Structure and Function
Skeletal – made up of 1000’s of fibres.
Fibres bound together by connective tissue
Each fibre contains:
Numerous myofibrils
Network of tubes called sarcoplasmic
• Many nuclei
Key Terms
• Look at p.33 – copy key terms + fig 3.3
• Understand striated appearance by defining
(and possibly labelling):
• A bands
• I bands
• H zone
• Z line
• Sarcomere
The sliding filament theory
• What you need to know:
Each stage of the process –
Like a ‘comic strip timeline
Can we do this together???????
Different Types of Muscle Fibres
• Two major types – Slow Twitch (ST) Fast
Twitch (FT)
• What you need to know:
• The differences between the 2….
• Complete the table on p.37
Different Types of FT Fibre
• What you need to know:
• Type Iia (FOG) – fast contraction, large force,
fatigues easily
• Type iib (FG) – very fast contractions, very
large forces, fatigues very easily
• What sports use both?
Motor Units and Spatial Summation
Motor unit – a motor neurone and its muscle fibres
All or nothing law – muscle fibres either contract or
do not contract – no such things as a partial
Spatial Summation Although the response of a motor unit is all or
nothing, the strength of the response of the entire
muscle is determined by the number of motor units
activated, and the size of the units involved.
Spatial Summation
• In order to achieve a greater force of
contraction, the brain recruits / tells more and
/ or bigger motor units.
• Basically, SS is described as ‘the brain altering
the number of motor units involved in a
Exam Questions
• When taking a penalty, performers will rely on
their muscles to produce maximal contractions.
What are the characteristics of the type of muscle
fibres used to produce the maximal contractions?
(6 marks)
• Weightlifting is a sport where the performer
generates maximal strength contractions. Explain
what you understand by the term motor unit and
describe how motor units can be used to produce
muscle contractions of varying strength. (5

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