Energy and Fatigue Flashcards
How does ATP provide energy for cross-bridges?
Binds to myosin and causes dissociation with actin, leading to a new cross-bridge cycle.
How does ATP provide energy for relaxation?
Pumps Ca2+ back into the SR to end contractions.
How does fatigue occur?
Why does fatigue occur?
Repeated muscle stimulation.
Prevents a lot of ATP being used up - would cause rigor otherwise (new cross-bridge cycles cannot form).
How does high-intensity exercise cause fatigue?
Increased [K+] - depolarisation.
Increased [lactate] - acidifies proteins.
Increased [ADP] and [Pi] - inhibits cross-bridge cycles (delays myosin detachment).
How does long term exercise cause fatigue?
Decreased [muscle glycogen] and [blood glucose].
Dehydration occurs.
How does the central command fatigue?
The cerebral cortex cannot excite motoneurons.
What are the three types of skeletal muscle fibre types?
Slow oxidative (I) - resists fatigue.
Fast oxidative (IIa) - intermediate resistance to fatigue.
Fast glycolytic (IIb) - fatigues quickly.
Describe fast and slow muscle fibres.
Fast - myosin filaments with high ATPase activity.
Slow - myosin filaments with low ATPase activity.
Describe oxidative muscle fibres.
Increased mitochondria - increased OP.
Increased vascularisation - delivers O2 and nutrients.
Contains myoglobin - increased O2 delivery.
Red fibres.
Small diameters.
Describe glycolytic muscle fibres.
Few mitochondria.
Low blood supply.
Increased glycolytic enzymes and glycogen.
White fibres.
Large diameters.
Describe muscle fibre recruitment.
Increased load –> increased number of active motor units.
Which fibres are activated in which order for recruitment?
I –> IIa –> IIb.
What does neural control of muscle tension depend on?
AP frequency to motor units.
Recruitment of motor units.
What causes a decrease in muscle mass?
Denervation atrophy - destruction of nerves / NMJs.
Disuse atrophy - when the muscle is not used.
What causes hypertrophy?
Exercise.
Aerobic - more oxidative fibres.
Anaerobic - more glycolytic fibres.
