Chapter 11: The Muscular System

1
Chapter 11 The Muscular System
2
Chapter 11 Objectives

• What is the basic terminology used to describe
  muscles?
• How are muscles arranged?
• How do joints take advantage of muscle
  contractions?

3
Muscle attachment sites

• Origin
• Proximal attachment
• Point that does not lead to movement of bone
• Insertion
• Distal attachment
• Point that moves a bone
• Belly--fleshy portion of muscle
• Action--movement that occurs when the muscle
  contracts

4
Biomechanics - Levers

• Effort--the pull on the skeleton (muscle)
• Lever--rigid structure (bone)
• Fulcrum--fixed movement point (joint)

5
Biomechanics - Levers

• Levers can change
• Direction of applied force (effort)
• Distance and speed of movement
• Effective strength of that force

6
Mechanical advantage vs disadvantage

• Mechanical advantagesmaller effort moves a
  heavier load.
• Effort must move a greater distance and be faster
  than the load.
• Mechanical disadvantagea larger effort is used
  to move a lighter load.
• Effort must move more slowly and for a shorter
  distance than the load.

7
First-class Lever

• Rarely occurs
• Can use both mechanical advantage or disadvantage

8
Second-class Lever

• Rarely occurs
• Always produces mechanical advantage

9
Third-class Lever

• Most common
• Always produces mechanical disadvantage
• Favors speed of motion over force

10
Fascicle Arrangement

• Parallel
• Fusiform
• Body
• Circular
• Sphincter
• Triangular
• (convergent)

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Fascicle Arrangement Table 11.1

• Pennate
• Unipennate
• Bipennate
• Multipennate

12
Coordination within muscle joints

• Movements are the result of several muscles
  acting as a group
• Agonist (prime mover) contracts to produce a
  movement
• Antagonist stretches and yields to produce
  movement
• Synergists contract and stabilize intermediate
  joints. Located close to prime movers.
• Fixators stabilize origin of the prime mover