Types of muscle fibres Flashcards
What are characteristics of muscles involved in slow contractions for long periods of time?
more mitochondria for oxidative phosphorylation and ATP production and to have a higher density of surrounding capillaries.
What criteria do we look at when classifying muscle fibres?
how fast some fibers contract relative to others
how fibers produce ATP.
What are the three main types of skeletal muscle fibre?
Slow, oxidative (type I)
Fast, Oxidative-Glycoytic fibres (Type IIa)
Fast, Glycolytic (Type IIb)
Describe slow oxidative fibres
Have many mitochondria and capillaries
Have small fibre diameter and motor unit size
Have high myoglobin content (red)
Low glycogen content
Fatigue resistant
Low glycolytic enzyme and myosin-ATPase activity
Slow speed of contraction
What is the major ATP source of Type I fibres?
Oxidative phosphorylation
What is the main place slow oxidative fibres are found?
Postural muscles (eg. of back)
Why are type I fibres not useful for powerful, fast movements?
They do not produce high tension
Describe fast oxidative fibres
Have many mitochondria and capillaries
Have intermediate fibre diameter and motor unit size
Have high myoglobin content (red)
Intermediate glycogen content, fatigue resistance, glycolytic enzyme activity
High myosin ATPase activity
Fast speed of contraction
What is the major ATP source of Type IIa fibres?
Oxidative phosphorylation
What is a placefast oxidative fibres are found?
major muscles of legs
Used primarily for movements, such as walking, that require more energy than postural control but less energy than an explosive movement, such as sprinting.
What is another name for type IIa fibers?
Intermediate fibres
Compare Type I to IIa fibres
Type IIa produce ATP more quickly and thus can produce relatively high amounts of tension.
However, FO fibers do not possess significant myoglobin (lighter color than the red SO fibers).
Describe fast glycolytic fibres
Have few mitochondria and capillaries
Have large fibre diameter and motor unit size
Have little myoglobin content (white)
High glycogen content
Low fatigue resistance
high glycolytic enzyme activity
high myosin-ATPase activity
Fast speed of contraction
What is the source of ATP for type IIb fibres?
Anaerobic glycolysis
Where might you find more Type IIb fibres?
Extraocular muscles
