Muscular System

Functions

• Voluntary movement
  
• Forms some sphincters
  
• Protection of some organs
  
• Stabilization of some joints
  
• Posture
  
• Heat production

Organs

• Muscles (includes tendons and aponeuroses)

• Structure of Skeletal Muscles

• Muscle fibers (contractile units within: sarcomeres,  linked end-to end to form myofibrils)
  
• Muscle fibers bundled into fascicles 
  
• Fascicles bundled to form the muscle
  

Connective Tissue in Muscle

• Endomysium
  
• Perimysium
  
• Epimysium
  

How Muscles Create Movement at Joints

• Muscles must cross joints
  
• Insertion pulled towards origin

Fascicle Organization 

• Parallel: greatest range of motion
  

• Convergent: greatest versatility
  

• Pennate: strongest force of contraction
  

• Circular: open and close a hole or passageway  
  

Muscle-Bone Lever Systems

• Most common in body: third class levers (amply movement at the expense of force)
  

Muscle Interaction

• Prime mover: muscle most responsible for an action

e.g.: abduction of arm: deltoid

• Synergistic muscles: assists prime mover

e.g.: supraspinatus assists deltoid in abduction

• Fixators: hold bone of origin steady

e.g.: serratus anterior and rhomboids hold deltoid’s bone of origin steady during abduction

• Antagonistic muscles: action opposite that of the prime mover; must not contract during abduction

e.g.: lats and pects adduct arm