Neurons The Building Blocks of the Nervous System

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 Dendrite s Axon of another neuron Cell Body Myelin Sheath Axon Dendrites of another neuron

1. Cell Body Contains the nucleus Contains 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 buttons At 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 An Astrocyte connecting a capillary and a nerve: for your neurons -Literally provide structural support and nutrients to the neuron They cover the neurons in a myelin sheath to protect them They also clear debris from building up in the neuron

Neuron Experiment: Congratulations, we are all now neurons We must create a chain that allows us to pass information from one neuron to the next neuron We will start simple and become more complex We 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 neuron The 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) sensory (afferent) nerve e. g. , skin Neurons that send signals from the senses, skin, muscles, and internal organs to the CNS motor (efferent) nerve Neurons that transmit commands from the CNS to the muscles, glands, and organs Gray’s Anatomy 38 1999 e. g. , muscle