Structure of a Neuron:

1.  The control center of neuron is its soma or cell body.

2.  The dense mesh of microtubules and neurofibrils (actin filaments) that compartmentalize the rough ER are called Nissl bodies.

3.  The primary site for receiving signals are called dendrites.

4.  The cylindrical nerve fiber originating from soma responsible for rapid conduction of nerve signals to other cells is called the axon.

5.  The small swellings that form a junction (synapse) with a muscle cell or another neuron are called synaptic knobs.





Classification of Neurons

Neurons are classified structurally according to the number and arrangement of processes extending from the soma.




neuronal variety.jpg

Multipolar, one axon and two or more dendrites, most common







Bipolar, one axon and one dendrite






Unipolar, only a single process leading away from the soma, also called pseudounipolar




Anaxonic, have multiple dendrites but no axon





Supporting cells (neuroglia)

Neuroglial cells protect the neurons and aid their function.


Types of Neuroglia (Glial Cells)

glial cells.jpg




•Ependymal cells

•Microglia cells



•Schwann cells (neurilemmocytes)

•Satellite cells



Myelin Is an insulating layer around a nerve fiber, it is formed by oligodendrocytes in the CNS and Schwann cells in the PNS.



The speed at which a signal travels along a nerve fiber depends on two factors: the diameter of the fiber and the presence or absence of myelin. Myelination of nerve fibers speed up the conduction of the electrical signal on the axon of the nerve fibers.   Also, because signal conduction occurs along the surface of a nerve fiber not deep within its axoplasm, large fibers conduct signals more rapidly than small fibers.