Muscle Tissue

epimysium, perimysium, and endomysium

connective tissue layers of muscle tissue

epimysium

dense irregular CT that encircles entire muscle

perimysium

surrounds groups of muscle fibers/bundles called fascicles; dense irregular CT

endomysium

separates and surrounds individual muscle fibers – thin sheath of areolar CT

skeletal tissue characteristics

vascular

neural (innervated by motor neurons)

multinucleated

muscle fibers cannot divide

transverse tubules

thousands of tiny invaginations of the sarcolemma (plasma membrane of a muscle cell)

sarcoplasmic reticulum

fluid-filled sacs that surround each myofibril, store calcium ions

troponin

component of the thin filament, allows myosin to bind to actin, enabling a muscle contraction, is the binding site for calcium

myofibrils

contractile organelles of skeletal muscle

myofilaments

smaller muscle protein structures within myofibrils

thick and thin filaments directly involved in the contractile process

neuromuscular junction

1. propagation of nerve signal

2. release of acetylcholine

3. binding of acetylcholine

propagation of nerve signal

triggers calcium to move down its concentration gradient into the synaptic knob and bind to the synaptic vessels

release of acetylcholine

when calcium binds to synaptic vesicles, this triggers the release of acetylcholine into synaptic cleft

binding of acetylcholine

acetylcholine diffuses across the synaptic cleft and binds to the receptors in motor end plate —> causes excitation of muscle fiber

isotonic concentration

tension developed by the muscle remains almost constant while the muscle changes its length

concentric

eccentric

types of isotonic contraction

concentric isotonic contraction

when the muscle shortens to produce movement and reduces the angle at a joint

eccentric isotonic contraction

when muscle lengthens to resist movement of a load

isometric contraction

tension generated is not enough to exceed resistance of the object to be moved —> muscle does not change its length

cardiac muscle contraction

remains contracted 10-15 times longer than skeletal muscle tissue

• due to prolonged delivery of calcium into the sarcoplasm from the sarcoplasmic reticulum (SR)

skeletal muscle contraction

needs neural signal to contract

contracts faster than cardiac muscle tissue