Grey matter (which is only grey in preserved tissue, and is better described as pink or light brown in living tissue) contains a high proportion of cell bodies of neurons.
Typically, each body segment has one ganglion on each side, though some ganglia are fused to form the brain and other large ganglia.
The head segment contains the brain, also known as the supraesophageal ganglion.
It controls the mouthparts, the salivary glands and certain muscles.
Many arthropods have well-developed sensory organs, including compound eyes for vision and antennae for olfaction and pheromone sensation.
White matter includes all of the nerves, and much of the interior of the brain and spinal cord.
Grey matter is found in clusters of neurons in the brain and spinal cord, and in cortical layers that line their surfaces."It is difficult to believe that until approximately year 1900 it was not known that neurons are the basic units of the brain (Santiago Ram? Equally surprising is the fact that the concept of chemical transmission in the brain was not known until around 1930 (Henry Hallett Dale) and (Otto Loewi).We began to understand the basic electrical phenomenon that neurons use in order to communicate among themselves, the action potential, in the decade of 1950 (Alan Lloyd Hodgkin, Andrew Huxley and John Eccles).The neurons that give rise to nerves do not lie entirely within the nerves themselves—their cell bodies reside within the brain, spinal cord, or peripheral ganglia Glial cells (named from the Greek for "glue") are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system.In the human brain, it is estimated that the total number of glia roughly equals the number of neurons, although the proportions vary in different brain areas.The nervous system is the part of an animal's body that coordinates its actions and transmits signals to and from different parts of its body.