The Muscular System

Chapter 10

Understanding Muscles

• Pull never push• Attach to skeleton via tendons or muscles via

aponeurosis• Attachment points– Origin: end attaches to a stationary bone; doesn’t

move– Insertion: end attaches to a moving bone; moves

• Contractions shorten muscles

Functional Groups• Agonist (prime movers)– Prime responsibility for causing a movement

• Antagonist– Oppose/reverse movement– Regulate agonist by adding resistance

• Synergist– Assist prime mover– Add extra force or reduce undesirable movement

• Fixators– Immobilize bone or muscle origin

• Not mutually exclusive

Naming Muscles

• Location– Bone or region associated w/– E.g. brachii and femoris

• Shape– E.g. deltoid and trapezius

• Size– E.g. maximus, minimus,

longus• Action – E.g. flexor , extensor,

supinator

• Direction of fibers & fasicles– E.g. rectus, oblique,

transversus• Number of origins– E.g. biceps and triceps

• Location of attachment– Points of origin & insertion– E.g. sternocleidomastoid

Fasicle Arrangement• Determines range of mov’t & power• Types

– Parallel (fusiform)• Parallel to long axis

– Pennate• Short & attach obliquely to an insertion

tendon• Uni-, bi-, or multi

– Convergent• Broad origin converges to an insertion

– Circular• Concentric rings around external openings• Contractions close

Lever Systems• A lever (bones) moves on a fulcrum (joints) when

effort (muscle contraction) moves a load (bone and everything else)

• Mechanical advantage (power lever)– Effort farther from load then fulcrum– Little effort needed– Force gained for speed and stability– E.g. car jack

• Mechanical disadvantage (speed lever)– Effort nearer load then fulcrum– Force lost for speed and range– E.g. shovel

• First– Mechanical advantage or

disadvantage• Second– Uncommon in body– Always mechanical advantage

• Third– Most skeletal muscles– Always mechanical

disadvantage

Classes of Levers

Learning Muscles

• Need to know– Names of major muscles– Basic functions/actions of muscles

• Table 10.1– Location

• Studying– Learn names

• Look for clues in names from existing knowledge• Draw and or act out• Identify on models or self