A bent-arm diagram anchors this 3-page 4th grade science worksheet on how bones and muscles work together. Students label the humerus, forearm bones, elbow joint, biceps and triceps from a word bank. Page 2 asks four questions: which muscle bends the elbow, which straightens it, what attaches muscles to bones and why muscles work in pairs. Page 3 is the answer key. It supports NGSS 4-LS1-1.
4-LS1-1
“Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction.”
Part 1 names the bones, joint and muscles of the arm, and Part 2 asks which muscle pulls to bend and to straighten the elbow.
A bent arm shows five numbered parts with pointer lines. Students pick from a word bank of five names and write one on each numbered line.
Four questions with writing lines. The first three need one word, such as biceps, triceps and tendons. The fourth asks students to explain why muscles work in pairs in a few sentences.
The five labels in order, the one-word answers and a model sentence: muscles can only pull, so a second muscle pulls the bone back the other way.
Feel it first
Have students rest a hand on the front of the upper arm while they bend and straighten the elbow. They feel the biceps tighten, then the triceps on the back, and the diagram makes sense.
Teach pull-only first
Question 4 depends on the idea that muscles can only pull. The student pages do not say it, so teach it before students reach that question.
Act it out
Ask partners to move one arm slowly and name which muscle is pulling at each moment. Then they write the answer to question 4 in their own words.
Get started today
