1. KS 3 Science
Antagonistic muscles

2. How do muscles work? Muscles can only pull.
Muscles are attached to bones by tendons.
Muscles pull when they contract.
Muscles get shorter and fatter when they contract.
Muscles usually work as pairs pulling in opposite directions – these are called antagonistic muscles.

3. The muscles of the upper arm:
Biceps muscle
Triceps muscle

4. Antagonistic muscle action in the human arm:
Press a muscle to make it contract

5. Raising the arm
Biceps contracts
Triceps relaxes

6. Lowering the arm
Triceps contracts
Biceps relaxes

7. More antagonistic muscles – the leg:
What happens if: B
Muscle A contracts? A
- Leg bends at knee.
Muscle B contracts? C
- Leg straightens at knee.
Muscle C contracts?
- Ankle straightens, pointing toes. D
Muscle D contracts?
- Ankle bends.

8. Synovial joint structure
Ligament
Ligament
Synovial membrane
Cartilage
Synovial fluid
Femur (thigh bone)