BRAINCAKERelease of Calcium Ions into the Sarcoplasm
The depolarisation of the sarcolemma is spread throughout the muscle fibre by the T-tubles which are in contact with the sarcoplasmic reticulum (SR). The SR actively absorbs calcium ions from the sarcoplasm.
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Key terms in this lesson
- sarcolemma
- The specialised plasma membrane surrounding a muscle fibre.
- sarcoplasm
- The cytoplasm of a muscle fibre, containing large numbers of mitochondria to supply ATP for contraction.
- sarcoplasmic reticulum
- A specialised form of endoplasmic reticulum in muscle fibres that stores and releases calcium ions during contraction.
- actin
- A thin protein myofilament in a myofibril that, together with myosin, slides during muscle contraction; its myosin-binding sites are covered by tropomyosin in resting muscle.
- myosin
- A thick protein myofilament with a hinged globular head that binds to actin and ATP and pulls actin filaments during muscle contraction.