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motor unit

one motor neuron + the muscle fibers it innervates


Whole muscle tension depends on the ____ of the muscle, the ____ of motor unit recruitment, and the size of each motor unit


Muscles performing refined/delicate movements (hands) have _____(quantity) muscle fibers per motor unit


Muscles performing coarse/controlled movements have a ____ number of fibers per unit


type of recruitment that delays/prevents muscle fatigue


1 of 3 stages of a muscle twitch; the period between stimulation/response (travel time)


1 of 3 stages of a muscle twitch; the onset to the peak of contraction; muscles shorten


1 of 3 stages of a muscle twitch; uptake of calcium into the sarcolemma; muscle returns to its original length

trepee effect

contractions stronger later in response to stimuli of same strength; possibly due to increased availability of calcium

depnds on LENGTH of fiber at the ONSET of contraction
the optimal length is the RESTING MUSCLE LENGTH


type of contraction; muscle SHORTENS/lifts/constant tension


the relationship between velocity of muscle shortening and the magnitude of the load


type of contraction; muscle tension developed < than load
cannot do work, as it cannot move the load a distance


ATP is generated ____(#) ways for the muscle contraction
1. Direct phosphorylation Creatine phosphate +ADP = ATP
2. Oxidative phosphorylation = 36 ATP
3. Glycolysis = 2 ATP + lactic acid

muscle fatigue

the physiological inability to contract; when no ATP available for contraction


cycle that uses
lactic acid in glycolysis >(resynthesized)> glucose in liver >> gluconeogenesis (requires 6 ATP to produce 2 ATP) >>undergoes aerobic respiration >> 36 ATP


the inability to detach the crossbridges

central fatigue

when the CNS can no longer activate motor neurons supplying working muscles; psychological; biochemical changes at the synapse

slow oxidatve

aka type I

fast oxdative

aka type II

fast glycolytic

aka type III

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