2.  Movements – - voluntary – intend to make; ex. walking - involuntary – you do not control; ex. breathing

3.  Skeletal – - voluntary movement; attached to bone - made of protein fibers – actin and myosin - work together to allow muscle to contract and relax - myofibrils – makes light & dark bands in muscle = striations

4.  Smooth – - not voluntary; found in internal organs - no striations

5.  Cardiac – - not voluntary; found only in heart - striated; complex

6.  Actin & myosin not connected when muscle is relaxed  When contracts, myosin attaches to actin, forming a bridge  Bridge pulls actin, muscle shortens (contracts)  Cells use ATP to break and rebuild bridges

7.  No oxygen, no ATP, no relaxing muscles  Rigor mortis = process when muscles stiffen  Begins ~ 2 hours after death  Begins in small muscles in face  Takes ~ 12 hours for whole body  Can last 24-48 hours  Eases w/ decaying body