The Muscular System “myo = muscle”

Muscular System There are over 600 skeletal muscles They make up 40-50% of our body weight Muscles play a crucial role in communication No other animal has more complex facial muscles than humans have The smallest muscle in the body is the stapedius and controls the stapes (stirrup bone in the ear) The largest muscle in the body??? Gluteus maximus!

Skeletal Muscle Cells Muscle cells are called muscle fibers Layers of connective tissue group muscles fibers together and give them strength The epimysium, perimysium, and endomysium, are continuous with each other. Perimysium holds muscle cells together to form a fascicle. Fascia is tough connective tissue that covers muscle organ including the epimysium

Levels of Organization of a Muscle Muscle Fascicles Muscle Fibers (cells) Myofibrils Thick/Thin filaments

Shape, Size and Arrangement Skeletal muscles are considered organs Their arrangement and shape are suited to their function Parallel Convergent Pennate Bipennate Sphincter

Origin and Insertion Points During contraction one bones usually stays stationary Skeletal muscles can only contract Origin is point of attachment that doesn’t move Insertion is point that does move with contraction

Muscle Actions Agonist Antagonist Synergist Fixator muscles Also called the prime mover Contracts to produce movement Antagonist Performs opposing action of agonist Relaxes during contraction Synergist Contract at same time of agonist Makes prime movers action more efficient Fixator muscles Stabilize joints Help maintain posture during movement

Lever Systems First class levers Second class levers Work like seesaws Second class levers Work like wheelbarrow Third class levers Flexing of forearm at elbow Most common type in body

Major Muscles of the Body

How Muscles are Named Location Action Direction of fibers Shape Brachialis(arm) & gluteus(buttocks) Action Adductor brevis Direction of fibers Rectus abdominis Shape Deltoid (triangular) Number of heads/divisions Biceps, triceps, quadriceps Origin and Insertion Sternocleidomastoid (sternum, clavicle, mastoid) Relative Size of muscle Gluteus maximus, medius and minimus

Quick Review Connective tissue that covers individual muscle fibers? Endomysium Connective tissue that surrounds and connects fascicles? Perimysium Covers the muscle as a whole? Epimysium or fascia Which term includes all the rest- thin filament, muscle fiber, & myofibril? fascicle This connects muscle to bone. Tendon Name three fiber arrangements? Parallel, convergent, pennate, bipennate, sphincter Point of attachment that does not move with contraction? Origin Does move with attachment? Insertion Muscle that directly performs a movement? Agonist What is the most common type of lever system found in the body? 3rd class Name two ways muscles are named and give examples. Points of insertions-biceps, Shape deltoid, direction of fibers-rectus abdominis, functions-adductor group, location- medialus, lateralis, intermedius