contraction of muscle skeletal fiber Flashcards
first
electrical impulses travels down the axon of the motor neuron reaching the synaptic knob.
second
this causes voltage gated calcium (ca) ion channels to open.
third
calcium rushes into the synaptic knob.
fourth
this causes acetylcholine (ach) vesicles to release ach into the synaptic cleft by exocytosis.
fifth
ach diffuses across the synaptic cleft.
sixth
ach attaches to ach receptors in the post synaptic membrane.
seventh
ach receptors open.
eighth
sodium ions rush into the receptors and potassium rushes out.
ninth
this voltage change is known as an end plate potential.
tenth
the electrical impulse causes sodium ion channels to open, causing a wave of depolarization.
eleventh
almost simultaneously potassium ion channels open, causing a wave of repolarization.
twenth
the electrical impulse travels down a transverse tubule.
thirteenth
the electrical impulse is transferred to the terminal cisternae of the sarcoplasmic reticulum.
fourteenth
this causes voltage gated calcium channel ions to open.
fifteenth
calcium rushes into the sarcoplasm.
sixteenth
calcium binds to troponin on the thin filament.
seventeenth
this causes tropomyosin to shift revealing active sites on the thin filament.
eighteenth
the thin filament is prepared to contract, in reality the thick filament is already prepared and the muscle contracts immediately.
first in thick filament
ATP binds to a myosin head.
second
myosin atpase splits ATP into ADP and a phosphate.
third
energy is released into the myosin head causing it to extend into a high energy position.
fourth
the myosin head binds to an active site on the thin filament.
fifth
the ADP and phosphate are released from the myosin head.
sixth
the myosin head flexes into a low energy position while attached to the thin filament.
seventh
this is called power stroke.
eight
the myosin head releases from the active site of the thin filament when a new ATP attached to the myosin head.
ninth
as a result, the sarcomere shortens, myofibers shorten, muscle fibers shorten, fascicles shorten, and the muscle contracts.
