Structure and function of the nervous system

The nervous system controls the body, coordinates organs and responds to external and internal stimuli. Nervous tissue consists of nerve cells – neurons – and supporting neuroglia cells that feed and protect them. From the neuron body come one long process, the axon, and several short branched processes, dendrites; dendrites bring impulses to the body and the axon carries them away. The junction of two neurons is a synapse; a chemical released there, the mediator, passes excitation to the next cell. By function neurons are sensory, motor and interneurons; nerves too are sensory, motor or mixed. By location the nervous system is central (brain and spinal cord) and peripheral (nerves and ganglia). By function, the somatic part controls skeletal muscles voluntarily, while the autonomic (vegetative) part controls internal organs outside our will and has sympathetic and parasympathetic parts, which usually act in opposite ways.