TBL 1

Question 1

Locomotion

Answer 1

protraction (extensions) and retraction (flexion) of the limbs through joint rotation to propel the body

Question 2

moment

Answer 2

= joint torque

= joint rotation

Question 3

components of a moment

Answer 3

Active muscle forces, passive tendon and ligament stretches, and forces between the limb and ground (‘ground reaction force’)

Question 4

magnitude of the moment

Answer 4

= length of the lever arm (‘moment arm’) + the force acting on it

Question 5

moment arm

Answer 5

the length of the point of application of the force to the center of rotation of the joint

Question 6

musculoskeletal sys

Answer 6

composed of levers that trade force for distance

Question 7

levers

Answer 7

create mechanical advantage for muscle-tendon unit

Question 8

magnitude of the moment about a joint

Answer 8

= the product of the force and perpendicular distance between the pt of application of the force and the joint’s center of rotation (fulcrum)

Moment = Force * Distance

Question 9

motionless

Answer 9

flexor moment = extensor moment

M1)(D1) = (M2)(D2

Question 10

Joint flexion

Answer 10

flexor moment > extensor moment

Question 11

Joint extension

Answer 11

flexor moment < extensor moment

Question 12

Generation of force

Answer 12

• muscle contractions
• ligament stretch by storing elastic energy
• interaction of limb w/ ground exerts force on the limb

Question 13

Lever System

Answer 13

• 3 classic lever sys in musculoskeletal sys
• A lever system is a rigid bar that moves on a fixed point called the fulcrum when a force is applied to it.
• Movement is made possible in the body by lever systems that are formed by our muscles and joints working together.
• When the fulcrum is closer to the load, then less effort is needed to move the load

Question 14

Class 1 Lever System

Answer 14

• the fulcrum is located between the load and the effort

ex. scissors or see-saw
ex. proximal part forelimb (humerus)

Question 15

Class 2 Lever System

Answer 15

• the load is located between the effort and the fulcrum.

ex. wheel barrow, tip toes, push-up
ex. radius/ulna

Question 16

Class 3 Lever System

Answer 16

• the effort is located between the load and the fulcrum.

ex. swinging tennis raqueta/baseball bat, tweezers, lifting objects w/ arm, crane

Question 17

Lever arms to create moments in the body

Answer 17

1. sesamoid bones

2. tuberosities

Question 18

Sesamoid bones

Answer 18

increase the lever arm (moment arm) distance from the center of joint rotation

Question 19

Tuberosities

Answer 19

provide a large moment arm for a muscle-tendon unit

Question 20

Fracture configuration

Answer 20

• provide clues to fracture etiopathogenesis (cause/development pathology) and informs strategies for fracture stabilization
• estimate force that created a fracture

Question 21

Compression

Answer 21

• break in shear along 45º angle of compression

- oblique

Question 22

Tension

Answer 22

• transverse fracture

- strait across radial axis of the bone

Question 23

Bending

Answer 23

• induces tension on the convex side of the bone, and compression on the concave side of the bone, the fracture has a transverse component on the tensile side and an oblique fracture on the compressive side.
• butterfly fragment -compression results in two oblique fractures on the compressed (concave) side of the bone.

Question 24

Torsion

Answer 24

• spiral fracture induced by tension along a shear plane, connected by a longitudinal fracture line.

Question 25

Bone geometry

Answer 25

• plays a large role in bone strength in bending and torsion
• the body strategically places the minimal amount of bone material in mechanically advantageous positions b/c bone is heavy

Question 26

hollow cylinder

Answer 26

• Shape of a bone
• The structure is stronger when bent in any direction.
• The resistance to bending is related to the distance of the material from the bending axis raised to the 4th power