The coccygeal plexus is a plexus of nerves near the coccyx bone. This plexus is formed by the coccygeal nerve, it gives rise to the anococcygeal nerve. Coccydynia Ganglion impar Sacral plexus Description at uams.edu Coccyx pain
Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defined nervous systems, their neuroanatomy is therefore better understood. In vertebrates, the nervous system is segregated into the internal structure of the brain and spinal cord and the routes of the nerves that connect to the rest of the body; the delineation of distinct structures and regions of the nervous system has been critical in investigating how it works. For example, much of what neuroscientists have learned comes from observing how damage or "lesions" to specific brain areas affects behavior or other neural functions. For information about the composition of non-human animal nervous systems, see nervous system. For information about the typical structure of the Homo sapiens nervous system, see human brain or peripheral nervous system; this article discusses information pertinent to the study of neuroanatomy.
The first known written record of a study of the anatomy of the human brain is the ancient Egyptian document the Edwin Smith Papyrus. The next major development in neuroanatomy came from the Greek Alcmaeon, who determined that the brain and not the heart ruled the body and that the senses were dependent on the brain. After Alcmaeon’s findings, many scientists and physicians from around the world continued to contribute to the understanding of neuroanatomy, notably: Galen, Herophilus and Erasistratus. Herophilus and Erasistratus of Alexandria were the most influential Greek neuroscientists with their studies involving dissecting the brains. For several hundred years afterward, with the cultural taboo of dissection, no major progress occurred in neuroscience. However, Pope Sixtus IV revitalized the study of neuroanatomy by altering the papal policy and allowing human dissection; this resulted in a boom of research in neuroanatomy by scientists of the Renaissance. In 1664, Thomas Willis, a physician and professor at Oxford University, coined the term neurology when he published his text Cerebri anatome, considered the foundation of neuroanatomy.
The subsequent three hundred and fifty some years has produced a great deal of documentation and study of the neural systems. At the tissue level, the nervous system is composed of neurons, glial cells, extracellular matrix. Both neurons and glial cells come in many types. 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 across synapses, produce our memories and movements. Glial cells maintain homeostasis, produce myelin, provide support and protection for the brain's neurons; some glial cells can propagate intercellular calcium waves over long distances in response to stimulation, release gliotransmitters in response to changes in calcium concentration. The extracellular matrix provides support on the molecular level for the brain's cells. 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 modular and serve a particular role within the general pathways of the nervous system. For example, the hippocampus is critical for forming memories; the nervous system contains nerves, which are bundles of fibers that originate from the brain and spinal cord, branch to innervate every part of the body. Nerves are made of the axons of neurons, along with a variety of membranes that wrap around and segregate them into nerve fascicles; the vertebrate nervous system is divided into the peripheral nervous systems. The central nervous system consists of the brain and spinal cord, while the peripheral nervous system is made up of all the nerves outside of the CNS that connect it to the rest of the body; the PNS is further subdivided into the autonomic nervous systems. The somatic nervous system is made up of "afferent" neurons, which bring sensory information from the sense organs to the CNS, "efferent" neurons, which carry motor instructions out to the muscles; the autonomic nervous system has two subdivisions, the sympathetic and the parasympathetic, which are important for regulating the body's basic internal organ functions such as heartbeat, breathing and salivation.
Autonomic nerves, like somatic nerves, contain efferent fibers. In anatomy in general and neuroanatomy in particular, several sets of topographic terms are used to denote orientation and location, which are referred to the body or brain axis; the pairs of terms used most in neuroanatomy are: Dorsal and ventral: dorsal loosely refers to the top or upper side, ventral to the bottom or lower side. These descriptors referred to dorsum and ventrum – back and belly – of the body; the case of the head and the brain is peculiar, since the belly does not properly extend into the head, unless we assume that the mouth represents an extended belly element. Therefore, in common use, those brain parts that lie close to the base of the cranium, through it to the mouth cavity, are called ventral – i.e. at its bottom or lower side, as defined above – whereas