PSL300H1 Lecture : Lecture 22 - The Motor Unit
Document Summary
Motor unit: def"n: a motoneuron & all of muscle fibers it, muscle fibers of a motor unit all contract innervates. together. Project from spinal nerve from ventral root, branches at terminal, each branch contacts dif muscle fibre (many cells fused together: note: striping pattern, a given motoneuron innervates 1 type of muscle. Eye: note: actual neuromuscular junction = end plate = set of synapses much stronger connection btwn axon & muscle fibre. The muscle fibers of a motor unit are all of the same type. 3 broad categories of muscle fibers & of motor. Adequate for postural maintenance, semi- forces that go on & on. Intermediate twitch rise-time: fast oxidative/glycolytic, moderate maximal force, some myoglobin, moderate n# of mitochrondria. Fatigues slowly (over several minutes: fast glycolytic, fast twitch rise-time, large maximal force, & large fiber size. Jump out of seat,lift weight: little or no myoglobin: pale fibers, few mitochondria: glycolytic metabolism.
