Muscle Fatigue Flashcards
What is the effect of muscle fatigue on shortening velocity?
Shortening velocity decreases
What is muscle fatigue?
The inability to maintain power output, reversible by rest
Which type of muscle fibre fatigues most rapidly?
Type IIb
Which type of muscle fibre will recover must quickly from fatigue?
Type IIb
What are the metabolic changes which occur due to fatigue?
ADP, Pi, magnesium ions and hydrogen ions all increase in concentration
ATP, creatine phosphate and glycogen stores decrease in concentration
What affects do the metabolic changes which occur with fatigue have on a muscle cell?
Decreases rate of calcium release, reuptake and storage by the sarcoplasmic reticulum
Decreases the sensitivity of the thin filament proteins to activation by calcium ions
Directly inhibits the binding and power stroke motion of the myosin cross brodges
How can muscle fatigue lead to persisting muscle soreness and weakness?
Ryanodine receptors on the sarcoplasmic reticulum can become leaky to calcium ions and lead to persistent elevation of cystolic calcium ion concentration which activates proteases that degrade contractile proteins
Loss of excitability of the motor cortex occurs in what type of fatigue?
Central fatigue
What is the most likely cause of central fatigue?
Reflex inputs from metaboreceptors in muscle
What is peripheral fatigue?
A failure of the excitation contraction coupling mechanism, t tubule action potential, SR activation and calcium release
How can external stimulation be used to detect the type of fatigue?
If direct muscle stimulation delivers smaller forces than normal then the fatigue is peripheral
If the stimulation delivers normal forces then the fatigue is central
What is peripheral fatigue caused by?
Build up of ADP, inorganic phosphate and hydrogen ions which impair calcium fluxes and therefore impairs force delivery at cross bridges
Peripheral fatigue is caused by a lack of ATP. T/F?
False - lack of ATP causes muscle rigor
The accumulation of which molecule has been shown to have the greatest effect on ATP breakdown in muscles?
ADP
How does the build up of hydrogen ions contribute to muscle fatigue?
Hydrogen ions compete with calcium ions for troponin binding
