Which of the following statements is incorrect? a. The white matter of the spinal cord contains tracts. b. The anterior gray horn and posterior gray horns contain myelinated fibers. c. The gray matter of the spinal cord contains unmyelinated interneurons. d. Motor tracts carry information away from the brain. e. Sensory tracts carry information to the brain.

The incorrect statement is b. "The anterior gray horn and posterior gray horns contain myelinated fibers." The gray matter predominantly contains cell bodies of neurons, dendrites, and unmyelinated axons, as well as neuroglia – which are support cells within the nervous system. In contrast, the white matter of the spinal cord is the part that contains myelinated axons, which form tracts.

Extra: Gray matter in the central nervous system, which includes the spinal cord and the brain, is composed of regions with dense collections of neuronal cell bodies, dendrites, and synapses. The color gray comes from the relatively unmyelinated state of the fibers in this area. Myelin is a fatty substance that covers axons and gives the white matter its lighter color. It also aids in the rapid transmission of electrical signals along axons.

In the spinal cord, which is part of the central nervous system, the gray matter is arranged in a butterfly or "H" shape, which divides it into horns. These are known as the dorsal (or posterior), ventral (or anterior), and lateral horns. The ventral horns contain the cell bodies of motor neurons that send axons through the ventral roots of the spinal nerves to innervate the muscles. The dorsal horns contain interneurons and the axons of sensory neurons which bring information from the periphery of the body into the spinal cord.

The white matter of the spinal cord is where myelinated nerve fibers are organized into tracts or columns. These fibers make up ascending tracts that carry sensory information to the brain and descending tracts that carry motor signals from the brain to the effector organs such as muscles.

The functions of the motor and sensory tracts are crucial for the body’s interaction with its environment. Motor tracts, as part of the efferent pathway, carry motor commands from the brain to various parts of the body to perform actions. Sensory tracts, which are part of the afferent pathway, convey sensory information from the receptors in the skin, muscles, and other peripheral organs back to the brain to process and integrate the stimuli received.