Muscles work in pairs

Lesson overviewBUILD · Week 4

Two muscles. Two pulling jobs.

I can explain a bend and an active straighten at the elbow.

Simplified arm diagram showing two muscles on opposite sides of the elbow joint.

Muscles work in pairsSlide 1 of 11

You Do · practiseBUILD · Week 4

Watch a bend and a straighten

Watch the adult’s card arm model.

Which pull makes the model bend?

Which pull makes it straighten?

Card arm model with two card pieces joined at an elbow pivot and strings representing muscle pulls.

Muscles work in pairsSlide 2 of 11

I Do · learn and modelBUILD · Week 4

Three things we will do

Meet the muscle pair.

Compare a bend and a straighten.

Explain which muscle contracts.

Muscles work in pairsSlide 3 of 11

I Do · learn and modelBUILD · Week 4

A model helps us see a pull

Read the slide text

Two card bones meet at a circular elbow join. An upward arrow on the forearm shows the direction of a gentle model pull. card bone elbow join gentle pull Card represents bones. The join represents an elbow. Loose string represents a muscle pull; it does not contract itself.

Muscles work in pairsSlide 4 of 11

I Do · learn and modelBUILD · Week 4

The body has a working pair

BEND THE ELBOW	ACTIVELY STRAIGHTEN
Biceps contracts. Triceps relaxes.	Triceps contracts. Biceps relaxes.

Muscles work in pairsSlide 5 of 11

We Do · think togetherBUILD · Week 4

Choose the pulling muscle

The card arm bends.

Choose: biceps or triceps contracts?

Say, sign or point before the explanation.

Muscles work in pairsSlide 6 of 11

We Do · think togetherBUILD · Week 4

Now swap the action

The model actively straightens.

Which muscle contracts now?

What happens to its partner?

Muscles work in pairsSlide 7 of 11

We Do · think togetherBUILD · Week 4

Model and muscle: compare

WHAT THE MODEL SHOWS	WHAT IT DOES NOT SHOW
A joint allows movement. A pull acts on each side. The roles can swap.	String does not shorten itself. Card is not living bone. This is a simplified elbow.

Muscles work in pairsSlide 8 of 11

I Do · learn and modelBUILD · Week 4

Explain both muscle jobs

When the elbow bends, the biceps contracts and the triceps relaxes.

When it actively straightens, the pair swaps jobs.

Muscles work in pairsSlide 9 of 11

We Do · think togetherBUILD · Week 4

True or needs correcting?

READ EACH CLAIM	EXPLAIN THE CORRECTION
Muscles can pull. Muscles can push bones. Biceps and triceps form a pair.	Which claims fit the model? Which word needs changing? Show the action that supports you.

Muscles work in pairsSlide 10 of 11

We Do · think togetherBUILD · Week 4

Direct two moves and keep labels

Direct one bend and one active straighten.

Place CONTRACTS and RELAXES labels.

Check one swap and correct it if needed.

Keep the labels for Wednesday.

Muscles work in pairsSlide 11 of 11

Use the controls or left and right arrow keys. Printing includes pupil content; model answers remain separate.