Functions of Skeletal Muscle

Question 1

Define extensibility.

Answer 1

Ability to be stretched or to increase in length

Question 2

Define elasticity.

Answer 2

The ability to return to the original length after a stretch

Question 3

Define contractility.

Answer 3

The ability to develop tension

Question 4

Define irritability.

Answer 4

The ability to respond to a stimulus

Question 5

What are the properties of tendon/fascia

Answer 5

Viscoelasticity
Non-contractility

Question 6

What is an isometric contraction?

Answer 6

Muscle generates tension but does not change length

Question 7

What is an isotonic contraction?

Answer 7

Muscle shortens moving a load
Same tone

Question 8

What is a lengthening contraction?

Answer 8

External load on the muscle causes the muscle to lengthen during a period of contractile activity

Question 9

What is a whole muscle contraction?

Answer 9

tension produced depends on amount of tension developed by each fibre and number of active fibres in the muscle

Question 10

What is the lever system?

Answer 10

Produces a shortening velocity at end of lever arm that is greater than the muscle shortening velocity

Question 11

What are the 3 types of skeletal muscle fibres?

Answer 11

Slow oxidative (type I)
Fast-oxidative (Type IIa)
Fast-glycolytic fibres (Type IIb)

Question 12

What are the features of Type I fibres?

Answer 12

Red fibers
Thin with large amounts of myoglobin and mitochondria
Low ATPase activity
Slow, maintained and lower intensity contractions

Question 13

What are the features of Type IIa fibres?

Answer 13

White fibers
Thicker with high myoglobin and many mitochondria
High ATPase activity - fast contractions
Both sustained and short-lasting contractions
large amount of glycogen

Question 14

What are the features of type IIb fibres?

Answer 14

White fibres
Few mitochondria
rapid accelerations and short lasting maximal contractions
thick and less myoglobin
High ATPase activity of myosin
Fatigue prone
anaerobic

Question 15

Define recruitment.

Answer 15

Increases in muscle tension that are primarily controlled by increasing number of active motor units in a muscle

Question 16

What is the Size Principle?

Answer 16

Slow oxidative motor units recruited first,
then fast oxidative motor units,
finally fast glycolytic motor units

Question 17

Define the Rate Principle?

Answer 17

Increasing the frequency of action potentials in a muscle fibre will increase the mechanical response up to a level of maximal tetanic tension

Question 18

What is muscle fatigue?

Answer 18

Reduction of: muscle force production
contraction velocity
Prolonged relaxation of motor units between recruitment

Question 19

What is the major cause of muscle fatigue?

Answer 19

Increase of intracellular phosphate due to breakdown of creatine phosphate
Reduction of intracellular calcium release
Inadequate oxygen availability

Question 20

How can endurance be increased?

Answer 20

By doing long duration, low intensity exercise
Number of mitochondria and blood vessels increase
which increases a fibre’s capacity for oxidative ATP production

Question 21

How can strength be increased?

Answer 21

By doing short-duration, high intensity exercise
increases fibre diameter and synthesis of actin and myosin

Question 22

Where is maximum isometric tension?

Answer 22

Tension produced at optimal sarcomere length known as L0