Final answer:
Gray matter consists of neuronal cell bodies and dendrites, and includes the thalamus, motor cortex, and basal nuclei. White matter, on the other hand, consists of myelinated axons and includes the corpus callosum and association tracts. Therefore, the thalamus, motor cortex, and basal nuclei are composed of gray matter.
Step-by-step explanation:
To answer which structures are composed of gray matter, it is essential to first understand the arrangement of gray and white matter in the brain and spinal cord. Gray matter primarily consists of neuronal cell bodies, dendrites, and synapses, whereas white matter is made up of myelinated axons that form pathways or tracts for nerve signal transmission.
The structures made up of gray matter include the thalamus, motor cortex, and basal nuclei. The thalamus is a gray matter structure within the diencephalon of the brain, acting as a relay station for sensory and motor signals. The motor cortex is part of the cerebral cortex, involved in planning and executing voluntary movements.