Pelicula la soldadera online dating
In vertebrate species it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body.Nerves that transmit signals from the brain are called motor or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory or afferent.
Nerves are large enough to have been recognized by the ancient Egyptians, Greeks, and Romans, but their internal structure was not understood until it became possible to examine them using a microscope.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.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.Recent findings indicate that glial cells, such as microglia and astrocytes, serve as important resident immune cells within the central nervous system.
The vertebrate nervous system can also be divided into areas called grey matter ("gray matter" in American spelling) and white matter.
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.
White matter is composed mainly of myelinated axons, and takes its color from the myelin.
A protoplasmic fiber runs from the cell body and branches profusely, with some parts transmitting signals and other parts receiving signals.
Thus, most parts of the insect brain have passive cell bodies arranged around the periphery, while the neural signal processing takes place in a tangle of protoplasmic fibers called neuropil, in the interior.
Both autonomic and enteric nervous systems function involuntarily.