Chapter 10 muscular System

Question 1

skeletal muscle attachment sites: origin and insertion

Answer 1

-skeletal muscles cause movements by exerting force on tendons, which pull on bones
*articulatng bones usually do not move equally in response to muscle contraction
-the attachment of a muscles tendon to the proximal, stationary bone is called **the origin **
-the attachment of the muscles distal tendon to the movable bone is called **insertion **
-the action of a muscle is the main movement that occurs during contraction ( examples: flexion nd extension)

Question 2

Lever Systems

Answer 2

• a lever is a rigid structure that can move around a fixed point called a fulcrum (F)
  -in a human musculoskeletal anatomy, a fulcrum is a joint.
• a lever is acted on at two different points by two different forces:
  -the effort,which causes movement and
  -the load or resistance, which opposes movement

Question 3

Lever Systems

Answer 3

• The effort (E) is the force due to muscular contraction
  *** The load (L) is the weight that is moved or some resistance of an object to being moved
  -example of load: the weight of a book to be overcome before you can pick it up **
• motion occurs when the effort applied to the bone at the insertion exceeds the load (E>L)

Question 4

Types of Levers

Answer 4

there are 3 types of levers. the difference is in the relative position of the fulcrum effort and load.
●  First-class levers are uncommon: the fulcrum is between the effort and the load.
●  Second-class levers are uncommon: the load is between the fulcrum and the effort. (These levers develop the most force.)
●  Third-class levers are common: the effort is between
the fulcrum and the load

Question 5

Coordination among Muscles

Answer 5

●  It is common to attribute a specific action at a joint to a single muscle, but remember that muscles do not
work in isolation.
●  Movements usually result from several skeletal
muscles acting as a group. In an opposing muscle pair, one is called the prime mover or agonist, which contracts and is responsible for the action, while the other muscle – the antagonist – is relaxed, stretches, and yields to the effects of the agonist
● Most skeletal muscles are arranged in
opposing (antagonistic) pairs at joints
(Example: flexors vs. extensors).
● Antagonists are usually situated on opposite
sides of the body.

Question 6

Coordination among Muscles

Answer 6

●  To assist the movement of the agonist at a joint, muscles called synergists contract simultaneously with the agonist.
●  Example: Brachioradialis assists biceps brachii in flexing the
elbow joint.
●  Synergistic muscles can also stabilize a joint so that the
agonist is more efficient. These muscles are called fixators.
●  Example: Wrist extensors prevent unwanted flexion of wrist
as the finger flexors make a “power grip” fist.