Sliding Filament Theory

Step 1

Ach of NMJ → bind to AchR → EEP → AP

Step 2

Action potentials moving c.v. across surface muscle (sarcalemma)

Step 3

Current will continue to spread + will move into transverse tubules (t-tubules) deep regions

Step 4

Modified E.R. = sarcoplasmic reticulum meshwork surrounds all myofibrils and it holds Ca²+

Step 5

t-tubules have a voltage-sensor activated to turn on Ca²+ release channels (Ryanodine Receptors) in S.R.

Step 6

SR dump Ca²+ → bind troponin

Step 7

Tropomyosin slides out of way = A-M crossbridge

Step 8

Calsequestrin pumps Ca²+ back into SR, stopping the contraction

Step 9

With calcium gone, inhibitory state

3 things needed to sustain contraction

1. ATP, Mg²+

2. Ca²+

3. AP (Action Potential)

Sliding Filament Theory

Z lines moving together via A-M crossbridge