True about lateral coicospinal tract:
Correct Answer: Crossed
Description: A i.e. CrossedCoicospinal (Pyramidal) tractIt originates from primary motor coex (30%), premotor & supplementary motor area (30%) and sornatosensory areas posterior to central sulcus (40%)It passes through posterior limb of internal capsule (b/w caudate nucleus & putamen of basal ganglia) and then form pyramid of medulla.Lateral coicospinal tract (LCT)- 80% of fibers of pyramidal tract cross in lower medulla0 to opposite side & form LCT.Concerned with skilled movements and ends directly on motor neurons in humans (Ganong).But according to Guyton fibers finally terminate on interneurons in intermediate regions of cord gray matter (most) > sensory rely neurons in dorsal horn (few) > directly on anterior motor neurons that cause muscle contraction (very few).Anterior/Ventral - coicospinal tract20% fibers do not cross to opposite side in medullaDo not cross the middle until it reaches the level of muscles it controls. At this level fiber ends on inter neuron that is connected to motor neuron of both sides of body (Ganong) Many (if not most) fibers cross to opposite side of body either in neck or in upper thoracic region (Guyton); and are concerned with control of bilateral postural movements (by supplementary motor coex).Large myelinated fibers originating from giant pyramidal (Betz) cells (found only in primary motor coex) are most impressive fibers in pyramidal tract. Diameter of cell is 60 p m & of fiber is 16 p m (micrometer) with a conduction velocity of 70 m/sec. (most rapid transmission from brain to cord). Total fibers in pyramidal tract is 1 million, of which 3% (34,000) are from Betz cells. Remaining 97% fibers are < 4 p in diameter.
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