In this IBDP Biology post, we will be learning about

• The striated muscle and sacromere structure
• Myofobrils

Striated Muscle Structure 

• Muscles are attached to bones and move them
• Composed of 

Muscle fibres: Bundles of muscle cells

• Muscle fibres are longer than typical cells
• Multinucleated
• Sacrolemma (single plasma membrane) surrounds each muscle fibre
• Sacroplasmic Reticulium: Conveys singal to contract all parts of muscle fibres at once and stores calcium
• Many Mitochondria between myofibrils to provide ATP for contractions

Myofibrils 

Muscle fibres contain many myofibrils. The myobibrils have alternating light and dark bands

Myofibrils are made of:

• Repeating units of light and dark bands
• Z line in the centre of each light area
• Sacromere: 

Functional unit of the myofibril. Part of the myofibril between one Z line and the next

The pattern of light and dark bands in sacromere is due to the arrangement of:

• Thin Actin Filaments
• Thick Myosin Filaments

Myosin Filaments:

• Occupy the centre of the sacromere
• Each myosin fillament forms 

crossbridges with actin fillaments during muscle contraction

Structure of a Sacromere  

• Myosin fibres: Thick with head-like structures
• Actin fibres: Thin
• Both are proteins
• Myosin cannot become shorter because it is one continuous protein
• Actin can slide towards the centre of the sacromere and therefore shortens  

That's all for this blog post!

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References:

• https://www.google.com/url?sa=i&url=https%3A%2F%2Ftraining.seer.cancer.gov%2Fanatomy%2Fmuscular%2Fstructure.html&psig=AOvVaw3KtCguqqpgjn554_QzTE_0&ust=1626450538369000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCJjdxMe25fECFQAAAAAdAAAAABAD
• https://lh4.googleusercontent.com/oJmqZpdr-IejkhGpDLsyN0HeFaGqJ0YXjmn8M48tFn36R-Qw3xowTwVTBSAibv7mTSy7II7IiJw26XiYrIRUwVSaB9IMFElzfETHVjtdLUgu7GpcFPe7E3yf5n7ZqzXW7eEaJMg
• https://www.google.com/url?sa=i&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FMyofibril&psig=AOvVaw14rJh891WxBNuaxbtG-BbP&ust=1626451262468000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCMiIuKC55fECFQAAAAAdAAAAABAU

Drafted by Venetia (Biology)