Motor Mechanisms Flashcards
The contraction of skeletal muscles is based on
myosin cross-bridges binding to actin and then flexing
A skeletal muscle deprived of adequate ATP supplies will
enter a state where actin and myosin are unable to separate (a.k.a. rigor mortis)
The calcium ions released into the cytosol during excitation of skeletal muscle bind to
troponin
In a relaxed skeletal muscle, actin is not chemically bound to
myosin
Sustained muscle contraction without relaxation between successive stimuli is called
tetanus
The hydrostatic skeleton of the earthworm allows it to move around in its environment by
using peristaltic contractions of its circular and longitudinal muscles
Chitin is a major component of
the exoskeleton of insects
An endoskeleton is the primary body support for the
cartilaginous fishes, including sharks
Types of Muscle
skeleton, cardiac, smooth; all work in the same way, organization of proteins vary
Actin
- gets pulled
- thinner, light bands
Myosin
- pulls
- thicker, dark bands
Sliding Filaments
- contracts to get shorter
- always pull, never push
- long cells
Sliding Filament Theory
- Neural Signal release ACH
- ACH opens sodium channels
- Sodium rushing in depolarized the cell
- Depolarization causes the SR to release calcium ions
- C binds to the troponin and shifts the shape
- The shifting causes the tropomyosin to shift positions
- The shifting uncovers myosin binding sites on the actin
- Myosin binds to the actin
- Myosin releases ADP and Pi causing a shift in shape of myosin-the power stroke
- ATP binds to myosin causing myosin to detach from actin
- ATP is hydrolyzed into ADP and Pi providing the energy to “cock” the head of myosin
- Myosin reattaches to actin and centimes the cross bridge cycle as long as C and ATP are both present
