STUDY GUIDE-THE MUSCULAR SYSTEM
I. INTRODUCTION
A. The muscular system specifically concerns skeletal muscles and associated
connective tissue that make individual muscle organs.
B. This chapter discusses how skeletal muscles produce movement and describes the
principal skeletal muscles.
II. HOW SKELETAL MUSCLES PRODUCE MOVEMENT
A. Muscle Attachment Sites: Origin and Insertion
1. Skeletal muscles produce movements by exerting force on tendons, which in
turn pull on bones or other structures, such as skin.
2. Most muscles cross at least one joint and are attached to the articulating
bones that form the joint.
3. When such a muscle contracts, it draws one articulating bone toward the
other.
a. The attachment to the stationary bone is the origin.
b. The attachment to the movable bone is the insertion.
4. Tenosynovitis is an inflammation of the tendons, tendon sheaths, and
synovial membranes surrounding certain joints (Clinical Connection).
B. Lever Systems and Leverage
1. Bones serve as levers and joints serve as fulcrums.
2. The lever is acted on by two different forces: resistance (load) and effort.
3. Levers are categorized into three types, according to the position of the
fulcrum, effort, and load
a. first-class (EFL)-the fulcrum is between the effort and the load. An
example is pair of scissors.
b. second-class (FLE)- the load is between the fulcrum and effort. An
example is a wheelbarrow.
c. third-class (FEL)-the effort is between the fulcrum and the load. An
example is a pair of forceps.
4. Leverage, the mechanical advantage gained by a lever, is largely responsible
for a muscle’s strength and range of motion (ROM), i.e., the maximum
ability to move the bones of a joint through an arc.
