Skeletal muscle (Edexcel Int. A-level Biology)

This lesson describes the detailed structure of a skeletal muscle fibre and the structural and physiological differences between fast and slow twitch fibres. The engaging PowerPoint and acccompanying resources have been designed to cover points 7.10 (i) & (ii) of the Edexcel International A-level Biology specification.

The start of the lesson uses an identification key to emphasise that skeletal muscle differs from cardiac and smooth muscle due to its voluntary nature. It is important that key terminology is recognised so once myology has been revealed as the study of muscles, key structural terms like myofibril, myofilament and myosin can be introduced. Moving forwards, students will be shown the striated appearance of this muscle so they can recognise that some areas appear dark where both myofilaments are found and others as light as they only contain actin or myosin. A quiz competition is used to introduce the A band, I band and H zone and students then have to use the information given to label a diagram of the myofibril.

This part of the lesson has been specifically planned to prepare the students for the upcoming lesson which describes the contraction of skeletal muscles by the sliding filament mechanism

The rest of the lesson focuses on the structural and physiological differences between fast and slow twitch fibres and the following characteristics are covered:

• Reliance on the aerobic or anaerobic pathways to generate ATP
• Resistance to fatigue
• mitochondrial density
• capillary density
• myoglobin content (and colour)
• fibre diameter
• phosphocreatine content
• glycogen content

A wide variety of tasks are used to cover this content and include knowledge recall and application of knowledge exam-style questions with fully-displayed mark schemes as well as quick quiz competitions to maintain motivation and engagement.