study of neuroanatomy by altering the papal policy and allowing human dissection. This resulted in a flush of new activity by artists and scientists of the Renaissance, such as Mondino de Luzzi, Berengario da Carpi, and Jacques Dubois, and culminating in the work of Andreas Vesalius. In 1664, Thomas Willis, a physician and professor at Oxford University, coined the term neurology when he published his text Cerebri Anatome which is considered the foundation of modern neuroanatomy. The subsequent three hundred and fifty some years has produced a great deal of documentation and study of the neural system. Composition At the tissue level, the nervous system is composed of neurons, glial cells, and extracellular matrix. Both neurons and glial cells come in many types (see, for example, the nervous system section of the list of distinct cell types in the adult human body). Neurons are the information-processing cells of the nervous system: they sense our environment, communicate with each other via electrical signals and chemicals called neurotransmitters which generally act across synapses (close contacts between two neurons, or between a neuron and a muscle cell; note also extrasynaptic effects are possible, as well as release of neurotransmitters into the neural extracellular space), and produce our memories, thoughts, and movements. Glial cells maintain homeostasis, produce myelin (oligodendrocytes), and provide support and protection for the brain's neurons. Some glial cells (astrocytes) can even propagate intercellular calcium waves over long distances in response to stimulation, and release gliotransmitters in response to changes in calcium concentration. Wound scars in the brain largely contain astrocytes. The extracellular matrix also provides support on the molecular level for the brain's cells, vehiculating substances to and from the blood vessels. At the organ level, the nervous system is composed of brain regions, such as the hippocampus in mammals or the mushroom bodies of the fruit fly. These regions are often modular and serve a particular role within the general systemic pathways of the nervous system. For example, the hippocampus is critical for forming memories in connection with many other cerebral regions. The peripheral nervous system also contains afferent or efferent nerves, which are bundles of fibers that originate from the brain and spinal cord, or from sensory or motor sorts of peripheral ganglia, and branch repeatedly to innervate every part of the body. Nerves are made primarily of the axons or dendrites of neurons (axons in case of efferent