Lec 8

• What are the simple body machines mentioned?

  Levers, pulleys, wheel and axle
• What is a lever?

  • A rigid bar
  • Moves around a fulcrum
  • Requires effort to overcome resistance
• What is the term for the force applied to a lever?

  Effort
• What is the effort arm in a lever system?

  The distance from the force line to the fulcrum
• What is the resistance in a lever system?

  Load that opposes the effort
• What does the resistance arm refer to?

  The distance from the load line to the fulcrum
• How can the human body be considered in terms of levers?

  • Bones act as rigid bars
  • Joints serve as fulcrums
  • Muscles provide effort
  • Weight acts as resistance
• What does mechanical advantage (MA) measure?

  The efficiency of a machine
• How is mechanical advantage calculated?

  MA = Effort arm / Resistance arm
• What does MA = 1 indicate?

  Effort arm equals resistance arm
• What does MA > 1 indicate?

  Effort arm is greater than resistance arm
• What does MA < 1 indicate?

  Resistance arm is greater than effort arm
• What are the functions of a lever?

  1. Change direction of motion
  2. Balance forces
  3. Magnify force
  4. Gain speed and range of motion
• What is a first class lever?

  • Fulcrum is between effort and resistance
  • MA can be greater than, less than, or equal to 1

  
• What happens if the fulcrum is closer to the resistance in a first class lever?

  MA is greater than 1
• What happens if the fulcrum is closer to the effort in a first class lever?

  MA is less than 1
• What happens if the fulcrum is in the middle of a first class lever?

  MA equals 1

  
• What are the anatomical examples of first class levers?

  1. Atlanto-occipital joint
  2. Triceps brachii
  3. Non-weight bearing plantar flexion

  
• What is a second class lever?

  • Resistance is between fulcrum and effort
  • MA is always greater than 1

  
• What is the function of a second class lever?

  To magnify force
• What are the anatomical examples of second class levers?

  Masseter muscle, brachioradialis, weight-bearing plantar flexion
• What is a third class lever?

  • Effort is between fulcrum and resistance
  • MA is always less than 1

  
• What is the function of a third class lever?

  To increase speed and range of motion

  
• What are the anatomical examples of third class levers?

  Masseter muscle, biceps brachii, quadriceps

  
• What are the key characteristics of levers in the human body?

  • Bones as rigid bars
  • Joints as fulcrums
  • Muscles as effort
  • Weight as resistance