<P> A neuron, also known as a neurone (British spelling) and nerve cell, is an electrically excitable cell that receives, processes, and transmits information through electrical and chemical signals . These signals between neurons occur via specialized connections called synapses . Neurons can connect to each other to form neural networks . Neurons are the primary components of the central nervous system, which includes the brain and spinal cord, and of the peripheral nervous system, which comprises the autonomic nervous system and the somatic nervous system . </P> <P> There are many types of specialized neurons . Sensory neurons respond to one particular type of stimulus such as touch, sound, or light and all other stimuli affecting the cells of the sensory organs, and converts it into an electrical signal via transduction, which is then sent to the spinal cord or brain . Motor neurons receive signals from the brain and spinal cord to cause everything from muscle contractions and affect glandular outputs . Interneurons connect neurons to other neurons within the same region of the brain or spinal cord in neural networks . </P> <P> A typical neuron consists of a cell body (soma), dendrites, and an axon . The term neurite is used to describe either a dendrite or an axon, particularly in its undifferentiated stage . Dendrites are thin structures that arise from the cell body, often extending for hundreds of micrometers and branching multiple times, giving rise to a complex "dendritic tree". An axon (also called a nerve fiber) is a special cellular extension (process) that arises from the cell body at a site called the axon hillock and travels for a distance, as far as 1 meter in humans or even more in other species . Most neurons receive signals via the dendrites and send out signals down the axon . Numerous axons are often bundled into fascicles that make up the nerves in the peripheral nervous system (like strands of wire make up cables). Bundles of axons in the central nervous system are called tracts . The cell body of a neuron frequently gives rise to multiple dendrites, but never to more than one axon, although the axon may branch hundreds of times before it terminates . At the majority of synapses, signals are sent from the axon of one neuron to a dendrite of another . There are, however, many exceptions to these rules: for example, neurons can lack dendrites, or have no axon, and synapses can connect an axon to another axon or a dendrite to another dendrite . </P> <P> All neurons are electrically excitable, due to maintenance of voltage gradients across their membranes by means of metabolically driven ion pumps, which combine with ion channels embedded in the membrane to generate intracellular - versus - extracellular concentration differences of ions such as sodium, potassium, chloride, and calcium . Changes in the cross-membrane voltage can alter the function of voltage - dependent ion channels . If the voltage changes by a large enough amount, an all - or - none electrochemical pulse called an action potential is generated and this change in cross-membrane potential travels rapidly along the cell's axon, and activates synaptic connections with other cells when it arrives . </P>

Neurons contain which can receive signals from other neurons