Chapter 4 - Peripheral Factors in Neuromuscular Fatigue Flashcards
Discuss the factors that influence actomyosin binding states?
Metabolite changes slow down the contractile speed, influences the number of cross bridges in the high-force configuration of the given time, and/or may influence the force generating capability of individual cross bridges.
What is neuromuscular transmission failure?
Failure of a nervous impulse to be translated into a impulse on the sarcolemma immediately beneath the motorneuron terminal.
Considering the current research what are the three main possibilities behind neuromuscular transmission failure?
The three main possibilities behind neuromuscular transmission failure are neurotransmitter depletion, postsynaptic membrane failure, and failure to propagate the action potential into axon branches (branch block failure).
Define “muscle wisdom”.
The gradual decline in muscle activation during fatigue exemplified by the decrease in the firing frequency of motor units during rhythmic or sustained effort.
What is “Fatigue Reflex”?
How motoneuron cell body knows what is happening at the muscle level.
Information is transmitted via afferents from the fatigued muscle to the spinal cord on that has an inhibitory effect on motorneuron excitability.
What involvement do muscle spindles and golgi tendon organs play in the fatigue response?
Studies show an increase in muscle spindles as fatigue progressed and afferent firing rates did not decrease as much as force did. Golgi tendon organs didn’t change with fatigue and were always related to the force production.
What role, if any, does spinal cord inhibition have on fatigue?
Filtered info during contraction maintains optimal excitation and reduces efficiency.
Compare and contrast excitation of group III and IV afferents.
Group III afferents respond mainly to mechanical stimuli, while group IV afferents are primarily nociceptors but also include mechanoreceptors.
Both group IV and group III afferents exert an inhibitory influence on motorneurons innervating the muscle of origin of the afferents and their synergists.
Explain the current hypothesis for gamma-motoneuron responses.
The current hypothesis for gamma-motorneuron responses is that this mechanism is a compensatory attempt to optimize the firing rates of the spindle afferents at a time when spindle support is declining during fatigue.
What is known about fatigue-related changes in intrinsic motoneuron properties?
Stimulation of group III and group IV afferents results in changes in intrinsic motorneuron membrane properties that would change their firing behavior during excitation.
The changes does not contribute to adaptation during fatigue, instead, the changes indicate a general change in parameters that are significant in cell excitability and rhythmic firing properties.
