Neuron

•  Neurons are the cells considered to be the basis of nervous tissue.
•  Nervous tissue is composed of two types of cells, neurons and glial cells.
• Neurons are electrically active and release chemical signals to target cells.
• Glial cells, or glia, are known to play a supporting role for nervous tissue.
• Neuron -  responsible for the electrical signals that communicate information about sensations, and that produce movements in response to those stimuli, along with inducing thought processes within the brain.
• The main part of a neuron is the cell body, which is also known as the soma (soma = “body”).
• processes of the neuron are dendrites, which receive information from other neurons at specialized areas of contact called synapses.

• Types of Neurons- 

1. Unipolar neuron, 
2. Bipolar neurons, 
3. Multipolar neurons 

• Unipolar cells have only one process emerging from the cell.
• Bipolar cells have two processes, which extend from each end of the cell body, opposite to each other.  found in olfactory epithelium
• Multipolar neuron-have one axon and two or more dendrites (usually many more).

• Glial cells, or neuroglia or simply glia, are the other type of cell found in nervous tissue.
• Glial cell is supporting cells, and many functions are directed at helping neurons complete their function for communication.
• Six types of glial cell four are found in CNS and two are found in PNS.
• CNS glia              PNS glia                  Basic function

1. Astrocyte                 Satellite cell                     Support
2. Oligodendrocyte   Schwann cell                  Insulation, myelination
3. Microglia -  -                                       Immune surveillance and phagocytosis
4. Ependymal cell        -                                        creating CSF

Glial cells support neurons in the central nervous system are 

1. by maintaining the concentration of chemicals in the extracellular space.
2. removing excess signaling molecules, 
3. reacting to tissue damage, and contributing to the blood-brain barrier (BBB).

• Nutrient molecules, such as glucose or amino acids, can pass through the BBB, but other molecules cannot.
•   Myelin is a lipid-rich sheath that surrounds the axon and by doing so creates a myelin sheath that facilitates the transmission of electrical signals along the axon. 
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The posterior horn is responsible for sensory processing and contain the axons of sensory neurons and the cell bodies of interneurons.