Systole and Diastole
Systole and Diastole is the two-part pumping rhythm of your heart: squeezing blood out, then filling back up.
A rubber bulb sits in a bowl of water with a tube leading to a second bowl. Squeeze the bulb, and water shoots through the tube into the second bowl. Let go, and the bulb pops open and pulls water back in from the first bowl. Your heart works the same way — it squeezes to push blood out, then relaxes to fill back up.
Explaining systole and diastole by grade level
Put two fingers on your wrist and feel that beat. Each beat has two parts. First, your heart squeezes tight to push blood out to your whole body. Then it opens wide to fill up with blood again.
Projects that explore systole and diastole
Every heartbeat sends a pressure wave through your arteries. When the heart squeezes blood out during systole, that pressure spikes. When it fills back up during diastole, the pressure drops. You can feel this two-part rhythm as a pulse — at the wrist, the neck, behind the knee, or several other sites. Comparing those pulse sites reveals how blood pressure rises and falls with each pumping phase.
A blood pressure reading captures the heart's pumping rhythm as two separate numbers. The first is systolic pressure — the force measured when the heart pumps. The second is diastolic pressure — the force measured when the heart rests and fills. To take the reading, you wrap a cuff around the upper arm and inflate it until it squeezes the brachial artery shut. As you slowly release the air, listen through a stethoscope: the first sound marks systolic pressure, and when the sounds stop, that reading is diastolic.