NRSC 335 Lecture 18: motor
11 May 2017
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Motor machinery: actions defined by skeleton and muscles, muscles attached to bones by tendons, antagonists/synergists, bones/joints limit range and direction of movement, muscles determine force and rate of movement. Muscle composition: made up of many muscle fibers (10-100 um) Spinal motoneurons: motoneurons send axons to muscle fibers, nmj uses acetylcholine, ach receptors on muscle fiber mediate depolarizing na+ Large, efficient synapse = neuromuscular junction (nmj ) current. E nd p late p otential (e p p : e p p s produce muscle fiber action potentials, muscle ap release c a+ from intracellular stores to initiate actin/myosin cascade. Sensory feedback: movements must be monitored to be performed properly, muscle sense = proprioception, activity of motor centers. 2 types of sensory organs: muscle spindles, g olgi tendon organs. S pindle responds to muscle stretch: g to responds to stretch and contraction. S pinal cord has circuitry for many motor patterns: direct projection (pyramidal tract)
