Download IN CLASS NOTES = STEPS OF A MUSCLE CONTRACTION

IN CLASS NOTES = STEPS OF
A MUSCLE CONTRACTION
STEP 1
•Calcium ions present
•Ca+ binds to troponin which makes
tropomyosin move out of way for myosin
head to attach
STEP 2
•Cross-bridge attaches.
•ATP breakdown provides energy to ready the
myosin head for a power stroke
•Myosin head attaches to exposed binding site on
actin and the power stroke is accomplished
STEP 3
Cross-bridge (myosin head) springs
from raised position and pulls on the
actin filament.
STEP 4
• Cross bridges break
ATP binds to cross-bridge (but is not yet broken
down)
Myosin heads are released from actin
STEP 5
As long as calcium ions and ATP are
present, this walking continues until
the muscle fiber is fully contracted