1. BIOLOGY & BEHAVIOR
I. THE NERVOUS SYSTEM

2. I. THE NERVOUS SYSTEM I. Neurons - nerve cells that provide
Nervous System: System that regulates the body's responses to internal & external stimuli. Consists of the A. Central Nervous System
B. Peripheral Nervous System
I. Neurons - nerve cells that provide
communication through the body
Quick Fact: Each of us has more than 100 billion neurons in our body, most of which are found in the brain.
The Nervous system is involved in thinking, dreaming, feeling, moving, and much more. It works wether we are sleeping or awake. It regulates our internal functions. It is also involved in how we react to the external world. LEARNING and memory take place because of the nervous system.
It consists of two main parts: the central nervous system and the peripheral nervous system
Neurons - They run through the entire body and communicate with each other. Neurons are nerve cells that provide communication through the body.
Neurons are somewhat like trees in structure. Parts of neurons resemble the branches, trunk, and roots of a tree. And like in forests, many nerve cells lie along each other like trees. UNLIKE trees, however neurons can also lie end to end - so their “root” are intertwined with the “branches” of neurons that lie below.

3. I. NEURONS - Continued
Dendrites
• Dendrites -receives impulses & conducts them to the cell body
Cell Body
• Cell Body -produces energy for the cell
(Don’t Have to Write This down) -
Quick Fact: Dendrites can be damaged by alcohol abuse.
• Myelin -insulates & protects the axon
Myelin Sheath
Axon Terminals
Axon
• Axon - carries messages away from the cell body
Cell Body -produces energy for the cell. It the cell’s life support center.
Dendrites -receives impulses & conducts them to the cell body
Axon - carries messages away from the cell body. Passes the message through its terminal branches to other neurons or to muscles or glands. Dendrites listen. Axons speak. Unlike the short dendrites, axons may be very long, projecting several feet through the body.
Example: A human neuron carrying orders to a leg muscle has a cell body and axon roughly on the scale of a basketball attached to a rope 4 miles long.
In our diagram above, the message is carried from left to right, from the dendrites to the axon, to the axon terminals.
Myelin Sheath -insulates & protects the axon. Think of an electrical cord plugging into your wall or all the different colored cables that connect you phones to a charger. The actual wire is inside the plastic cable. The myelin sheath is that plastic around the wire. It makes insulates them or makes sure that the wire inside doesn’t touch anything else. If the myelin sheath degenerates, multiple sclerosis results: Communication to muscles slows, with eventual loss of muscle control.
A. Components of a Neuron