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NEURON 
A neuron is an electrically excitable cell that processes and transmits information by 
electrical and chemical signaling. Chemical signaling occurs via synapses, specialized 
connections with other cells. Neurons connect to each other to form networks. Neurons are 
the core components of the nervous system, which includes the brain, spinal cord, and 
peripheral ganglia. A number of specialized types of neurons exist: sensory neurons respond 
to touch, sound, light and numerous other stimuli affecting cells of the sensory organs that 
then send signals to the spinal cord and brain. Motor neurons receive signals from the brain 
and spinal cord, cause muscle contractions, and affectglands. Interneurons connect neurons 
to other neurons within the same region of the brain or spinal cord. 
PARTS OF NEURON 
 
Cell body- The cell body of a neuron is a ball-shaped structure about 0.025 millimetre wide. 
Each neuron cell body is a centre for receiving and sending nerve impulses. The cell body is 
also responsible for making proteins and using energy for the maintenance and growth of 
the nerve cell. The vast majority of neuron cell bodies are within the central nervous system, 
where incoming messages are combined and outgoing messages are produced. The few 
neuron cell bodies outside the central nervous system are grouped into clusters called 
ganglia. The best-known ganglia are in the autonomic nervous system. 
Axon- The axon, also called the nerve fibre, is a tubelike extension of a neuron cell body. 
The axon is specialized to carry messages. An axon of one neuron may have enough 
branches to make contact with as many as 1,000 other neurons. Most axons in the central 
nervous system are less than 1 millimetre long. However, many axons in the peripheral 
nervous system are longer, and some are much longer. For example, the axons that extend 
from the spinal cord to the muscles in the feet may be 75 to 100 centimetres long. The 
structures commonly called nerves are actually bundles of axons lying next to one another in 
a cordlike formation. Nerves can be made up of the axons of motor neurons or sensory 
neurons, or of both. Some axons are covered by a sheath of a white, fatty substance called 
myelin. The myelin increases the speed of impulses along the axons. Myelin also causes the 

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distinction between the grey matter and white matter in the nervous system. Grey matter 
consists largely of unmyelinated axons (axons without myelin sheaths) and neuron cell 
bodies. White matter is made up mostly of axons that have white sheaths of myelin. Myelin 
is formed in the peripheral nervous system by Schwann cells, which are special supporting 
cells that surround the axons. In the central nervous system, supporting cells called glia 
produce myelin. 
Dendrites- The dendrites of a neuron are branching, tubelike extensions of the cell body 
that form a pattern resembling the limbs of a tree. Most neuron cell bodies have about six 
main dendrites, each of which is two or three times as thick as the axon of the cell. The 
distance between the cell body and the tips of the dendrites is about 0.5 millimetre. 
Dendrites are specialized structures for receiving impulses, mostly from the axon of another 
neuron. Dendrites and axons do not quite touch each other. In almost all cases, they are 
separated by an extremely narrow space called the synaptic cleft, over which nerve impulses 
are transmitted. These places where one neuron communicates with another are called 
synapses. 
TYPES OF NEURON 
1. Sensory neurons typically have a long dendrite and short axon, and carry messages from 
sensory receptors to the central nervous system.  
2. Motor neurons have a long axon and short dendrites and transmit messages from the 
central nervous system to the muscles (or to glands).  
3. Interneurons are found only in the central nervous system where they connect neuron to 
neuron. 
Glial cells, sometimes called neuroglia or simply glia, are non-neuronal cellsthat 
maintain homeostasis, form myelin, and provide support and protection for the 
brain's neurons. In the human brain, there is roughly one glia for every neuron with a ratio of 
about two neurons for every glia in the cerebral gray matter. As the Greek name implies, glia 
are commonly known as the glue of the nervous system; however, this is not fully accurate. 
The four main functions of glial cells are to surround neurons and hold them in place, to 
supply nutrients and oxygen to neurons, to insulate one neuron from another, and to 
destroypathogens and remove dead neurons. 
Types of Glia cells 
Microglia are like specialized macrophages capable of phagocytosis that protect neurons of 
the central nervous system. They are derived from hematopoietic precursors rather 
than ectodermal tissue; they are commonly categorized as such because of their supportive 
role to neurons. These cells comprise approximately 15% of the total cells of the central 
nervous system. They are found in all regions of the brain and spinal cord. Microglial cells 
are small relative to macroglial cells, with changing shapes and oblong nuclei. They are 
mobile within the brain and multiply when the brain is damaged. In the healthy central 
nervous system, microglia processes constantly sample all aspects of their environment 
(neurons, macroglia and blood vessels). 
 

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NEURON A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous system, which includes the brain, spinal cord, and peripheral ganglia. A number of specialized types of neurons exist: sensory neurons respond to touch, sound, light and numerous other stimuli affecting cells of the sensory organs that then send signals to the spinal cord and brain. Motor neurons receive signals from the brain and spinal cord, cause muscle contractions, and affectglands. Interneurons connect neurons to other neurons within the same region of the brain or spinal cord. PARTS OF NEURON Cell body- The cell body of a neuron is a ball-shaped structure about 0.025 millimetre wide. Each neuron cell body is a centre for receiving and sending nerve impulses. The cell body is also responsible for making proteins and using energy for the maintenance and growth of the nerve cell. The vast majority of neuron cell bodies are within the central nervous system, where incoming messages are combined and outgoing messages are produced. The few neuron cell bodies outside the central nervous system are grouped into clusters called ganglia. The best-known ganglia are in the autonomic nervous system. Axon- The axon, also called the nerve fibre, is a tubelike extension of a neuron ...
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