When Responding to Stimulation of the Outer Margin of the Sole

Multiple Choice

When responding to stimulation of the outer margin of the sole of the foot,a 1-year-old infant extends her great toe without fanning of the other toes.This happens because:

A) the corticospinal fibers have become fully myelinated and the Babinski reflex becomes suppressed.
B) the corticospinal fibers have not yet become fully myelinated and the Babinski reflex is activated.
C) the sensory fibers in the ophthalmic branch of the fifth cranial nerve are mediated by reflex arcs.
D) a deep reflex is mediated by a two-neuron spinal arc.