Myofibrils
Myofibrils are built from what three kinds of proteins
Contractile proteins, regulatory proteins, structural proteins
Z disc
Narrow plate shaped regions of dense protein material separate one sarcomere from the next..
A band
The darker middle part of the sarcomere; extends the entire length of the thick filaments
A band and I band
bands create the striations that can been seen in both myfibrils and in whole skeletal and cardiac muscle fibers
Microfilaments (filaments)
bundles of protein that form myofibril
Troponin
component of thin filament; when calcium ions combine it changes shape. the change move tropomyosin away from myosin binding sites on actin molecules and muscle contraction subsequently begins as myosin bind to actin
tropomyosin
component of thin filament; when skeletal muscle relaxed it covers myosin binding sites on actin molecules, preventing myosin from binding to actin
Contractile proteins
generates force during muscle contraction
I band
lighter, less dense area the contains the rest of the thin filaments but no thick filaments; a z disc passes through the center
thin
made of protein actin; on the actin there is an area known as active sites (will make contact with cross bridges)
thick
made of protein myosin
Actin
main component of the thin filament; each actin has a myosin binding site where myosin head of thick filament binds during muscle contraction
Myosin
main component of thick filaments and functions as a motor protein in all three types of tissue; bind to myosin binding sites on actin molecules of thin filaments during muscle contraction
sarcomeres
myofilaments inside the myofibril do not extend the entire length of a muscle fiber instead they are arranged in compartments
Two contractile proteins
myosin and actin
H zone
narrow region in center of each A band that contains thick filaments but no thin filaments
Regulatory Proteins
proteins that help switch muscle contraction process on and off
2 types
thick and thin
2 types of regulatory proteins
tropomyosin and troponin
M line
Region in the center of H zone that contains protein that hold thick filaments together at center of sarcomere
