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Neurons are the primary components of the nervous system, along with the glial cells that give them structural and metabolic support. [5] The nervous system is made up of the central nervous system, which includes the brain and spinal cord, and the peripheral nervous system, which includes the autonomic, enteric and somatic nervous systems. [6]
Dissection of a human brain with labels showing the clear division between white and gray matter. Microscopically, there are differences between the neurons and tissue of the CNS and the peripheral nervous system (PNS). [11] The CNS is composed of white and gray matter. [9] This can also be seen macroscopically on brain tissue.
The connections between neurons can form neural pathways, neural circuits, and larger networks that generate an organism's perception of the world and determine its behavior. Along with neurons, the nervous system contains other specialized cells called glial cells (or simply glia), which
Afferent nerves conduct sensory information from sensory neurons to the central nervous system, for example from the mechanoreceptors in skin. Bundles of afferent fibers are known as sensory nerves. [1] [2] Efferent nerves conduct signals from the central nervous system along motor neurons to their target muscles and glands.
Thus, the fundamental difference between a neuron and a nonneuronal cell is a matter of degree. Another major class of cells found in the nervous system are glial cells. These cells are only recently beginning to receive attention from neurobiologists for being involved not just in nourishment and support of neurons, but also in modulating ...
Neurons form complex biological neural networks through which nerve impulses (action potentials) travel. Neurons do not touch each other (except in the case of an electrical synapse through a gap junction); instead, neurons interact at close contact points called synapses. A neuron transports its information by way of an action potential.
There are more than 86 billion neurons in the brain, and a more or less equal number of other cells. Brain activity is made possible by the interconnections of neurons and their release of neurotransmitters in response to nerve impulses. Neurons connect to form neural pathways, neural circuits, and elaborate network systems.
Ramón y Cajal's drawing of the cells of the chick cerebellum, from Estructura de los centros nerviosos de las aves, Madrid, 1905. The neuron doctrine is the concept that the nervous system is made up of discrete individual cells, a discovery due to decisive neuro-anatomical work of Santiago Ramón y Cajal and later presented by, among others, H. Waldeyer-Hartz. [1]