Muscles

Describe the general role of muscles in the human body.
Explain how muscles contract and work in antagonistic pairs to produce movement at joints.
Describe how muscle strength can be measured using a Newton scale and the unit Newtons (N).

Muscles are found all over your body and have many important jobs:
- They allow you to move your limbs, like your arms and legs, for actions such as walking, running, and writing.
- They help you maintain your posture, whether you're sitting or standing.
- Some muscles work automatically without you thinking about them, like those that help you breathe, move food through your digestive system (gut), and the special muscle that is your heart, which pumps blood around your body.

Muscles work by contracting, which means they get shorter and tighter.
When a muscle contracts, it pulls on a bone it is attached to. This attachment is usually made by a strong, non-elastic cord called a tendon.
If the muscle is connected across a joint, this pulling action causes the joint to move.
A key thing to remember is that muscles can only pull; they cannot actively push.

To allow smooth and controlled movement in different directions (like bending and straightening a limb), muscles usually work in pairs.
These are called antagonistic muscles.
When one muscle in the pair contracts (pulls to create movement), the other muscle relaxes and lengthens.
To move the limb back, the roles reverse.
A classic example is in your upper arm:
- To bend your arm: Your biceps muscle contracts (pulls), and your triceps muscle relaxes.
- To straighten your arm: Your triceps muscle contracts (pulls), and your biceps muscle relaxes.
- This teamwork allows you to control your movements precisely.

Muscles pull on bones to create movement. But how strong are they?
- You can measure muscle strength using a Newton scale.
- The more force a muscle produces, the higher the reading on the scale.
- Force is measured in newtons (N).
Examples of how to measure:
- Triceps: Push down on the scale with the back of your upper arm.
- Biceps: Push upward under a table with the front of your upper arm.
- Forearms: Squeeze the scale with both hands using just your thumbs.
These tests help compare how strong different muscles are and show how muscles work with joints to move the body.

Muscles: Tissues made of cells that contract to create movement.
Contract: When a muscle gets shorter and pulls.
Relax: When a muscle lengthens and returns to its resting position.
Tendon: A strong cord that connects muscle to bone.
Antagonistic muscles: Muscles that work in pairs, where one contracts while the other relaxes to produce opposing movements.
Biceps: A muscle in the upper arm that contracts to bend the elbow.
Triceps: A muscle in the upper arm that contracts to straighten the elbow.
Newton (N): The unit used to measure force, including muscle strength.
Newton scale: A device used to measure force or muscle strength.

Research the three different types of muscle tissue (skeletal, smooth, and cardiac) found in the human body and where each type is located.
Investigate how regular physical exercise affects the strength, size, and endurance of muscles.