Chapter 7 - Arthrology - Levers

Question 1

What is a lever system?

Answer 1

Interactions of bones, muscles and joints and how they effect locomotion and posture

Question 2

What are the 4 components of levers?

Answer 2

Lever arm, fulcrum, force, resistance

Question 3

What is the lever arm?

Answer 3

A rigid bar… formed by skeletal components

Question 4

What is a fulcrum?

Answer 4

Occurs at the point of least movement along the lever arm…. located at a joint, called the ‘point of rotation’ or ‘pivot point’

Question 5

What is the force

Answer 5

Applied force supplied by muscle contraction or gravity

Question 6

What is the resistance?

Answer 6

Provided by gravitational pull or inertia of body parts (something you are trying to move)

Question 7

What is a first class lever system?

Answer 7

fulcrum is positioned between the force and resistance.

Question 8

Second class lever system

Answer 8

resistance occupies the middle position

Example: Rising on to your toes

Question 9

Third class lever system

Answer 9

applied force is central

Question 10

Gain mechanical advantage

Answer 10

If force is smaller than the resistance
Second class levers always gain

Question 11

Loses mechanical advantage

Answer 11

If force is larger than the resistance
Third class levers always lose

Question 12

What determines if a first class lever gains or loses mechanical advantage?

Answer 12

Gains: fulcrum is closer to resistance
Loses: fulcrum is closer to force

Question 13

What is the moment arm equation?

Answer 13

F x Df = R x Dr
F is force
R is resistance
Df is distance from force to fulcrum
Dr is distance from resistance to fulcrum

F and R.. same units
Df and Dr… same units