Neuromuscular Junction / Sliding Filament Theory

Step 1:

The brain decides to contract a skeletal muscle

Step 2:

Motor neurons carry the action potential down the spinal cord to the skeletal muscle

Step 3:

The action potential arrives at the neuromuscular junction

Step 4:

The action potential causes the axon terminal to release Ach

Step 5

Ach binds to receptors on the sarcolemma

Step 6

The binding causes the action potential to travel down the sarcolemma

Step 7

The action potential travels down the T-tubules

Step 8

The sarcoplasmic reticulum is stimulated by the action potential and releases Ca2+

Step 9

Ca2+ triggers the muscle fiber to contract

Step 10 (SFT)

(At rest) Myosin head is bound to ATP. It hydrolyzes the ATP

Step 11 (SFT)

The myosin head binds to the actin (cross bridge)

Step 12 (SFT)

The myosin head releases the ADP and phosphate, and the myosin head bends and it performs a power stroke

Step 13 (SFT)

A new ATP molecule binds the myosin head, and lets the myosin head detach

Without ATP

The myosin head would not detach and causes rigor mortis

Why ATP is important

ATP is needed for the myosin to separate from the actin

Actin

Thin filament

Myosin

Thick filaments