Bone and Muscles as Body Lever Systems

Flashcards covering key concepts: fulcrum, effort, resistance, and first/second/third-class levers with body examples.

What is the Fulcrum (F) in the body lever system?

The point or line around which the lever moves, provided by a joint.

What does Effort (E) represent in the lever model?

The force required to move the lever; the point at which the muscle inserts on the bone to exert its contractile force.

What is Resistance (R) in the lever model?

The weight the muscular contraction must overcome; usually concentrated in a small area on the lever.

In a first-class lever, where is the fulcrum located?

Between the effort and resistance.

What anatomical structure provides the fulcrum in the common first-class lever example involving the triceps?

The humero-ulnar joint (olecranon process of the ulna).

Name a real-world example of a second-class lever in the body.

Rising on the toes (standing on tiptoes).

In the standing-on-toes example of a second-class lever, where is the effort applied?

At the heel.

In the standing-on-toes second-class lever, where is the fulcrum?

The ball of the foot.

Where is the resistance located in the second-class lever standing on tiptoe?

The body's weight at the summit of the transverse arch.

In a second-class lever, how is the arrangement of fulcrum, resistance, and effort described?

Fulcrum at one end with resistance between fulcrum and effort.

In a third-class lever, where is the fulcrum located?

At or near one end of the lever.

Which lever class is most common in the body?

Third class lever.

Give an example of a third-class lever in the arm.

Biceps brachii tendon inserted on the radial tuberosity; flexing the forearm at the elbow.

In a third-class lever, where is the effort positioned relative to the fulcrum and resistance?

Effort lies between the fulcrum and the resistance.