1. The Nervous System and its Parts
Your nervous system is living tissue composed of cells.
Neurons are the individual cells in the nervous system that receive, integrate and transmit information.
Neurons are the basic links that permit communication within the nervous system.
There are 6 main parts to a neuron.

2. Dendrites
Terminal buttons and synapses
Soma
Axon
Myelin Sheath
Nucleus
Soma: cell body, contains the cell nucleus and much of the machinery common to most cells.
Dendrites: are the parts of the neuron that are specialized to receive information. From here information flows into the cell body and way from the soma along the axon.
Axon: a long thin fiber that transmits signals away from the soma to other neurons or to muscles or glands.

3. In humans, many axons are wrapped in cells with a high concentration of a white, fatty substance called myelin.
The myelin sheath is insulating material that encases some axons.
The axon ends in a cluster of terminal buttons, which are small knobs that secrete chemicals called neurotransmitters.
The points at which neurons interconnect are called synapses—a junction where information is transmitted from one neuron to another.
To summarize, information is received at the dendrites, and is passed through the soma, along the axon, and is transmitted to the dendrites of the other cells at meeting points called synapses.

4. The Nervous System
Experts believe that there are roughly 100 billion neurons in the human brain. These neurons work together to keep information flowing effectively.
There are various parts of the nervous system that all work together to accomplish this.
Peripheral Nervous System
Central Nervous System
Peripheral Nervous System
Brain
Spinal Chord
Somatic Nervous System

5. Peripheral Nervous System
The first and most important division separates the central nervous system (the brain and the spinal chord) from the peripheral nervous system.
The peripheral nervous system is made up of all those nerves that lie outside the brain and the spinal chord.
Nerves are bundles of neuron fibers (axons) that are routed together in the peripheral nervous system.
The Peripheral nervous system can be divided into the somatic nervous system and the autonomic nervous system.

6. Peripheral NS: Somatic NS
The somatic nervous system is made up of nerves that connect to voluntary skeletal muscles and to sensory receptors.
Somatic nerves are two way streets with incoming and outgoing lanes. The somatic nervous system lets you feel the world and move around in it.

7. Peripheral NS: Autonomic NS
The autonomic nervous system is made up of nerves that connect to the heart, blood vessels and smooth muscles and glands.
The autonomic nerve system is a separate system, although it is ultimately governed by the central nervous system.
The autonomic nervous system controls automatic, involuntary, visceral functions that people don’t normally think about like heart rate, digestion and perspiration.
It also controls the fight or flight response that humans get in stressful situations.
The autonomic nervous system can be subdivided into two branches; the sympathetic division and the parasympathetic division.

8. Autonomic Nervous System
The sympathetic division is the branch of the autonomic NS that mobilizes the bodies resources for emergencies.
The parasympathetic division is the branch of the autonomic nervous system that mobilizes the body’s resources for emergencies.
This is the branch that generally conserves bodily resources.

9. The Central Nervous System
The central nervous system is the portion of the nervous system that lies within the skull and spinal column.
Thus, the central nervous system consists of the brain and the spinal chord.
In addition the central nervous system is bathed in its own special fluid that nourishes the brain and provides a protective cushion for it. (cerebrospinal fluid)
The spinal chord connects the brain to the rest of the body through the peripheral nervous system. In short, the spinal chord is an extension of the brain
The spinal chord runs from the base of the brain to just below the level of the waist. It houses bundles of axons that carry the brains commands to the peripheral nerves and that relay sensations from the periphery of the body to the brain.