Give us a smile! Are you using more or fewer muscles than it takes to frown?

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Happy Abby, sad Abby! But which requires fewer muscles? Image: science made simple (All Rights Reserved)

by Zoë Gamble

Is it true that you use more muscles to frown than smile?

Actually, there isn’t any proof behind this old saying. Scientists have studied the muscles needed for both facial expressions, and to do a small smile generally uses 10 muscles; a small frown uses 6.   On average, a smile uses 12 and a frown 11. However, since humans tend to smile a lot, these muscles are stronger. A frown may be slightly more effort to produce. just because we aren’t as used to using these muscles.

Don’t move! Are you using any muscles if your body is still?

Yes, in fact you are using many muscles right now. For example, your back and neck muscles are working if you are sitting up, your intercostal muscles (between your ribs) are working if you are breathing, muscles which control eye movement are working so you can read this, and your heart is beating away by itself without you having to think about it.

We have 3 different types of muscles within our bodies, which are specialised for different roles.

Types of muscles

Skeletal muscle

This is, as the name suggests, the type of muscle used to move our skeletons. Muscle tissue is attached to bones by strong tendons, and we contract this muscle to move. We can decide to move these muscles or not, so we say they are controlled voluntarily. We use skeletal muscles to maintain our posture, and hold our bones in place. Skeletal muscle is striated muscle, meaning it has repeated sarcomeres (the basic unit of a muscle) bound by a sarcolemma (muscle cell membrane).

Cardiac muscle

The type of muscle which makes up our hearts is called cardiac muscle. This is controlled involuntarily, and is striated.

Smooth muscle

This is the type of muscle found within our body that is controlled involuntarily, and is not striated (not arranged into repeating sarcomeres) For example, in the digestive tract, blood vessels, and bladder, muscles are working without us putting thought in. Smooth muscle typically has more elasticity than skeletal muscle, and can be stretched further whilst still allowing contraction.

Voluntary or Involuntary?

Although we can control voluntary muscles, sometimes they are outside our control. One example of this is in reflex movements. When babies are born, they have several reflexes which are outside their control. One of these is the ‘grasp reflex’. If you stroke a baby’s palm (under 6 months old), they will close their fingers in a strong grip. Their muscles contract so strongly that it is possible for them to support their own body weight. I’m not recommending that you go and hang the first baby you see on a washing line – they might let go unexpectedly! – but it is possible for them to hold their own weight thanks to the grasp reflex. Another involuntary movement using voluntary muscles is a twitch, and this leads on nicely to….

Fast twitch, slow twitch

Skeletal muscle has fast twitch and slow twitch fibres. Fast twitch fibres contract quickly, but they also tire quickly. Slow twitch fibres contract slower, but will keep on working over a longer period. Thinking back to the Winter Olympics – different athletes bodies are adapted depending on what their event is. A downhill skiier will tend to have more fast twitch fibres, whereas a long distance skiier will tend to have more slow twitch fibres. Find out more about how these athletes use energy here: Winter Olympics! Get some energy! 

Antagonistic Muscles

Antagonistic muscles are skeletal striated muscles. They work as a pair to provide movement.

Antagonistic muscles

Antagonistic muscles control flexing and extension at the elbow. Image: science made simple CC-BY-NC

One pair of antagonistic muscles is in our forearms: biceps and triceps

Muscles work by contracting. When our bicep muscle contracts, this pulls on a tendon connected to the bone in the forearm, flexing (bending) the arm at the elbow. To return the arm to its original position, the triceps muscle contracts, pulling the forearm downwards (extends arm at elbow).

Another example of antagonistic muscles is your quadriceps and hamstrings, used together to move your lower leg. See how they control movement in this animation.

Did you know that..?

  • Our hearts beat approximately 40 million times a year
  • There are about 642 skeletal muscles in the human body
  • Your tongue is the only muscle attached at just one end
  • The heaviest weight ever lifted by a human was 6270 pounds, which was achieved by Paul Anderson in 1957

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KS3 Curriculum links – Muscles

  • The structure and functions of the human skeleton, to include support, protection, movement and making blood cells
  • biomechanics – the interaction between skeleton and muscles, including the measurement of force exerted by different muscles
  • the function of muscles and examples of antagonistic muscles

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Posted in Biology