Contraction Cycle & NMJ

1st step contraction cycle

Ca²⁺ binds to troponin, tropomyosin shifts, and the actin active site opens

2nd step contraction cycle

myosin head binds to actin active site (b/c it’s open) 

3rd step contraction cycle

ADP + P₂ are released and energy used for power-stroker; myosin head pivots & pulls on thin filament

4th step contraction cycle

an ATP binds to myosin head, releasing cross bridge

5th step contraction cycle

ATP is hydrolyzed and reconnects the head 

1st step neuromuscular junction

signal sent down the membrane, ions rush through channels, and membrane depolarizes

2nd step neuromuscular junction

vesicles full of ACH fuse and ACH is released to synoptic cleft

3rd step neuromuscular junction

ACH binds to sarcolemma ion channels & cation potential produced when ions enter cell 

4th step neuromuscular junction

depolarization creates rush of Ca²⁺ ions from sarcoplasmic reticulum

5th step neuromuscular junction

Ca²⁺ binds to troponin of thin filaments

6th step neuromuscular junction

contraction cycle starts