ES - Neuromuscular Anatomy and Phys - Neuromuscular Responses to Exercise Flashcards
Illustrate the activation of muscle contraction (5)
1) AP arrives at nerve terminal from motor neuron causes release of acetylcholine
2) Acetylcholine diffuses across NMJ, causing excitation of sarcolemma
3) Once sufficient Acetylcholine is released, an AP is generated along and activates sarcolemma in muscle fiber.
4) This activation of sarcolemma causes release of Ca from SR within fiber.
5) Ca binds to active site on Actin, opening active site, to allow myosin cross-bridge to bind to active site (MUSCLE CONTRACTION).
How do nerves stimulate muscle activity?
when a motor neuron fires an impulse or AP, all muscle muscles it serves activate and develop force at the same time
All-or-none principle (2)
All muscle fibers in motor unit contract and develop force at the same time, never just some of the fibers.
A stronger AP cannot produce a stronger contraction.
Single Twitch
brief contraction resulting from short activation of muscle fibers when AP travels down motor neuron
Double Twitch
if a second twitch is elicited from motor nerve before fibers completely relax, force from the two twitches summates, resulting in greater force than during a single twitch
AlthoughCa release during a twitch is sufficient to all optimal activation of actin and myosin,…..
Ca is removed before force reaches maximum, and the muscle relaxes.
Tetanus - Decreasing the time intervals between twitches results in…
greater summation of cross-bridge binding forces. The stimuli may be delivered at so high a frequency that the twitch begins to merge and eventually completely fuse. This is the maximal amount of force the motor unit can develop.
Motor unit recruitment patterns
depends on the force/resistance of the exercise.
In large muscles (quads), motor units are activated at near-tetanic frequency when called on.
Increases in force output are achieved through recruitment of additional motor units.
Ways of grading muscular force (2)
1) variation in frequency at which motor units are activated
2) varying number of motor units activated (recruitment)
Motor units recruited per activity (Type I)
100m sprint 800m run marathon olympic weightlifting soccer, lacrosse, hockey american football WR american football LB Basketball, team handball Volleyball baseball, softball pitcher boxing wrestling 50m swim field events cross-country skiing, biathlon tennis downhill or slalom skiing speed skating track cycling distance cycling rowing
depends on the relative involvement of muscle fiber types for each exercise
100m sprint LOW 800m run HIGH marathon HIGH olympic weightlifting LOW soccer, lacrosse, hockey HIGH american football WR LOW american football LB LOW Basketball, team handball LOW Volleyball LOW baseball, softball pitcher LOW boxing HIGH wrestling HIGH 50m swim LOW field events LOW cross-country skiing, biathlon HIGH tennis HIGH downhill or slalom skiing HIGH speed skating HIGH track cycling LOW distance cycling HIGH rowing HIGH
Motor units recruited per activity (Type II)
100m sprint 800m run marathon olympic weightlifting soccer, lacrosse, hockey american football WR american football LB Basketball, team handball Volleyball baseball, softball pitcher boxing wrestling 50m swim field events cross-country skiing, biathlon tennis downhill or slalom skiing speed skating track cycling distance cycling rowing
100m sprint HIGH 800m run HIGH marathon LOW olympic weightlifting HIGH soccer, lacrosse, hockey HIGH american football WR HIGH american football LB HIGH Basketball, team handball HIGH Volleyball HIGH baseball, softball pitcher HIGH boxing HIGH wrestling HIGH 50m swim HIGH field events HIGH cross-country skiing, biathlon LOW tennis HIGH downhill or slalom skiing HIGH speed skating HIGH track cycling HIGH distance cycling LOW rowing HIGH
Neuromuscular adaptations w/ training and locations (???????)
increased rate of force development motor unit synchronization frequency modulation autogenic inhibition reduced antagonist inhibition
