Structure of a Neuron

All neurons are composed of a cell body, dendrites and an axon.[1][3]

 The axon leaves the cell body and connects to other neural cells. Dendrites bring electrical signals to the cell body and axons take information away from the cell body.[1]

Cell body

The cell body contains the organelles necessary to maintain the cells structure and function and is considerec the center of the nerve cell. For example the nucleus, containing genetic information about the cell, the mitochondria and ribosomes.

Dendrites

 A neuron may have one or more dendrites. The dendrites extend from the cell body an increase the receptive surface of the neuron. Their function is to receive information for the neuron to process.

Axon

All neuron types have only one axon, the axon is used to transmit the neuron's output to the connected neighbour. The axon is coated with a protective and insulating layer of myelin. 

Synapses

The place of contact between an axon of one neuron and the dendrite and cell body of another neuron is called a synapse. Neurons are electrically excitable and they process and transmit information. They communicate with each other via chemical and electrical synapses, in a process known as synaptic transmission. 

Glial Cells

The neurons are supported glial cells ("glia" is Greek for "glue"). Unlike neurons, glial cells do not conduct electrical impulses. The glial cells surround neurons and provide support for and insulation between them.[4]

Glial cells are the most abundant cell types in the central nervous system. Types of glial cells include oligodendrocytes, astrocytes, ependymal cells, Schwann cells, microglia, and satellite cells.

Glial cells are divided into microglia and macroglia.

Microglia

These cells are specialized macrophages, small compared to macroglia and their purpose is to protect the neural cells. They are responsible for the immune reaction if any pathogens enter the nervous system.

In a healthy brain, these cells also sample all aspects of their environment and direct the immune response to brain damage and play an important role in the inflammation that accompanies the damage.

Many diseases of the nervous system are associated with abnormalities of microglia - for example Parkinson's or Alzeimer's diseases.

Macroglia

These cells are considerably larger and their functions are varied from supplying the brain with nutritiens to CSF creation.

Astrocytes

The most common glial cells, they link neurons to the blood supply recieved from vessels surrounded by the blood-brain barrier. They can also regulate the chemical environment around the neuron.

Oligodendrocytes 

These cells produce the myelin coating on neurons' axons. The myelin sheath helps electrically insulate the axon and thus make the propagation of electrical impulses more efficient.

Ependymal cells

Line the spinal cord and the ventricular system of the brain and produce the Cerebrospinal fluid.They are also thought to act as neural stem cells.

Radial glia

Facilitate the transport of newly created neurons in a developing brain. In a mature brain, the cerebellum and retina retain characteristic radial glial cells [2]

Types of Neurons by Structure

There are 3 basic types of neurons by structure. These are Unipolar, Bipolar and Multipolar neurons.  [1] [5]

Bipolar 

A neuron with one dendrite and one axon, with the cell body in the middle. Seen in sensory pathways for the special senses of smell, sight, hearing, taste and vestibular sense. They are also extensively used to transfer impulses to muscles. These neurons are the fewest in number.

Unipolar (or pseudo-unipolar)

Most sensory pathways are made from unipolar neurons. These are very similar to bipolar neurons, having one dendrite and one axon, but the difference is that the cell body is not between these two structures, The dendrites are fused to the axon and thus the neuron is optimized to transmit action potentials

Multipolar 

Multipolar neurons are the most common type. They have multiple dendrites leading into the cell body and one output axon. These neurons are able to perform complex analytical or consious processes and make up the vast majority of the brain and spinal cord.

[5]

 Types of Neurons by Function

There are 3 basic types of neurons. These are receptors, effectors and interneurons. [1]  [5]

Receptors / Sensory neurons / Afferent neurons

These neurons send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) TOWARD the central nervous system. These are located in the peripheral nervous system.

Effectors / Motor neurons / Efferent neurons

These neurons send information FROM the central nervous system into the muscles. 

Interneurons

Send information between sensory or motor neurons and the center where the inputs are processed into outputs in the brain. Most interneurons are located in the central nervous system and they make up the bulk of the brain and spinal cord.

Neural Cell Structures

The classification of neurons by structure or by function are very broad and the brain is actually composed of many different and usually very specialized neural cells. This list will name the most important ones.

• Purkinje cells
• Dogiel cells
• Ganglion cells
• Betz cells
• Basket cells
• Stellate cells
• Golgi cells
• Granule cells
• Deep cerebral nuclei
• Pyramidical cells