Skeletal Muscles & Myofibrils | A-level Biology | OCR, AQA, Edexcel

Skeletal Muscles & Myofibrils in a Snap! Unlock the full A-level Biology course at http://bit.ly/2K24N3p created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University.

SnapRevise is the UK’s leading A-level and GCSE revision & exam preparation resource offering comprehensive video courses created by A* Oxbridge tutors. Our courses are designed around the OCR, AQA, SNAB, Edexcel B, WJEC, CIE and IAL exam boards, concisely covering all the important concepts required by each specification. In addition to all the content videos, our courses include hundreds of exam question videos, where we show you how to tackle questions and walk you through step by step how to score full marks.

Sign up today and together, let’s make A-level Biology a walk in the park!

The key points covered of this video include:

1. General Structure of Skeletal Muscles
2. Ultrastructure of Skeletal Muscles

General Structure of Skeletal Muscles

Skeletal muscles are of bundles called myofibrils, which in turn are made of units called sarcomeres. Sarcomeres in turn are made out of two different proteins: Actin and Myosin.

Ultrastructure of Skeletal Muscles

Myofibrils have a striped appearance under an electron microscope. This is because they have alternating light and dark coloured bands, called I (isotropic-light) and A (anisotropic-dark) bands. The ligher regions, called I bands, are where there are only thin actin filaments. The darker regions, called A bands, are where there are both actin and myosin filaments. At the centre of the A band there is a lighter zone called the H-zone which contains only myosin. At the centre of the I band there is a line called the Z line. The distance between adjacent Z lines makes one repeating unit of a myofibril which is a sarcomere. In summary, we can see that sarcomeres are comprised of several distinct regions.

Summary

Skeletal muscles are made up of millions of fibres called myofibrils
Myofibrils are made of smaller units called sarcomeres
Sarcomeres have a striped appearance under an electron microscope
Sarcomeres also have distinct features, namely the I Band, A Band, H zone and Z line