CLASSIFICATION OF NERVE CELLS 1. Cell body Each nerve cell body contains a single nucleus.. This nucleus is the cell control center. The cell body functions to receive stimulation from the dendrites and transmit it to the axon. In the nerve cell body there is the cell nucleus, cytoplasm, mitochondria, centrosomes, Golgi bodies, lysosomes. 2. Dendrites Dendrites are short, branched nerve cell fibers, like tree branches. Dendrites is an extension of the cell body. This is the receptive area of the neuron. Dendrites function to receive and deliver stimuli to the cell body 3. Axon Axon hilock, is a long process or fiber that begins singly but can branches and at the end has many fine extensions called axon terminals that contact the dendrites of other neurons. The fine threads contained in the axon are called neurofibrils. Neurofibrils are wrapped in several layers of myelin membrane which contains lots of fatty substances and functions to speed up the passage of stimulation. On the outside of the axon there is a layer of fat called myelin which is a collection of Schwann cells that attach to the axon. Schwann cells are glial cells that form the fatty sheath around myelinated nerve fibers. The plasma membrane of Schwann cells is called the neurilemma. The function of mielin is to protect acson and give nutrition. The part of the axon that is a narrow gap and is not covered in myelin is called the node of Ranvier, which functions to speed up the transmission of impulses. NERVE TYPES Based on structural differences, nerves are classified into three groups as follows 1. Unipolar nerves Has one nerve fiber from the cell body which then branches into two: one becomes dendrites because they relate to the periphery, others as nerve trunks. Peripheral nerves can be very long and reach one meter. An example is the sensory nerve proprioception (body position). Another example of a sensory nerve that is not long is the nerve to the internal organs (visceral) and taste. 2. Bipolar nerves Has two nerve trunks originating from the nerve body. One functions as a dendrite others as nerve trunks. For example, sensory nerves carry information about vision, smell, balance and hearing. The nerves in the retina carry information from the retina to the ganglion cells, in the inner ear, forming nerve number VIII in the cochlea and vestibular. 3. Multipolar nerves Multipolar nerves have many nerve fibers from one cell body. For example the nerves of the upper part of the brain descends to the spine and then spreads to all the muscles.