flexors and extensors that act on the same joint to produce opposite actions
epimysium
the fibrous connective tissue proteins w/in the tendons extended around the muscle in an irregular attangements forming a sheath
fascicles
connective tissue from this outer sheath extends into the body of the muscle, subdividing it into columns
perimysium
each of these fascicles is thus surrounded by its on connective tissue sheath
sarcolemma
each myofibers is surrounded by a plasma membrane enveloped by a thin connective tissue layer called an endomysium
A bands
dark bands
I bands
light bands
Z lines
In an electron microscope a thin dark lines can be seen in the middle of the I bands
motor end plate
the specialized region of the sarcolemma of the muscle fiber at the neuromuscular junction
Acetylcholine (ACh) released by the axon terminals diffuses across the synaptic cleft and bind to ACh receptors in the plasma of the end plate, thereby stimulating the muscle fiber.
motor unit
each somatic motor neuron together with all of the muscle fibers that it innervates
recruitment
when contractions of greater strength are required, larger and larger motor units are activated
myofilaments
smaller structures contained in each myofibril
thick filament (A band)
are primarily composed of the protein myosin
Thin filaments (I band)
are primarily composed of the protein actin
H band
the central lighter regions of the A bands contain only thick filaments
sarcomers
the stuctural subunit of the myofibril in the striated muscle: equal to the distance between two successive Z lines
cross bridges
sliding of the filaments is produced by the actions of numerous cross bridges that extend out from the myosin toward the actin.