Skeletal muscle: contraction, tension and fiber types Flashcards
what is actin
a structural scaffold that runs along the myofilament, that forms the thin filament.
what is myosin
acts as a motor molecule, attaching to actin and generating a force to pull, that forms the thick filament
explain the attached state in the cross bridge cycle
Just finished a contraction:
myofilaments has just finishes a power stroke (pulling action)
actin and myosin cross-bridge are still present
explain the released state in the cross bridge cycle
A molecule of ATP binds to the myosin, in preparation for releasing some energy to prime the myosin head.
The binding of ATP causes the myosin head to release actin.
no more cross-bridge.
explain the cocked state in the cross bridge cycle
the myosin head burns the ATP to make energy (and some ADP waste)
it stores the energy by changing the shape of the myosin - getting it ready to pull on actin again
is in a high energy state - waiting
explain the cross-bridged state in the cross bridge cycle
If calcium is present and bound to the myofilament, then its time for the next contraction
Energized myosin head now binds to actin to form a cross bridge
explain the power-stroke state in the cross bridge cycle
There is a cross bridge now with an energized myosin head attached to actin
the myosin uses its stored energy to pull causing the actin to slide
the sarcomere shortens causing a contraction
2 factors that tension/force in muscles depend on
- number of muscle fibres recruited
- the rate at which the muscle is stimulated
definition of recruitment
process of activating more fibres to make more force
tetanus definition
maximal signaling and contraction capability of a muscle, and where the force will plateau
2 types of muscle types
- fast fibres
- slow fibres
