Biomechanics of Skeletal Muscle

Question 1

Agonist vs. Antagonist

Answer 1

• Agonist are the muscles creating same joint movement

- Antagonist are the muscles opposing joint movement

Question 2

Epimysium vs. Perimysium vs. Endomysium

Answer 2

• Epimysium is the outside covering of a muscle
• Perimysium is the dense connective sheath covering a fascicle
• Endomysium is the very fine sheath covering individual fibers

Question 3

Myosin vs. Actin

Answer 3

Myosin is the thick, dark filament

Actin is the thin, light filament

Question 4

What is the contractile unit of muscle?

Answer 4

Sarcomere

Question 5

Fusiform vs. Pennate muscles

Answer 5

• Fusiform muscles have fibers running parallel to one another and to central tendon
• Pennate muscles possess fibers that approach their central tendon obliquely

Question 6

Do fusiform or pennate muscle produce greater maximal force? Why?

Answer 6

Pennate because their fibers are oriented obliquely the muscle can fit more fibers into given length of muscle
*Space-saving strategy

Question 7

3 Components of the Mechanical Model of Muscle

Answer 7

1) Contractile (CC)
2) Parallel elastic (PEC)
3) Series elastic (SEC)

Question 8

What does the contractile component of the mechanical model of muscle do?

Answer 8

Converts stimulation into force

Question 9

What does the parallel elastic component of the mechanical model of muscle do?

Answer 9

Allows the muscle to be stretched

Question 10

What is the parallel elastic component represented by?

Answer 10

extracellular connective tissues (such as perimysium) and other structural proteins located throughout muscle

Question 11

What does the series elastic component of the mechanical model of muscle do?

Answer 11

Transfers muscle force to bone

Question 12

What is the series elastic component represented by?

Answer 12

tendon and structural protein titin

Question 13

At what point on the passive length-tension curve does muscle begin to generate passive tension?

Answer 13

Critical Length

Question 14

Beyond the critical length how does tension build?

Answer 14

As an exponential function

Question 15

What are the A bands in the sarcomere?

Answer 15

Dark bands caused by presence of thick myosin myofilaments

Question 16

What are the I bands in the sarcomere?

Answer 16

Light bands caused by presence of thin actin myofilaments

Question 17

What are the H bands in the sarcomere?

Answer 17

Region within A band where actin and myosin do not overlap

Question 18

What are the M lines in the sarcomere?

Answer 18

Midregion thickening of thick myosin myofilaments in center of H band

Question 19

What are the Z discs in the sarcomere?

Answer 19

Connecting points between successive sarcomeres…Z discs help anchor thin actin myofilaments

Question 20

Describe the Sliding FilamentTheory

Answer 20

Myosin and actin create cross-bridges and slide past one another to create a power stroke which causes the sarcomere to contract

Question 21

What accounts for most of the force generated when the muscle is shortened?

Answer 21

At shortened lengths, all force generated actively

Question 22

What accounts for most of the force generated when the muscle is stretched beyond its resting length?

Answer 22

Passive tension begins to contribute to total force along with active force

Question 23

What accounts for most of the force generated when the muscle is stretched even farther?

Answer 23

Passive tension accounts for most of total force

Question 24

Does eccentric or concentric have a higher total force? Why?

Answer 24

Eccentric has higher total force because it adds in both active force and passive tension

Question 25

Force ______ as a concentric muscle increases velocity of contraction

Answer 25

decreases

Inverse Relationship

Question 26

Force _____ as eccentric muscle increases velocity of contraction (proportional relationship)

Answer 26

increases

Proportional Relationship

Question 27

What is a motor unit?

Answer 27

Group of muscles innervated by the same motor neuron

Question 28

How many muscle fibers per motor unit?

Answer 28

4 to 2000

Question 29

What does the Henneman Size Principle state?

Answer 29

Smaller neurons generally recruited before larger motor neurons

Question 30

3 Types of muscle fibers

Answer 30

• Type I
• Type IIA
• Type IIX

Question 31

Describe Type I Fibers

Answer 31

Slow twitch, oxidative fibers that are red in appearance due to their high myoglobin content. They are found most prevalent in endurance athletes

Question 32

Describe Type IIA fibers

Answer 32

Intermediate fast-twitch fibers that are oxidative-glycolytic

Question 33

Describe Type IIX fibers

Answer 33

Fast twitch, glycolytic fibers that are white in appearance due to their low myoglobin content. They are found most prevalent in sprinters and jumpers

Question 34

3 Ways muscle attaches to bone

Answer 34

1) Directly
2) Via a tendon
3) Via an aponeurosis