<prompt> When are the axons of the coicospinal tracts fully myelinated?In the late embryonic periodIn the mid-fetal periodAt bihBy the end of the second postnatal year  <response>: Axons of the coicospinal tracts are fully myelinated by the end of the second postnatal year Babinskis sign extensor plantar reflex is usually elicitable before myelination of the coicospinal tracts -reflects poor coical control of motor function by the immature brain. 