Week 5 · Chapter 3: 3-3 How Absorption Works, Let’s Expand (the liver), Review & Practice; Chapter 4 Circulation and Excretion: 4-1 Heart and Blood · 3 lessons
3
The heart, the blood and your pulse
Science P6: Term 1, Chapters 3–4, pp. 30–37
GoalDescribe the heart as a pump and measure a pulse safely.
New words
heart · the muscular pump that moves blood around the bodypulse · the beat felt in an artery each time the heart pumpsblood · the liquid that carries oxygen, nutrients and wastes
Explanation
The heart is a strong muscle that works as a pump. It has two sides. One side pumps blood to the lungs, where it takes oxygen and gives away carbon dioxide. The other side pumps blood to the rest of the body. The blood carries oxygen and nutrients to every part and brings back carbon dioxide and other wastes. Then it returns to the heart, and the journey starts again. Each time the heart beats, an artery stretches a little; this is the pulse. To find it, place two fingers (not the thumb) on your wrist. Count for 30 seconds and double the number. A child’s resting pulse is usually between 70 and 100 beats a minute. Blood is red; it is not blue inside the body.
Worked examples
Count in 30 seconds
Beats in one minute
38
76
Karim finds his pulse and counts 38 beats in 30 seconds. He doubles it: 38 × 2 = 76 beats a minute. This is a usual resting pulse.
After 20 gentle step-ups (only if well), Nour counts 46 beats in 30 seconds, so her pulse is 92 beats a minute. It is faster because the muscles need more oxygen.
A doctor listens to a heart to learn if it beats steadily. The heartbeat is a sound; the pulse is the beat we feel.
Class activity
Pulse count. With a grown-up, find your pulse with two fingers on the wrist. Count for 30 seconds and double it. Write it. If you are well, do 20 gentle step-ups and count again. No competitions and no targets.
Practice
1
How many sides does the heart have?
Two: one sends blood to the lungs, one to the body.
2
A pulse count of 35 in 30 seconds means how many beats in a minute?
70.
3
Why is the pulse faster after exercise?
The muscles need more oxygen, so the heart pumps faster.
