BCS 110 Lecture Notes - Lecture 14: Corticospinal Tract, Upper Motor Neuron, Lower Motor Neuron
12 Mar 2018
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Wrists, hands, fingers, toes direct from primary motor cortex - layer 5 to sc from upper motor neurons - contralateral: corticorubrospinal tract: synapses at red nucleus, and crosses before medulla. Slow fibers - red meat - are capable of sustained contraction due to vascularization. Has blood supply without needing its own energy source - sustained contraction. Individual muscles have a mix of slow and fast fibers. Motor units consist of slow or fast fibers; the motor pool to a given muscle contains both types of motor units. Motor units are either fast or slow: flexor and extensor muscles, skeletal muscles belong to one of two categories. Intrafusal fibers are found within muscle spindles, one of two types of muscle proprioceptors (golgi tendon organs are the other type) - proprioceptive sensors. Tell muscle length: muscle spindles are in parallel with muscle fibers and signal muscle length.
