# Sliding Filament Theory

acetocolene and neurotransmitters and muscle movement 

(causes muscle contraction here)


## actin and myosin - the thick and thin filaments

the filaments that do the work

excitation contraciton coupling

myosin connects and pulls

**myosin pulls**

myosin head is where the it binds

it keeps going as long it has requirements met


### Step 1
excitation

it has depolorization of the membrane

### Step 2 
excitation

propocation into a t-tubule
- leads from the muscle fiber(cell) to inside sarcoplasmic reticulum (sr)

sarco is calcium storage for muscles

### Step 3
excitation

releases calcium once the sarco is excited/depolarized


### Step 4
excotation

calcium moves toropomiasin to expose the active sites for contraction to occur



Cross bridge cycle aka contraction (4 steps)

### step 5

myosin head connects to the newly exposed active site 
(actin and myosin automatically bind)


### step 6
stored energy used to pivot to pull 
pulls actin strand/shortens muscle

(aside)(muscle cramps)
muscles stuck in position without energy to release the myosin

### step 7
releses myosin from the active site


### step 8
atp broken down to reset


relaxation
### step 9

neural signal ends