The nervous system is part of an animal that coordinates its actions by transmitting signals to and from different parts of the body. The nervous system detects environmental changes that affect the body and then works with the endocrine system to respond to such events. Nervous tissue first developed in worm organisms around 550 to 600 million years ago.
In vertebrates, it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord.
The intestinal system acts to control the gastrointestinal tract. Both the autonomic and intestinal nervous system act involuntarily. The nerves that come out of the skull are called cranial nerves, while those coming out of the spinal cord are called spinal nerves.
At the cellular level, the nervous system is defined by the presence of a special type of cell called a neuron, also called a “nerve cell”. Neurons have special structures that allow them to quickly and accurately send signals to other cells. They send these signals in the form of electrochemical waves moving along thin fibers called axons, which cause the release of chemical compounds called neurotransmitters at intersections called synapses.
The cell that receives the synaptic signal from the neuron can be excited, inhibited or otherwise modulated. Connections between neurons can create neural pathways, neural circuits and larger networks that generate the body’s perception of the world and determine its behavior. Together with neurons, the nervous system contains other specialized cells called glial cells (or simply glial cells) that provide structural and metabolic support.
The only multicellular animals that do not have the nervous system are sponges, rods and mesozoans that have very simple body plans. The nervous systems of organisms with radiant ctenophore symmetry (comb jelly) and cnidarians (which include anemones, hydras, corals and jellyfish) consist of a network of dispersed neurons.
All other species of animals, with the exception of several types of worms, have a nervous system containing the brain, a central core (or two cables running parallel) and nerves radiating from the brain and central cord. The size of the nervous system varies from a few hundred cells in the simplest worms to about 300 billion cells in African elephants.
central nervous system
The central nervous system works to send signals from one cell to another or from one part of the body to the other and receive feedback. The improper functioning of the nervous system may occur as a result of genetic defects, physical damage caused by trauma or toxicity, infection or simply aging.
The medical specialty of neurology examines the nervous system disorders and looks for interventions that can prevent or cure them. In the peripheral nervous system, the most common problem is the failure of the nerve conduction, which may be due to various causes, including diabetic neuropathy and demyelinating disorders such as multiple sclerosis and amyotrophic lateral sclerosis. Neuroscience is a field of science that focuses on the study of the nervous function.
Many types of neurons have an axon, a protoplasmic protrusion that can extend to distant parts of the body and create thousands of synaptic contacts, axons typically extend in the body in bundles called nerves. Even in the nervous system of a single species, such as humans, there are hundreds of different types of neurons with a wide range of morphology and function.
These include sensory neurons that transform physical stimuli, such as light and sound into neural signals and motor neurons that transmute neural signals to activate the muscles or glands; however, in many species the vast majority of neurons participate in the creation of centralized structures (brain and ganglia) and they receive all their contributions from other neurons and send their results to other neurons .
Glial cells (called “glue” from the Greek) 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 glia score is more or less equal to the number of neurons. The proportions vary in different areas of the brain.
The most important functions of glial cells are to support neurons and keep them in place; provide nutrients to neurons; isolate neurons electrically; destroy pathogens and remove dead neurons; and providing guidance to guide the neuron axons for their purposes.
A very important type of glial cells oligodendrocytes in the central nervous system. Schwann cells in the peripheral nervous system produce layers of the fatty substance. It,s called myelin that wraps around axons. It,s provides electrical isolation that allows them to transfer functional and efficient potentials much more quickly. Recent findings indicate that glial cells, such as microglia and astrocytes. The important resident immune cells within the central nervous system.