PE Chapter 8 Flashcards

Lever Systems Overview

• Levers are simple machines that consist of a rigid beam or rod and a fulcrum or pivot point, allowing for force amplification.
• The human body utilizes lever systems formed by bones and muscles to achieve movement and mechanical advantages.

First-Class Levers

• Characterized by the fulcrum placed between the effort (muscles) and the load (body weight).
• Similar in function to a seesaw or scissors.
• Example: The atlanto-occipital joint where the skull acts as the lever, the joint as the pivot, and neck muscles produce the effort. This allows for neck extension with a small force moving the heavier head.

Second-Class Levers

• Load positioned between the effort and the fulcrum.
• Comparable to a wheelbarrow, where the wheel acts as the pivot.
• Example: Standing on tiptoes; the toes are the pivot, body weight is the load, and calf muscles generate the effort for plantar flexion, effectively lifting the body upwards.

Third-Class Levers

• Effort is located between the load and the pivot.
• Example: Bending the elbow where the elbow joint serves as the pivot, the biceps brachii provides the effort, and the forearm/hand acts as the load.
• This lever type does not amplify force but converts a smaller force into swift movements, facilitating quick and extensive action.

Lever Components in the Body

• Anatomical levers consist of:
  • Lever: Bones act as the levers in the human body.
  • Fulcrum: Joints serve as the pivot points where bones connect.
  • Effort: Force exerted by muscle contraction.
  • Load: The weight or resistance that is moved by the lever system.

FRE 123 Model

• An acronym representing the three critical components of a lever: Fulcrum, Resistance (Load), and Effort.
• Positioning of these elements affects the type of lever system and thus its mechanical advantage or efficiency in movement.