BS277 Biology of Muscle.
Fibre types.
Objectives.
After this lecture and associated reading you should be able to;

Discuss the molecular basis of fibre isotype structure and function.

Discuss the relative contributions of genetics and environment to muscle fibre isotype.
Background reading.
Jones, D., Round, J. and de Haan, A. (2004) Skeletal muscle; from molecules to
movement. (Chapters 1-6) Churchill Livingstone.
Martini, F.H. (2009) Fundamentals of Anatomy and Physiology. (8th edition).
Chapter 10. Pearsons; Benjamin Cummings.
Twitch characteristics of different fibre types (Fig. 10.15, Martini).

With the aid of a diagram, describe how the twitch characteristics of different (phasic)
muscles reflect fibre type composition.

Give examples of muscles that exhibit fast, slow and intermediate twitch characteristics
and, for each example, explain the relationship between twitch characteristic and the
role of the muscle.
1.
2.
3.

With the aid of a diagram, explain why a fast muscle requires a higher frequency of
stimulation to develop tetanus tension than a slow muscle.
Differences between fibre types (Table 10.3, Martini).

Explain how the histological, cytological and metabolic differences between fast,
intermediate and slow muscle fibres account for their relative speeds of contraction and
resistance to fatigue.

Describe and explain the relationship between speed of shortening and rate of ATP
cycling (ATPase activity) across muscles from a variety of species.
The molecular basis for fibre isotype differences.

Describe the molecular structure of myosin.

Which parts of the molecule have the following functions?
1. Enzyme (ATPase) activity.
2. Actin binding.
3. Aggregation into heavy myofilaments.
4. Regulation of contraction in smooth muscle.
5. Articulation between myofilament core and the cross bridge neck.

Describe the molecular components of the thin myofilament.

Name the 4 MHC isotypes in humans.

Describe how the three adult MHC isotypes may be distinguished from each other
histologically by preincubation of tissue sections under different conditions.

Outline the relationship between isotypic variation in other myofibrillar proteins and
fibre type.
The identification of muscle fibre types.

Describe how a muscle biopsy may be obtained.

Describe how fibre type distribution in a biopsy may be established on the basis of
1. Enzyme histochemistry.
2. Immunohistochemistry.

Describe the differences in fibre type distribution between elite endurance athletes and
elite power athletes.
Motor units.

Define and describe a motor unit.

How do ‘motor units’ relate to ‘fibre type’?

With the aid of a diagram, describe the relationship between tension and time in a single
twitch and a tetanic contraction for fast slow and intermediate motor units.

With the aid of a diagram describe the relationships between fibre type, contraction
speed, fatigue resistance and motor unit size (fibre number).

Outline the evidence that there is a neural influence on fibre type.

Outline the evidence that factors other than innervation influence fibre type.

(Discuss the relative contributions of genetics and environment to muscle fibre isotype.)