Grey matter contains cell bodies of neurons. White matter contains axonal processes plus glial cells. A special fluid bathes the brain and spinal cord and also provides cushioning for the brain. Peripheral tissues of the body and head receive nerves from the spinal cord and not directly from the brain. The dorsal half of the spinal cord contains the sensory nerves, the ventral half the motoneurons.
Nerve cells can reach one meter in length.
Glial cells help wrap axons to enhance propagation of electrical signals. Neurons are often polarized with dendrites exending from the side of the cell opposite the axon. Movement of outer hair cells against the tectorial membrane. Show the direction of light coming into the retina. The cerebellum and the thalamus lie underneath the cerebral cortex.