ECG is a non-invasive, painless test used every day to save lives.
🩸 11.2 – Blood Vessels: Transport System of the Body
Think of your body as a city and your blood as vehicles carrying food, oxygen, and waste. Just like a city has roads, your body has blood vessels. These vessels transport blood everywhere—from the tips of your toes to the top of your head.
🚗 Three Main Types of Blood Vessels
Your circulatory system has three types of roads (vessels):
- Arteries – Carry blood away from the heart.
- Capillaries – Connect arteries and veins; allow exchange of materials.
- Veins – Carry blood back to the heart.
Let’s now understand each of these in detail.
1. Arteries – The Strong Highways
📌 What are arteries?
Arteries are blood vessels that carry blood away from the heart. Almost all arteries carry oxygen-rich blood, except pulmonary arteries, which carry oxygen-poor blood to the lungs.
💡 Real-life example: Imagine you fill a balloon and squeeze it—water gushes out with pressure. The heart also pumps blood out with high pressure, so arteries must be strong and elastic to handle that pressure.