Question

why are the proportions of the sensory homunculus very different from those of an actual human being? because the number and size of sensory neurons in the sensory homunculus must match the number and size of motor neurons that begin in the motor homunculus of the precentral gyrus; these neurons are also directly in proportion to absolute body size. because the area of the sensory homunculus must fit into the postcentral gyrus, which is smaller than the relative body size, proportionately. because the area of sensory cortex devoted to a particular region is proportional to the number of sensory receptors the region contains. because the area of sensory cortex devoted to a particular body region is proportional to the absolute size of the region. i dont know yet

Explanation:

The sensory homunculus represents the area of the sensory cortex devoted to a body region. It is proportional to the number of sensory receptors (not absolute body size or motor neurons). The postcentral gyrus (where the sensory homunculus is) - its mapping is about receptor density.

Answer:

Because the area of sensory cortex devoted to a particular region is proportional to the number of sensory receptors the region contains.