Sarcomere Vocabulary Worksheet
Sarcomere 
Sarcolemma 
Myofibril 
Thin Filament 
Thick Filament 
A band 
I band 
H zone 
Z disc 
M line 
Sarcomere  Basic unit of the striated muscle fiber, contractile unit of a myofibril; sarcomeres are
repeating units, defined by borders of the Z band, along the length of the myofibril.
Sarcolemma  Also called the myolemma. The cell membrane of striated muscle fibers. Contains a
typical plasma bi layer membrane as well as l glycocalyx, a type of polysaccharide, so the muscle has
something to adhere to. Invaginates the muscle fiber to form transverse tubules (T Tubules).
Myofibril  Slender thread of striated muscle fiber.
Thin Filament A type of myofilament. Contains actin, tropomyosin, and troponin.
Actin is a globular protein and can be a single monomer, G actin or twisted together as a polymer, F
actin.
Tropomysoin is a long thread like protein that covers actin’s myosin binding sites.
Toponin a globular protein that coves tropomyosin. Change’s it’s shape when it interacts with Ca++.
Thick Filament  A type of myofilament. Contains myosin. Has a light chain and a heavy chain twisted
together. Contains a head, neck, and tail domain.
A band  Middle area of the sarcomere where both thick and thin filaments are found. Appears darker.
I band Contains thin filaments but no thick filaments. Appears lighter.
H zone  Contains thick filaments but no thin filaments.
M line  Formed from cross connecting elements of the cytoskeleton that holds the H zone in place.
Z disc  Region where thin filaments are inserted. Defines the borders of the sarcomere.