HUB191 L9 Flashcards
The myofilament is primarily composed of actin and
myosin
Actin forms the thin filament, a structural
scaffold that runs along the myofilament
Actin
Myosin forms the thick filament and acts a motor
molecule, attaching to actin and generating force to pull
Actin and myosin bind together when calcium is present,
forming cross-bridges and allowing contraction to occur
ATTACHED STATE
RELEASED STATE
ATP clocks it back
Myosin = hand
Actin = rope
In step 2, the hand is cocked and ready.
In step 3, with calcuim the hand grabs the rope, this is the cross-bridge!
COCKED STATE
The myosin head burns the
ATP to make energy and
some ADP waste. Now being clocked back
CROSS BRIDGE STATE
POWER STROKE STATE
The myosin head releases the Pi (inorganic phosphate).
This causes the myosin head to pivot or “snap back” to its low-energy position.
As it pivots, it pulls the actin filament toward the center of the sarcomere
Skeletal muscle force generation depends on the number of
fibres that contract (recruitment) and the frequency of
stimulation, up to a maximum possible force (tetanus).
Skeletal muscle force generation depends on the number of
fibres that contract (recruitment) and the frequency of
stimulation, up to a maximum possible force (tetanus).
The myofilament proteins actin and myosin bind together when
cellular calcium is high, creating cross-bridges. Myosin then
uses the energy liberated from ATP to pull on the actin filament,
causing a contraction.
The myofilament proteins actin and myosin bind together when
cellular calcium is high, creating cross-bridges. Myosin then
uses the energy liberated from ATP to pull on the actin filament,
causing a contraction.
Muscles rich in fast fibres produce lots of force quickly thanks
to their energy reserves, but they tire out quickly too! Slow
fibres are able to generate a lot of energy even while working,
so they are difficult to fatigue.
