7.2.1Unit 6: Practical Skills in Biology II
The Musculoskeletal System — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 4 parts Lesson 23 of 48 Unit quiz
Section 1 of 4Parts of the System
Skeleton
- Bones form a rigid framework that does not shorten or bend, giving muscles a firm structure to pull on.
Skeletal muscle
- Muscles are effectors stimulated by motor neurones and can only produce force by contracting, never by pushing.
Tendons
- Strong, inelastic connective tissue that joins muscle to bone and transmits the pulling force.
Ligaments
- Tough connective tissue that joins bone to bone, holding joints together and keeping the skeleton intact.
Joints
- Places where bones meet, such as the elbow, which acts as a hinge that moves in one plane.
| Tissue | Joins | Role |
|---|---|---|
| Tendon | Muscle to bone | Transmits force of contraction |
| Ligament | Bone to bone | Stabilises the joint |
Section 2 of 4Antagonistic Action
1
Muscles work in antagonistic pairs, because each can only pull and so one muscle is needed to move a bone back after the other pulls it.
2
To bend the arm, the biceps contracts and acts as the flexor while the triceps relaxes.
3
The contracting biceps pulls on the forearm bone via its tendon, and the forearm rotates around the elbow joint.
4
To straighten the arm, the triceps contracts and acts as the extensor while the biceps relaxes.
5
Relaxing muscle returns to its resting length because the opposing muscle stretches it, making contraction possible again.
Section 3 of 4Key Principles
Key Principles
Effectors
- Muscles carry out the response to nerve impulses sent from the central nervous system.
Incompressible bone
- Only a rigid lever can transmit the force, otherwise the muscle contraction would just bend the limb.
Pairs
- Flexor and extensor muscles are arranged on opposite sides of the joint.
Coordination
- The nervous system controls contraction so that one muscle relaxes as its partner contracts.
Section 4 of 4Exam Checklist & Tips
7.2.1 – Key Points for the Exam
- Antagonistic muscles A pair of muscles that pull in opposite directions at a joint.
- Flexor A muscle that bends a joint when it contracts.
- Extensor A muscle that straightens a joint when it contracts.
- Tendon Connective tissue joining muscle to bone.
- Ligament Connective tissue joining bone to bone.
Common Mistakes
- Saying muscles push bones; they only pull as they contract.
- Swapping tendons and ligaments; tendons join muscle to bone and ligaments join bone to bone.
- Stating that both muscles in a pair contract together to produce movement.
- Calling the triceps a flexor of the elbow; it extends the arm.
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