Transcript I. How Skeletal Muscles Produce Movement

I. How Skeletal Muscles
Produce Movement
A. Origin and Insertion
1. Skeletal muscles produce movement
by exerting force on tendons, which in
turn pull on bone or other structures
such as skin
2. Most muscles cross at least one joint
a. Attached to articulating bones
that form the joint
3. When a muscle contracts, it draws
one articulating bone toward the other
a. Attachment to stationary bone
is the origin
1. Usually proximal
b. Attachment to moving bone is
the insertion
1. Usually distal
c. Belly or gaster is the fleshy part
between
1. Usually closer to origin
4. Origins and insertions are named for
the bones involved with
B. Levers and Lever Systems
1. Bones serve as levers, joints serve as
fulcrums
2. The lever is acted upon by two forces
a. Resistance (load) is the weight
of the part being moved
b. Effort is the force of the
contracting muscle
3. Three types of levers
a. 1st class- fulcrum is between
effort and resistance
b. 2nd class- fulcrum at one end,
effort at the other, and the
resistance in the middle
c. 3rd class- fulcrum at one end,
resistance at the other, and effort in
the middle
4. Leverage- the mechanical advantage
gained by a lever, is largely responsible
for a muscle’s strength and range of
motion (ROM)
a. ROM – the maximum ability to
move the bones of a joint through
an arc