biosci107 07 muscle

description of skeletal muscle

under voluntary control, striated, single long cylindrical cells, multiple peripheral nuclei

description of cardiac muscle

located only in the heart, striated, branched cells with 1-3 central nuclei, connected via intercalated discs, involuntary control

description of smooth muscle

involuntary, found in the wall of internal organs (gut, blood vessels), spindle shaped, uninucleated cells, not striated

structure of skeletal muscle

structure of a sarcomere

T-tubules and sarcoplasma reticulum

the thick filaments

composed of myosin, each myosin has 2 subunits each with a globular head and a tail, the two tails intertwine to form a helix, the heads have a binding site for actin. arranged in a polarised fashion so heads are sticking out in the ends and tails meet in the middle

the thin filaments

composed primarily of globular actin proteins, the filaments are composed of a double stranded helical actin chain (polymers), troponin and tropomyosin are regulatory proteins associated with actin in skeletal and cardiac muscle

sliding filaments theory of muscle contraction

4 major steps of the cross bridge cycle

cross bride formation

the power stroke

detachment

energisation of the myosin head

the importance of calcium in muscle contraction

calcium regulation in skeletal muscle

action potential causes release of Ca²⁺

isometric vs isotonic