Functions of Skeletal Muscle Flashcards
Define extensibility.
Ability to be stretched or to increase in length
Define elasticity.
The ability to return to the original length after a stretch
Define contractility.
The ability to develop tension
Define irritability.
The ability to respond to a stimulus
What are the properties of tendon/fascia
Viscoelasticity
Non-contractility
What is an isometric contraction?
Muscle generates tension but does not change length
What is an isotonic contraction?
Muscle shortens moving a load
Same tone
What is a lengthening contraction?
External load on the muscle causes the muscle to lengthen during a period of contractile activity
What is a whole muscle contraction?
tension produced depends on amount of tension developed by each fibre and number of active fibres in the muscle
What is the lever system?
Produces a shortening velocity at end of lever arm that is greater than the muscle shortening velocity
What are the 3 types of skeletal muscle fibres?
Slow oxidative (type I)
Fast-oxidative (Type IIa)
Fast-glycolytic fibres (Type IIb)
What are the features of Type I fibres?
Red fibers
Thin with large amounts of myoglobin and mitochondria
Low ATPase activity
Slow, maintained and lower intensity contractions
What are the features of Type IIa fibres?
White fibers
Thicker with high myoglobin and many mitochondria
High ATPase activity - fast contractions
Both sustained and short-lasting contractions
large amount of glycogen
What are the features of type IIb fibres?
White fibres
Few mitochondria
rapid accelerations and short lasting maximal contractions
thick and less myoglobin
High ATPase activity of myosin
Fatigue prone
anaerobic
Define recruitment.
Increases in muscle tension that are primarily controlled by increasing number of active motor units in a muscle
What is the Size Principle?
Slow oxidative motor units recruited first,
then fast oxidative motor units,
finally fast glycolytic motor units
Define the Rate Principle?
Increasing the frequency of action potentials in a muscle fibre will increase the mechanical response up to a level of maximal tetanic tension
What is muscle fatigue?
Reduction of: muscle force production
contraction velocity
Prolonged relaxation of motor units between recruitment
What is the major cause of muscle fatigue?
Increase of intracellular phosphate due to breakdown of creatine phosphate
Reduction of intracellular calcium release
Inadequate oxygen availability
How can endurance be increased?
By doing long duration, low intensity exercise
Number of mitochondria and blood vessels increase
which increases a fibre’s capacity for oxidative ATP production
How can strength be increased?
By doing short-duration, high intensity exercise
increases fibre diameter and synthesis of actin and myosin
Where is maximum isometric tension?
Tension produced at optimal sarcomere length known as L0
