SPHR 2106 Lecture Notes - Lecture 13: Convolution, Cerebellar Vermis, Withdrawal Reflex
12 Mar 2017
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Corticospinal tract neurons come down and synapse with spinal motor nerves out of ventral horn to innervate striated muscle of arms and legs. Lower motor neurons: peripheral nerve that come out of ventral root. Each muscle fiber is innervated by a single axon. Motor unit is defined as an alpha motor neuron and all muscle fibers it innervates. Motor neuron pool: all the alpha motor neurons that innervate one muscle. To control fine motor movement: more motor units. Innervation ratio=number of muscle cells per motor neuron. Low for fine motor control and high for gross motor control. Fewer muscle fiber innervated by a single axon: more discrete kinds of movement. Muscle that need to be quickly and finely moved have very few muscle fibers innervated per alpha motor neuron. Excitatory postsynaptic potential: neurotransmitters open gates to let in positive ions, have to reach threshold to generate action potential.
