10.4 , Muscles acting with bones form lever systems

What is leverage?

Using a lever to move an object.

What is a lever?

A rigid bar that moves around a fixed point.

What is a fulcrum?

The fixed point around which a lever moves.

What are the parts of a lever system?

Fulcrum: joint

Lever: bone

Effort: muscle contraction

Resistance (load): weight being moved

Where is muscle effort applied to a bone?

At the muscle's insertion point.

What are the two things a lever allows an effort to do?

Move a heavier load.

Move a load farther or faster.

What is a power lever?

A lever where a small effort moves a large load.

What is mechanical advantage?

A small effort moves a large load, but the load moves a shorter distance.

What is a speed lever?

A lever that requires greater effort but moves a load farther and faster.

What is mechanical disadvantage?

A large effort is required to move a smaller load, but the load moves farther and faster.

What determines whether a lever has mechanical advantage or disadvantage?

Effort farther from fulcrum than load = mechanical advantage.

Effort closer to fulcrum than load = mechanical disadvantage.

What determines the three classes of lever systems?

The relative positions of the effort, fulcrum, and load.

What is a first-class lever?

The fulcrum is located between the effort and the load.

Examples: seesaw and scissors.

What is an example of a first-class lever in the body?

Lifting your head off your chest.

What is a second-class lever?

The load is located between the fulcrum and the effort.

Examples: wheelbarrow and standing on your toes.

What mechanical advantage do second-class levers have?

Mechanical advantage; they provide strength but sacrifice speed and range of motion.

What is a third-class lever?

The effort is located between the fulcrum and the load.

Examples: tweezers and forceps.

What is an example of a third-class lever in the body?

The biceps lifting the forearm and anything held in the hand.

What is the advantage of third-class levers?

They allow faster, more extensive movements but require greater effort.