Neuron is special kind of animal cell which can generate and conduct electric current. In order to understand the way of generating electric signals, we study its structure.
Structure of neuron:
Neurons differ considerably in size and shape but generally differentiated into following three regions: Soma, dendrites and axon. Soma is also called cell body. It contains cytoplasm and nucleus. In addition to typical cell organelles, it contains Nissl substance which consists of ribosomes. From soma arises a number of thread like processes the dendrites which receive stimuli and convey it to soma.
Axon is long cytoplasmic process which usually arises opposite to dendrites. It is the conducting end of a neuron. It ends in knob like structures, the axon terminals. It originates from a pyramid like area of soma called axon hillock. The axons of some neurons are covered by a myelin sheath.
Types of Neuron:
Functionally neurons can be differentiated into following three types.
(i) Sensory neuron: It carries sensory information from the receptor to other neurons or directly to CNS.
(ii) Motor neuron: It takes commands of the control centre to the effector.
(iii) Inter neuron: They are found in central nervous system. Depending upon the presence or absence of myelin sheath, neurons are called myelinated and un myelinated neuron respectively.
Functions of Neuron:
Neuron is a functional unit of nervous system. It is involved in communication by receiving stimuli, integrating various stimuli and sending appropriate instructions to some of the effector organs.
Neuroglia (Glial cells):
Neurons in central nervous system (CNS) are associated with another type of cells called neuroglia. These smaller separate neurons from one another, from myeline sheath and are also involved in trophic and phagocytic functions. They occur in several structural and functional types.
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