Muscles work in pairs because a muscle can only pull. One muscle pulls a bone one way and its partner pulls it back, like the biceps and triceps. Put this 3D figure on the board and press a muscle: the view glides in, that muscle lights up and a box says what it does in plain words. Turn the body round for the muscles on the back, then press Pairs to watch the arm bend.
On the front: the deltoid, the pectorals, the biceps, the abdominals, the quadriceps and the tendon below the kneecap, with the heart glowing inside the chest, because the heart is a muscle too. Back turns the body round: the trapezius, the triceps, the gluteus, the hamstrings, the calf and the Achilles tendon.
A muscle can only pull, it cannot push. Pairs turns the body side on and the arm bends at the elbow: the biceps pulls and gets shorter and fatter while the triceps relaxes. Then the arm straightens: the triceps pulls and the biceps relaxes. These are antagonistic muscles, the KS3 words for a pair that pull in opposite directions. Textbooks say the working muscle contracts, where the board says it pulls. Another pair is on the model too: the quadriceps straighten the knee and the hamstrings bend it. Only the arm is shown moving.
No. A muscle can only pull, by getting shorter. It cannot push a bone back, so another muscle on the other side has to pull it back instead. That is the whole reason for pairs. In Pairs, watch the biceps get shorter and fatter as the arm bends, then go thin again while the triceps does the pulling. If the class has made a model arm from card and elastic bands, this is the same thing on a real arm: each band can pull but never push.
More than 600. The model names ten of the main ones near the surface, front and back, plus two tendons and the heart, which is a muscle too. Each has an everyday home. The deltoid caps the shoulder, the pectorals cross the chest, the abdominals run down the tummy, the quadriceps are the front of the thigh and the hamstrings the back, the gluteus is your bottom, and the trapezius spreads across the upper back and neck. There are three kinds of muscle in all: the ones on the model that move your bones, heart muscle, and the smooth muscle in places like your stomach, which the model does not show.
Switch to More detail and the board adds fourteen more labelled muscles for ages 11 and up, and five names change to their proper ones: pectoralis major, rectus abdominis, gluteus maximus, gastrocnemius and the patellar tendon. The extra names include the latissimus dorsi, the widest muscle of the back, the external oblique at the waist, the sartorius, which is the longest muscle in the body, the soleus under the calf and the tibialis anterior beside the shin. Each has its own box in plain words. On Simple, the board shows the main muscles for ages 7 to 11.
Press a name to zoom in and read what that muscle does. Quiz: press Labels once and every name hides behind a question mark until a pupil presses it. Turn the body by dragging. Draw on the board with the pen, and print a pupil sheet with blank labels and a word bank.
The words are pitched at ages 7 to 14: Years 3 to 9 in England, 2nd to 8th grade in the United States. England Year 3, Animals, including humans: identify that humans and some other animals have skeletons and muscles for support, protection and movement. KS3 biology: the function of muscles and examples of antagonistic muscles. In the United States it supports NGSS MS-LS1-3, which names the muscular system.
What do the main muscles do?
The biceps bends your arm at the elbow and the triceps straightens it. The deltoid lifts your arm. The pectorals pull your arms across your chest. The abdominals help you sit up. The quadriceps straighten your knee and the hamstrings bend it. The gluteus pulls your leg backwards and the calf lifts your heel. The trapezius moves your shoulders and helps hold up your head.
Why do muscles work in pairs?
A muscle can only pull, it cannot push. So to move a bone one way and then back again, you need two muscles pulling in opposite directions. When the biceps pulls, the arm bends and the triceps relaxes. When the triceps pulls, the arm straightens and the biceps relaxes. Pairs like this are called antagonistic muscles.
What joins a muscle to a bone?
A tendon: a strong cord at the end of the muscle. When the muscle pulls, the tendon pulls the bone. The model shows the tendon below the kneecap and the Achilles tendon, which joins the calf to the heel. Ligaments are different: they join bone to bone.
Is the heart a muscle?
Yes. The heart is made of its own kind of muscle, found only in the heart. It is called cardiac muscle, and it is involuntary: it works without you choosing. It squeezes over and over to pump blood round the body, all your life, without you thinking about it. The model shows it as a soft glow inside the chest, behind the breastbone and a little to the left.
What age is it for?
Ages 7 to 14: from Year 3, where pupils learn that humans have skeletons and muscles for support, protection and movement, up to KS3, where they learn about antagonistic muscles.
Is it free?
Free to try. Opening Science Simulations uses one token for the whole day, however many times you come back to it. Every account gets 20 free tokens, and Pro gives 50 a day.
Muscles pull on bones, and the interactive human skeleton names them. The heart simulation shows the heart muscle pumping, and the reflex arc simulation shows a message telling the arm muscles to pull. All twelve are on the Science Simulations page. For models the class can spin, from skeletons to dinosaurs, try 3D Explorer.