The Circulatory System
Measuring Pulse Rate, Calculating Heart Rate During Exercise & Blood Pressure Interpretation
🫀 What Is the Circulatory System?
The circulatory system (also called the cardiovascular system) is the body's transport network. It moves oxygen, nutrients (like glucose), hormones, and waste products (like carbon dioxide) to and from every cell in your body.
The system has three main components:
❤️ The Heart
A muscular pump with 4 chambers (2 atria, 2 ventricles) that contracts rhythmically to push blood through the body.
🔴 Blood Vessels
Arteries carry blood away from the heart; veins return blood to the heart; capillaries allow gas exchange at tissues.
🩸 Blood
The fluid that carries oxygen (via red blood cells), fights infection (white blood cells), and contains platelets and plasma.
💓 Pulse Rate & Heart Rate
What Is a Pulse?
Each time the heart beats, it pumps blood into the arteries, causing them to briefly stretch and bulge. This brief bulge that you can feel is called a pulse. The number of pulses per minute gives a good estimate of your heart rate.
How to Measure Your Pulse
📍 Pulse Points
- Radial artery — inside of the wrist (thumb side)
- Carotid artery — side of the neck
Place your index and middle fingers (never your thumb — it has its own pulse!) on the pulse point and count the beats.
🔢 The Mathematics of Measuring
Full method: Count beats for 60 seconds = beats per minute (bpm)
Shortcut 1: Count for 30 seconds × 2 = bpm
Shortcut 2: Count for 15 seconds × 4 = bpm
$$ \text{Heart Rate (bpm)} = \text{Beats counted} \times \frac{60}{\text{Seconds counted}} $$
Resting Heart Rate (RHR)
| Category | Resting Heart Rate |
|---|---|
| Average Adult | 60–100 bpm |
| Well-Trained Athlete | As low as 40 bpm |
| Typical Grade 8 Student (age 13–14) | ~70–85 bpm |
A lower resting heart rate generally indicates better cardiovascular fitness — the heart is so efficient that it pumps more blood per beat.