Structure of skeletal muscles Flashcards
What is the plasma membrane called that encloses the muscle fibres?
Sarcolemma
What is the shared cytoplasm called between muscle fibres?
Sarcoplasm
What are myofibrils?
Long cylindrical organelles made of protein that are specialised for contraction
They make up the muscle fibres
What are the two types of protein filaments that myofibrils make up?
Actin - the thinner filament
-Two strands twisted around each other
Myosin - the thicker filament
-Consists of long rod-shaped fibres with bulbous heads that project to one side
What are light bands?
Areas where the actin and myosin filaments do not overlap
Also known as I bands
What are dark bands?
Presence of thick myosin filaments
Edges are dark because the myosin is overlapped with the actin
Also known as A bands
What is the z-line?
Line found in the centre of each light band
What is a sarcomere?
Distance between two z lines
When the muscle contracts, the sarcomere shortens
What is the h-zone?
Lighter coloured region found in the centre of each dark band
Only myosin filaments are present
When the muscle contracts, the h-zone decreases
