Final answer:
The dendrites are the parts of a neuron that increase surface area for synaptic connections, enhancing the neuron's communicative function. The gray matter is where you find numerous dendrites and neuronal cell bodies, whereas the white matter is composed of myelinated axons that facilitate rapid signal transmission.
Step-by-step explanation:
The region that has the primary function of increasing the surface area for the neuron is the dendrite. Dendrites are tree-like extensions from the neuron's cell body that receive signals from other neurons. Their elaborate branching increases the surface area, allowing for a higher number of synaptic connections with other neurons, thereby enhancing the neuron's ability to receive and process information. The gray matter of the brain and spinal cord predominantly contains these neuronal cell bodies and dendrites. In contrast, the white matter is composed mainly of axons, which are another type of neuronal process. Axons are insulated by myelin, a lipid-rich substance that makes the white matter appear white and facilitates the rapid transmission of electrical signals along the nervous system. Axonal processes can be further facilitated by nodes of Ranvier, gaps between myelinated segments that strengthen the electrical signal as it propagates down the axon.