NERVOUS SYSTEM AND NEURON MODELING v.2 (online)

As usual, please write responses in complete proper sentences.

Objective

Describe the structure of neurons by constructing and labeling models

Introduction

The brain is made up of billions of individual nerve cells (neurons). Understanding the anatomy of a neuron is key to appreciating its functioning along with the functioning of the entire nervous system, including the brain.

Neurons are the oldest and longest cells in the body! You have many of the same neurons for your whole life. Neurons can be quite large, such as corticospinal neurons (extending from motor cortex to spinal cord) or primary afferent neurons (extending from the skin into the spinal cord and up to the brain stem).

One way to classify neurons is by the number of extensions that extend from the neuron's cell body (soma).

·         Bipolar neurons have two processes extending from the cell body (examples, retinal cells, olfactory epithelium cells).

·         Unipolar cells have two axons rather than an axon and dendrite. One axon extends centrally toward the spinal cord; the other axon extends toward the skin or muscle.

·         Multipolar neurons have many processes that extend from the cell body. However, each neuron has only one axon (examples, spinal motor neurons, pyramidal neurons, Purkinje cells).

Neurons can also be classified by the direction that they send information.

·         Sensory (or afferent) neurons: send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) TOWARD the central nervous system.

·         Motor (or efferent) neurons: send information AWAY from the central nervous system to muscles or glands.

·         Interneurons: send information between sensory neurons and motor neurons. Most interneurons are located in the central nervous system.

A neuron has four basic parts.

·         Dendrites - Extensions from neuron cell bodies that take information to the cell body. Dendrites usually branch close to the cell body.

·         Cell body (soma) - the part of the cell that contains the nucleus.

·         Axon - the extension from the neuron cell body that takes information away from the cell body. A single axon projects out of the cell body.

·         Axon terminal - end part of an axon that makes a synaptic contact with another cell.

What is inside of a neuron? All of the organelles in a typical cell, although some have specialized names.

A reflex arc involves transmission of a nervous impulse or message from sensory receptors to the spinal cord and back to muscles. Later, the message also reaches the brain for interpretation. Reflexes and spinal cord messages travel faster than the messages to the brain. That is why reflexes are defined as involuntary reactions. A reflex arc involves sensory, motor, and interneurons as well as the spinal cord.

Part 1 Modeling Neurons (15 points)

Materials

• Sheets of plain paper, 8.5” x 11”
• Markers or pens
• Neuron parts, see below

Procedure

What can you use to make a model of a neuron? Here are some suggestions. Please do not purchase materials. You can find plenty of items around the house, shop, or yard.

1.       Refer to the figure below and this site for representations of unipolar, bipolar, and multipolar neurons. You will be building models of each.

2.       Find materials. Here are some suggestions.

·         Play dough (recipe on page 3 of lab)

·         Clay

·         Bottle caps

·         Buttons

·         Jelly beans

·         String

·         Colored paper

·         Washers

·         Other things

3.       Plan your first neuron by collecting the organelles and other structures.

4.       On a sheet of paper, build a large cell body on a sheet of paper and add these organelles.

·         Nucleus

·         Nucleolus

·         Golgi

·         Nissl bodies

·         Cytoskeleton

5.       Refer to your text or other references. Cite your sources, even the text book! 

6.       Add the myelin sheath to your model.

7.       Label the four basic parts by writing them on the paper and adding arrows or other ways of designating the parts.

8.       Build the other two types in the same way. All together you will build bipolar, unipolar, and multipolar neurons.

9.       Take a photo of each neuron and add to your blog site.

NEURON

BIPOLAR NEURON

UNIPOLAR NEURON

MULTIPOLAR NEURON

10.   Answer this question. What is a good idea to help remember the directions afferent and efferent neurons sent messages to or from the central nervous system?

 Afferent means inwards or towards and efferent means away.  You first need stimulus in order to get a response. So an easy way to remember is afferent which is stimulus or sensory neurons comes first and efferent is response or motor neurons.