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6.4Unit 7: Nutrition, health and movement

Moving the body — Cambridge Checkpoint Biology 0893 Revision Notes & Topical Questions

5 min read 10 parts Lesson 4 of 4 1 quiz

📚 Cambridge Checkpoint Biology 0893 Hub / Topical Revision
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Lesson summary

6.4 Moving the body — CHECKPOINT BIOLOGY 0893 notes: Describe the skeleton, joints and muscles, and explain how antagonistic muscles move the arm at the elbow.The human skeleton is inside the body and is made of bones.Insects and other arthropods have a skeleton on the outside, w…

  • Hinge joint
  • Ball-and-socket joint
  • Contraction
  • Insects and other arthropods have a skeleton on the outside, which is called an exoskeleton
  • Functions of the skeleton:Support, to give the body shape
  • Protection of organs, for example the skull protects the brain and the ribs protect the heart and lungs

Section 1 of 10The skeleton

1
The human skeleton is inside the body and is made of bones.
2
Insects and other arthropods have a skeleton on the outside, which is called an exoskeleton.
3
Functions of the skeleton:
  • Support, to give the body shape.
  • Protection of organs, for example the skull protects the brain and the ribs protect the heart and lungs.
  • Movement, because muscles are attached to bones.
  • Making blood cells in the bone marrow.
4
Bones are hard and strong because they contain a lot of calcium.
  • Without enough calcium in the diet, bones may not grow properly.
5
Bones contain living cells, so protein is needed in the diet to build strong bones.

Section 2 of 10Joints

Joint
Joint a place where two bones meet, and movement of the skeleton can only take place at joints.
Bones cannot bend.
A hinge joint works like the hinge of a door and lets the bones move back and forth in one direction.
  • Examples are the elbow and the knee.
A ball-and-socket joint lets the bones move in a complete circle.
  • One bone has an end shaped like a ball and the other has a cup (socket) that the ball fits into.
  • Examples are the shoulder and the hip.
A fixed joint, such as in the skull, does not move.
The arm has several joints: the shoulder, elbow, wrist and finger joints.
  • The humerus, radius and ulna are the arm bones.
  • The elbow is a hinge joint and the shoulder is a ball-and-socket joint.

Section 3 of 10Parts of a moving joint

Parts of a moving joint
Cartilage covers the ends of the bones to reduce friction and absorb shock.
Synovial fluid lubricates the joint.
Ligaments hold the bones together.

Section 4 of 10Muscles and tendons

1
Bones and joints cannot move themselves, so muscles move the bones at joints.
2
Muscles are made of specialised cells that can make themselves shorter, which is called contraction.
3
Muscles use energy to contract, and they get it from nutrients, especially glucose, released by respiration.
  • The more the muscles contract, the more glucose they use.
4
A muscle can only pull, and it cannot push.
5
Many muscles are attached to bones by tough cords called tendons.
  • When the muscle contracts, it pulls on the tendon, which pulls on the bone.
  • Tendons are not stretchy.
6
A muscle that is not contracting relaxes.

Section 5 of 10Biceps and triceps

Biceps and triceps
The biceps is the muscle on the front of the upper arm and is attached by two tendons to the scapula.
The other end of the biceps is attached to the radius.
The triceps is the muscle on the back of the upper arm and is attached by three tendons.

Section 6 of 10Bending and straightening the arm

Bending and straightening the arm
To bend the arm, the brain sends an electrical impulse along a neurone to the biceps.
  • The biceps contracts and gets shorter, and the triceps relaxes.
  • The biceps pulls on the tendon, so the radius moves upwards and the elbow bends.
To straighten the arm, the triceps contracts and the biceps relaxes.
  • The triceps pulls on the tendon, so the ulna moves downwards.
A muscle cannot push, so a second muscle is needed to pull the arm straight again.

Section 7 of 10Antagonistic muscles

Antagonistic muscles
Antagonistic muscles two muscles that work as a pair in opposite directions at a joint.
When one contracts, it moves the bones in one direction.
When the other contracts, it moves the bones in the other direction.
The biceps and triceps are an antagonistic pair.

Section 8 of 10The arm as a lever

The arm as a lever
The arm acts like a lever, with the elbow joint as the pivot.
A model arm shows that the force needed to lift a load depends on where the muscle is attached.
  • The further the attachment point is from the joint, the smaller the force needed.
  • Adding more mass needs a larger force.

Section 9 of 10Key terms

TermMeaning
JointA place where two bones meet.
Hinge jointA joint that moves back and forth in one direction.
Ball-and-socket jointA joint that can move in a complete circle.
TendonA tough, non-stretchy cord that attaches a muscle to a bone.
ContractionA muscle making itself shorter.
Antagonistic musclesTwo muscles that work as a pair, moving a joint in opposite directions.
BicepsThe muscle at the front of the upper arm that bends the arm.
TricepsThe muscle at the back of the upper arm that straightens the arm.

Section 10 of 10Exam technique

1
Saying a muscle can push — a muscle can only contract and pull.
2
Saying the biceps and triceps contract together — when one contracts the other relaxes.
3
Saying tendons join bone to bone — tendons join muscle to bone and ligaments join bone to bone.
4
Saying bones contain no living cells — they do, so protein is needed for them.
5
Saying the exoskeleton is inside the body — an exoskeleton is on the outside, as in insects.

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