Muscle function and levers

Question 1

Contracting and lengthening create ________ of muscles.

Answer 1

actions

Question 2

Agonist

Answer 2

Prime mover, principle mover in producing a given motion at a particular joint.

Question 3

Antagonist

Answer 3

Muscles provide opposite action of agonist.

May be passive/inactive during activity, may change in length while agonist causes movement.

Question 4

Stabilizer

Answer 4

Contracts to stabilize/fixate area to allow another limb/segment to exert force and move.
AKA fixators.

Question 5

Synergists

Answer 5

AKA neutralizer.
Contracts with agonist during motion.
May co-contract identically.
May prevent unwanted actions of agonist.
May stabilize other joints during movement.

Question 6

Parallel muscles

Answer 6

Fibers arranges parallel to length of muscle.

Produce greater ROM than smaller muscles with pennate arrangement.

Question 7

Types of parallel muscles

Answer 7

Fusiform - tendons, big in the middle (biceps brachii)
Flat
Circular - in eyes
Stap - errector spinnate
Radiate/triangular - comes to tendon at a triangle.

Question 8

Pennate muscles

Answer 8

Have shorter fibers, arranged obliquely to their tendons (similar to a feather) so that it increases the cross-sectional area of a muscle to increase power.

Question 9

Types of pennate muscles

Answer 9

Unipennate - thumb
Bipennate - rectus femoris
Multipennate - trapezius, deltoid

Question 10

Type 1 muscle fibers

Answer 10

Postural muscles.
Dark appearance because of concentration of myoglobin and mitochondria.
Smaller in diameter, fatigue slower.
Slow twitch, tonic, or slow oxidative.
Fibers depend on aerobic metabolism.

Question 11

Type 2 muscle fibers

Answer 11

Rapid brief motion.
White.
Large diameter and fatigue quickly.
Fast twitch, phasic, fast oxidative.
Associated with anaerobic metabolism.

Question 12

Properties of skeletal tissue

Answer 12

Extensibility/stretch: ability of a tissue to become longer without injury or damage.
Contractibility: ability of a tissue to shorten.
Tensile strength: ability of a tissue to withstand a pulling force.
Elasticity: ability of a tissue to return to its normal length after being stretched (visco-elasticity).
Creep: gradual change in the shape of a tissue can be permanent or temporary.

Question 13

Isometric contraction

Answer 13

AKA static contractions.
No macroscopic change in length of muscle - doesn’t change in length.
Significant amount of tension may be developed in the muscle to maintain joint angle in a relatively static of stable position.
Occurs to hold a body part in a specific position or to hold a body part in position against a force other than gravity.

Question 14

Isotonic contraction

Answer 14

AKA dynamic contraction.
Involves muscle developing tension to either cause or control joint movement.
Varying degrees of tension in muscle cause joint angles to change.
Either concentric or eccentric based on whether shortening or lengthening occurs.

Question 15

Concentric contraction

Answer 15

Shortening contractions in which tension develops as the insertion of the muscle moves toward the origin enabling movement.
The force developed by the muscle is greater than the resistance.
The joint angle is changing in the direction of applied muscle force.

Question 16

Eccentric contraction

Answer 16

Muscle lengthened under tension with the insertion moving away from the origin resisting or lowering the resistance against gravity.
Controls the movement with gravity.
Force developed by the muscle is less than the resistance, and less energy is expended.

Question 17

Isokinetic contraction

Answer 17

Development of muscle tension through a range of motion at a specific speed - the movement as a fixed speed ensured tension development throughout the motion.

Question 18

Factors affecting muscle function

Answer 18

Types of muscle fibers.
Muscle architecture.
Length of movement.
Fiber arrangement.
Type of contraction.
Length-tension relationship.
Active insufficiency.
Number of joints crossed by muscle.

Question 19

Lever

Answer 19

Rigid bar that turns about an axis of rotation or a function.
Rotate about an axis as a result of force/effort being applied to cause its movement against resistance or weight.

Question 20

Axis

Answer 20

point of rotation about which a level moves.

Question 21

The leverage of a muscle is a major ________ ________ of strength.

Answer 21

Extrinsic factor

Question 22

Lever components

Answer 22

Axis: fulcrum, point of rotation (joint).
Effort or Force: point of force application (insertion).
Resistance: center of gravity of lever or location of an external resistance.

Question 23

First class lever

Answer 23

Axis is between force and resistance.
Produce balanced movements.
Produce speed and ROM when the axis is close to the force.
Produce force motion when the axis is close to the resistance.
Ex: head balanced on the neck in flexion and extension.
See-saw

Question 24

Second class lever

Answer 24

Resistance between axis and force.
Produces forceful movements.
Large resistance can be moved by a relatively small amount of force.
Ex: plantar flexor musculature - raising body op on toes.
Wheel-barrow

Question 25

What is the mechanical advantage of a second class lever?

Answer 25

Less force production can be used to lift entire body weight.

Question 26

Third class lever

Answer 26

Force between axis and resistance. Produce speed and ROM movements. Most common in the body. Requires a great deal of force to move even a small resistance. Ex: brachialis during a bicep curl - it loses leverage for strength of contraction, gains the ability to quickly move the arm through the ROM. Shovel

Question 27

What class lever is an empty hand doing a bicep curl?

Answer 27

2nd class

Question 28

What class lever as a hand with a weight in it doing a bicep curl?

Answer 28

3rd class

Question 29

Force arm

Answer 29

Distance between the location of force application and the axis. AKA torque arm or moment arm.

Question 30

The greater the distance of the force arm, the ______ torque produced by the force.

Answer 30

more

Question 31

The longer the force arm, the _______ force required to move the lever if the resistance and resistance arm remain constant.

Answer 31

less

Question 32

Resistant arm

Answer 32

Distance between the axis and the point of resistance application.

Question 33

Shortening the resistance arm allows for ______ resistance to be moved if force and force arm remain constant.

Answer 33

greater

Question 34

Muscles with good leverage have greater....

Answer 34

extrinsic strength

Question 35

Muscles with poor leverage have better...

Answer 35

speed of movement

Question 36

Angle of pull

Answer 36

Approach to muscle attachment site. Effective strength of a muscle to move a body part at a joint is based on its ability to move the bone in the direction of motion that is to occur.

Question 37

What is the optimum angle of pull?

Answer 37

Perpendicular to the long axis of the bone

Question 38

Passive insufficiency

Answer 38

Movement on one side of a joint is limited by the passive tension of a muscle on the other side of the joint to permit full mobility. Ex ankle dorsiflexion - straight vs. bent knee

Question 39

Active insufficiency

Answer 39

Decrease in the muscle torque, produced when full range of motion is attempted in multi-joint muscles. Ex: loss of grip strength as wrist is flexed.