BIOL 235 - Ch. 11
questions and
answers (with
diagrams)
Origin
attachment of a muscle that remains relatively
fixed during muscular contraction
Insertion
The attachment of a muscle tendon to a moveable
bone or the end opposite the origin
Belly
thicker, middle region of muscle between origin
and insertion
Action
the main movements that occur when a muscle
contracts
Lever
,A rigid structure that is free to move around a
fixed point. bone acts as a lever
Fulcrum
The fixed point around which a lever pivots.
Effort
the force applied to a simple machine that creates
movement
Load/Resistance
the force that opposes movement
Mechanical Advantage or Disadvantage
Determined by the relative distance between the
fulcrum and load and the point at which the effort
is applied.
Advantage: the load is close to the fulcrum and the
effort is far from the fulcrum.
Disadvantage: the load is far from the fulcrum and
the effort is close to the fulcrum.
First Class Lever
The fulcrum is positioned between the effort and
resistance. Can produce a mechanical advantage or
disadvantage.
Ex. head on vertebral column. Posterior neck
muscles are the effort, atlanto-occipital joint is the
fulcrum and the weight of the anterior skull is the
load.
, Second Class Lever
the load is between the fulcrum and the effort. like
a wheelbarrow. Produces the most force, always a
mechanical advantage.
Ex. standing on tip toes. Ball of foot is fulcrum,
load is body weight and effort is contraction of calf
muscle.
Third Class Levers
Effort placed between the resistance and the
fulcrum.
most common in the body. produce a mechanical
disadvantage, but favour speed and range of
motion.
Ex. elbow joint and biceps brachii.
Prime Mover
the muscle in the opposing pair that contracts to
cause an action
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