The Heart and Circulatory System

What You'll Learn

The circulatory system includes the heart, blood vessels, and blood. Arteries carry oxygen-rich blood away from the heart, and veins return oxygen-poor blood to the heart.

Key Words

response
reflex
immune system

Steps

Step 1 — Read

Review the background information on The Human Body before starting.

Step 2 — Do

Test reaction time: have a partner drop a ruler and catch it. Record the centimeter mark 10 times. Calculate your average reaction time.

Step 3 — Observe

Watch carefully for any changes and note the time.

Step 4 — Record

Create a data table to organize your measurements.

Check Your Understanding

Question 1

1 of 3

What system defends the body against germs?