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The anterior corticospinal tract (also called the ventral corticospinal tract, medial corticospinal tract, direct pyramidal tract, or anterior cerebrospinal fasciculus) is a small bundle of descending fibers that connect the cerebral cortex to the spinal cord. Descending tracts are pathways by which motor signals are sent from the brain to lower motor neurons whcih then directly innervate muscle to produce movement. The anterior corticospinal tract is usually small, varying inversely in size with the lateral corticospinal tract, which is the main part of the corticospinal tract. It lies close to the anterior median fissure, and is present only in the upper part of the medulla spinalis; gradually diminishing in size as it descends, it ends about the middle of the thoracic region. It consists of descending fibers that arise from cells in the motor area of the ipsilateral cerebral hemisphere. The impulse travels from these upper motor neurons (located in the pre-central gyrus of the brain) through the anterior column. The pathway decussates in the spinal cord and then synapses at the anterior horn with the lower motor neuron which then synapses with the target muscle at the motor end plate. Similar to the lateral corticospinal tract, the anterior corticospinal tract innervates muscles involved in fine control of the limbs. A few of its fibers pass to the lateral column of the same side and to the gray matter at the base of the posterior column. ==Additional images== Image:Gray680.png|Decussation of pyramids. Image:Gray764.png|The motor tract. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Anterior corticospinal tract」の詳細全文を読む スポンサード リンク
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