Motor_Units.csv

corresponds to all of the muscle fibers innervated by a single alpha-motor neuron

some muscles (such as eye muscles) contain many tiny motor units for fine movement; other muscles (such as leg muscles) contain few large motor units for producing posture and propulsive motion

an individual muscle fiber is generally innervated by one motor neuron; exceptions include during development and in pathological conditions

muscle fibers belonging to a unit are intermingled with muscle fibers belonging to other units

motoneuron activity can be monitored via retrograde activation (stimulation of muscle fiber and then recording motoneuron activity)

result from a single motor neuron action potential; important features are amplitude and time-to-peak

result from a train of motor neuron action potentials; represent fusion of underlying twitch contractions

slow contraction associated with smaller force of contraction

rheobase current and afterhyperpolarization

provides an inverse measure of excitability; involves injection of current until an action potential results (more current necessary implies a lower excitability)

occurs after an action potential; duration is inversely proportional with action potential firing frequency

inverse correlation between rheobase current and afterhyperpolarization

positive correlation between firing frequency and force output

slow; fast fatigue resistant; fast fatiguable

correspond to fast fatiguable units

correspond to fast fatigue resistant units

correspond to slow units

units are recruited in order of increasing force from slow to fast fatiguable

process by which motor unit force is increased by increasing motor unit firing frequency

accounts for 10-15% of motor unit force generation