Muscle and Motility: notes and practice questions
- This topic covers the mechanisms of muscle contraction, motility, and adaptations for movement in organisms.
- Muscle contraction is explained by the sliding filament model, involving actin and myosin filaments.
- Muscle relaxation involves the protein titin and antagonistic muscle action.
- Motor units consist of a motor neuron, muscle fibres, and neuromuscular junctions.
- Skeletons provide anchorage for muscles and act as levers.
- Synovial joints facilitate movement through components like bones, cartilage, synovial fluid, and ligaments.
- Locomotion is driven by needs such as foraging, escaping danger, and mate searching.
- Adaptations for swimming in marine mammals include streamlining and flippers.
- Skills include comparing joint range of motion using computer analysis or goniometers.
How it is examined
Sarcomere banding under contraction is a classic HL item: which bands shorten, which stay the same. The mark scheme expects "the A band stays the same length" as a separate mark from "the I band and H zone shorten". Labelled sarcomere diagrams show up in Paper 1A and Paper 1B.
There is no SL content in B3.3. The whole subtopic is HL.
Do not set this topic for SL students.
Guiding questions
- How do muscles contract and cause movement?
- What are the benefits to animals of having muscle tissue?
Linking questions
- What are the advantages and disadvantages of dispersal of offspring from their parents?
- In what ways does locomotion contribute to evolution within living organisms?
Practice questions
2 questions · 2 mediumQuestion 1
MediumPaper 1B · calculator5 marksA sports physiotherapist is assessing the recovery of a patient's knee joint after surgery.
Describe how a goniometer is used to measure the range of motion of the knee.
Outline how computer analysis of images can be used to measure the range of motion of the knee joint.
Think about the parts of a goniometer (the central fulcrum and the two arms) and how they must be aligned with the patient's leg to measure an angle accurately.
Consider how motion capture technology works in sports science, using cameras and software to track specific points on the body as it moves.
Question 2
MediumPaper 2 · calculator5 marksThe blue whale (Balaenoptera musculus) is a marine mammal capable of migrating thousands of kilometers across oceans.
Describe the structural adaptations that enable marine mammals, such as the blue whale, to swim efficiently.
Think about the shape of the animal, its limbs, its skin, and how it generates thrust and maintains stability in the water.
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Where marks are lost
- Command terms are consistently under-read. Students answer describe when the question said explain, so they give an account with no reasons and cap at half marks. The reverse also happens on outline, where a student writes an essay for a 2-mark summary and runs out of time.
