Neuron, being a structural and functional unit of the nervous system, is a highly specialized cell that is able to generate and conduct electrical impulses.During the evolutionary process, the neurons lose their ability to divide, and therefore can not breed.Hence there was a well-known expression of the people, "the nerve cells do not regenerate."
Neuron, structure and functions of which are very different, also has a variety of shapes and sizes, depending on the location of the cell.The largest neurons - the giant pyramidal cells - are located in the brain in the cerebral cortex and cerebellum.Obviously, the large size of these cells due to the complexity of the functions they perform.
The main function of the nerve cells is to provide a living organism to adapt to changing environmental conditions, and the person using them has acquired the ability to think.
structure of the neuron only at first glance seems simple.Each cell consists of a body or soma and processes - dendrites and axons.Axon - a long unbranched process whose function is to transmit nerve impulses from one cell to another.Moreover, from a single cell of the body may depart only one such process, this is the morphological feature of the axon.But the number of dendrites, extending from one soma of nerve cells can be conversely large.They interact with the axons and dendrites of other, take a nerve impulse.However, the main receptive field of the neuron are dendrites.Axons end capable of releasing special substances - mediators, which responds to the dendrite membrane.Typically, each neuron has multiple dendrites are highly branched, thus providing a large number of information inputs.Information fed into the cell through specialized contacts, called "spines".They allow neurons to perceive the nerve signal.
The structure also includes a neuron axonal hillock - soma cell site that performs an integrative function using a multi-layer membrane.She's covering the body of the cell, provides the formation, distribution and transmission capacities electrotonic from the soma to the axon hillock.Function soma mostly informational, but it still performs trophic function, which is to ensure the growth and development processes in the body during ontogeny.
By the number of neurons processes are odnootroschatye (unipolar) dvuotroschatye (bipolar) and mnogootroschatye (multipolar).Truly unipolar can only be called the brain's neurons, which are located in the nucleus of the trigeminal proprioception and control of the masticatory muscles.In other respects, the structure of a neuron determines its functionality.Bipolar neurons are the basis of the peripheral nerves auditory, visual and olfactory systems.
special structure enables the neuron to him the main thing - information function due to the special properties of the membrane.She having remarkably small thickness of 6 nm, it consists of only two layers of lipid molecules.It embedded proteins that perform a variety of functions: moving in the cell molecules and ions against the concentration gradient, ensuring selective permeability of membranes, recognition of foreign molecules and maintenance of chemical reactions on the surface of the membrane.
complex structure of the neuron and the variety of functions performed by them allows to classify the nerve cells in many ways:
- the type of the chemical structure of substances released by their axons;
- the type of sensitivity to different stimuli;
- type of functional activity.
