The effect that a neurotransmitter has on the postsynaptic membrane depends on

The gray matter of the spinal cord is mainly

The primary motor cortex is the surface of the

A dorsal and ventral root of each spinal segment unite to form a

________ line the brain ventricles and spinal canal.

A synapse is

Communication across a synapse usually involves the release of

The gray matter of the spinal cord:

The withdrawal, or flexor, reflex is one of the only voluntary reflexes.

Which of these glial cells can form a myelin sheath around axon fibers in the central nervous system?