Neurons: The Building Blocks of the Nervous System.

Essential Question: How are neurons structured and how do they send and receive information within the nervous system?

Part I: The Structure of Neurons

A. What is a Neuron???

A Neuron is a cell that has been specifically designed to receive, transit, and interpret information by sending and receiving electrical impulses.

These neurons communicate with each other throughout the nervous system.

Your nervous system is made up of hundreds of billions of neurons that must work together for you to maintain proper mental health.

-Unlike most other cells, neurons cannot reproduce, so if they die, you lose them forever.

B. Parts of the Neuron

Axon of anotherneuron

Axon of anotherneuron

Cell BodyCell BodyDendritesDendrites

AxonAxon

MyelinSheathMyelinSheath

Dendrites of another neuron

Dendrites of another neuron

1. Cell Body

Contains the nucleusContains the genetic information within the cell

Commands the rest of the cell in what to do, when and how to do it

2. Dendrites

The bushy, branching parts of the neuron

Their job is to receive impulses (messages) from other neurons and pass the information on to the cell body

3. Axon

The extension of the nerve cell It ends in the terminal buttonsAt these terminal buttons, the impulse either ends or is passed on to the next neuron

4. Myelin Sheath

This is primarily a protective structure It insulates the axon and allows the electrical impulses to pass down the axon without the information being lost

C. Glial Cells: The Neurons’ Wingmen

Glial Cells are supporting cells for your neurons

-Literally provide structural support and nutrients to the neuronThey cover the neurons in a myelin sheath to protect them

They also clear debris from building up in the neuron

An Astrocyte connecting a capillary and a nerve:

Neuron Experiment:

Congratulations, we are all now neuronsWe must create a chain that allows us to pass information from one neuron to the next neuron

We will start simple and become more complexWe will try to pass one piece of information first and then progressively get more difficult

The shortest person will start and the tallest person will finish

SUMMARY: HOW DOES OUR EXPERIMENT MIMIC WHAT IS ACTUALLY OCCURING WITHIN THE NERVOUS SYSTEM?

Part II: How Neurons Function

A. Primary Role of Neurons

A neuron’s main role in the body is to collect, interpret, and pass on impulses throughout the Nervous System

This is a vastly important role, however, because our nervous system controls every other system in the body

This is, however, a vastly complicated series of events that requires constant adjustments and clockwork precicion

B. Neurotransmitters: The Messages

The information that is passed through the nervous system is contained in neurotransmitter

These neurotransmitters contain small pieces of chemical information that is specifically designed for delivery to a certain part of the system

There are many types of neurotransmitters with specific roles in the nervous system

C. Action Potential:

When dendrites stimulated, the delicate balance is altered

Positively charged ions rush down the axon Causes release of chemicals from terminal buttons

across the synapse into the next neuron

D. Power of the Myelin Sheath:

The myelin sheath insulates the axon

It also controls the amount of action potential within the axon

Generally speaking, the thicker the myelin sheath, the faster the impulse travels

E. Across the Synapse:

Once the action potential has been realized, the terminal buttons release the neural transmitters to the next cell

They must cross the synapse to the dendrites of the next neuron

If they fail to release the information, the command is stopped within that neuron

F. The end of the Impulse:

At some point, the impulse will end within one neuronThe reality is, however, that an alternate impulse now is sent back to the brain in the case of the sensory nerves

Sensory (Afferent) vs. Motor (Efferent)

e.g., skin

e.g., muscle

Gray’s Anatomy 38 1999

sensory (afferent) nerve

motor (efferent) nerve

Neurons that send signals from the senses, skin, muscles, and internal organs to the CNS

Neurons that transmit commands from the CNS to the muscles, glands, and organs