S1L7 Muscular Adaptations I Flashcards
What are the properties of Type I muscle fibres?
- slow twitch, slow oxidative
- endurance events
- high oxidative capacity, low glycolytic capcity
- high mito and capillary density
- high myglobin content
What are properties of Type IIa muscle fibres?
- fast twitch, fast oxidative and glycolytic
- middle distance e.g. 400m, 800m
- medium oxidative and glycolytic capacity
- medium mito and capillary density
- medium myoglobin content
What are properties of type IIx muscle fibres?
- fast twitch, fast glycolytic
- sprints
- low oxidative, high glycolytic capacities
- low mito and capillary densities
- low myoglobin content
What is the role of myoglobin?
muscles O2 store. shuttles O2 from cell membrane to the mito.
What is a motor unit and how is it associated with the muscle fibre types?
= a motor neuron and all of the muscle cells it innervates.
* Type IIx asso with skeletal muscle - generate more force more rapidly
* Type IIa asso with fast oxidative motor neurons innervating fast ox fibres. quicker force development
* Type I asso with slow oxidative m.neurons innervating slow ox fibres. - fewer muscle fibres, slower rate of force development
What are the all or nothing and size principles?
All or nothing = when the motor neuron contracts, all fibres it innervates contracts . the no. of motor neurons firing depends on the desired force production
Size principle = as smaller motor units fatigue, we recruit progressively larger motor units
what is the sarcomere and what is myosin made up of?
sarcomere = functional unit of muscle joined in series or parallel.
myosin - S1 globular head, S2 flexible region and tail
How doe fibre type change with endurance training?
- higher % of type I fibres
- fast-to-slow shift
- conversion of some type IIx to type IIa and type I
- stimulation for altered MHC gene expression
How does VEGF change with endurance training?
- increased VEGF mRNA and VEGF protein
- causes increased angiogenesis = blood vessel formation
How does blood vessel formation (angiogenesis) change with endurance training?
- increased capillary no. per fibre - greater increase for Type I
- increased capillary density and increased muscle size - smaller diffusion distances so increased transfer of O2 to muscles
How does mitochondria change with endurance training?
- increased mito aggregates
- increased mito size - increased sites for aerobic resynthesis of ATP, oxidation of glucose etc.
