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
• Direction of fibers &
– Bone or region associated w/ fasicles
– E.g. brachii and femoris
• Shape
– E.g. deltoid and trapezius
• Size
– E.g. maximus, minimus,
longus
• Action
– E.g. flexor , extensor,
supinator
– 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
Classes of Levers
• First
– Mechanical advantage or
disadvantage
• Second
– Uncommon in body
– Always mechanical advantage
• Third
– Most skeletal muscles
– Always mechanical
disadvantage
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