Myofilaments Actin, which constitutes about 25 percent of the protein of myofilaments, is the major component of the thin filaments in muscle (per Encyclopedia Britannica Online). Microfilaments Microfilaments or actin filaments are the thinnest filaments of the cytoskeleton found in the cytoplasm of all eukaryotic cells (per Wikipedia Microfilament).
The sarcomere.
Thick filament.
myofibril
Thick Filaments
The thick filament is composed of the myosin molecule. The thin filament is composed of the actin molecule. Flexing the head of myosin provides the powerstroke.
Sarcomeres are composed of actin (thin filaments) and myosin (thick filaments).
Thick Filaments
Yes...ATP causes myosin to detach from actin. Then, Hydrolysis of ATP, which results in ADP and P, causes conformational change in myosin head to swivel or pivot about its axis and then weakly bind to an actin filament. Once the myosin head binds, a conformational change in the myosin head will cause the P to leave (the ADP is still stuck on). The leaving of the P causes the power stroke or "the pulling of the actin filament/rowing stroke". ADP then leaves and the myosin is now back at its original state.
thick filaments
The thick filament is composed of the myosin molecule. The thin filament is composed of the actin molecule. Flexing the head of myosin provides the powerstroke.
Sarcomeres are composed of actin (thin filaments) and myosin (thick filaments).
The head of the myosin filament "walks along" the actin filament forming cross bridges between the two.
Myosin
myosin
actin and myosin.
Myosin
Contraction:Calcium ion (from sarcoplasmic reticulum) binds to troponin of actin filament.Re-orientation occurs in actin filament allowing it to bind to the myosin filament.Globular head of myosin filament binds to actin filament.Myosin filament splits an ATP molecule and as result it bends causing actin filament (attached to it) to slide over it. When the overlap of actin and myosin filament is maximum, filaments will occupy less space thus muscle is in contracted state.Relaxation:ATP binds to myosin filament and myosin returns to its original position (relaxed state).Sarcoplasmic reticulum re-accumulates the calsium ion by active transport. As the result actin filament is dettached from myosin filament.When the overlap of myofibrils is minimal, muscle will be in relaxed state.
The two filaments involved are myosin and actin. Actin: is the framework and slides over the myosin filament when the muscle is shortened. myosin: is a thick filament Also a sacromere: is made up of the actin and myosin. It is the functional unit of a muscle fibre and extends from z line to z line. A muscle contraction: is many sacromeres shortening ( actin sliding over myosin)
The sliding filament model of contraction involves actin filaments overlapping myosin filaments.
actin and myosin
Myofilaments Two types: actin (thin filament) & myosin (thick filament)