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Nervous System

The Nervous System is a complicated system that involves specialized cells called nerves that are the primary form of communication between cells and organs throughout the body.

This communication allows for such actions as: muscle contraction, thoughts to proceed, actions to be made, and others.

The Nervous system detects changes in the environment around it and this can lead to changes that impact the body causing some sort of response. Often, these responses are known or unknown to the body itself.

How the body reacts or changes is based on a very complicated set of circumstances, hormones, situations, age, and many more components. The nervous system contains two main categories of type of cells: Neurons and Glial Cells.

The Overall Nervous System is divided into 2 categories or parts:

1.)  Peripheral Nervous System
2.)  Central Nervous System

Peripheral Nervous System (PNS)

–  The PNS is located distinctly outside the Central nervous system.
–  The Central nervous system consists of the brain and spinal cords.
–  The function of the PNS is to allow the central nervous system to connect with the limbs and organs.
–  The PNS is divided into three separate Subsystems: the Somatic, Autonomic, and Enteric Nervous Systems.

1.)  Somatic System mediates voluntary movement

2.)  Autonomic System is further divided into Sympathetic and Parasympathetic Systems. Sympathetic is activated in cases of emergencies to mobilize energy. The Parasympathetic is activated when the body is in a relaxed state.

3.)  Enteric System has a primary goal of controlling the Gastrointestinal System.

Central Nervous System (CNS)

–  The CNS is found within the meninges of the brain.
–  The main function of the CNS is the reception of information, the processing of that information, and often the decision or reaction made to the information.
–  The CNS is quite complex and the location is extensive

Spinal Cord

–  The spinal cord is protected by the bone of the vertebral column.
–  The function of the spinal cord is the conduction of impulses from the brain to the peripheral nervous system to extremities and back again.
–  There are 31 segments of the spinal cord.
–  The complexity of the nervous system is often regulated by signals and neurotransmitters that transmit from one neuron to another.
  –  Neurons are a main component of the nervous system.

Neurons

–  These are the cells that react and act in the process of receiving and transmitting information by signaling.
–  They are an important function of the nervous system.
–  Neurons themselves can differ greatly – some allow for touch, visual, light, smell, sound, and many others. 
–  Neurons in limbs receive stimuli and transfer or send the signal to the spinal cord and to the brain.

Within the nervous system are several cells with complex responsibilities:

1.)  Microglia

–  Are specialized cells of the Nervous system
–  Act as macrophages
–  Can protect neurons
–  Found in brain and spinal cord
–  Are mobile

2.)  Astrocytes

–  Are apart of the CNS system
–  Are shaped in a pattern of a star
–  Helps maintain the cells of the blood-brain barrier
–  Helps remedy any injury to the brain
–  Has a role in scar formation

3.)  Ependymal

–  Are apart of the CNS system
–  Cells that line the brain and spinal cords
–  Helps produce cerebrospinal fluid (CSF)

4.)  Oligodendroglia

–  Are an aspect of the CNS system
–  Similar to Schwann cells of the PNS
–  Wraps around the axon
–  Forms the myelin sheath
–  Can wrap around 40-50 axons

5.)  Schwann

–  Are apart of the PNS
–  Similar to Oligodendroglia of the CNS
–  Wraps around the axon
–  Forms the myelin sheath
–  Can wrap around only 1 axon
–  Permits Nodes of Ranvier

6.)  Satellite

–  Are apart of the PNS
–  Are linear Schwann cells
–  Believed to be similar to Astrocytes in CNS
–  Supply nutrients to cells