Chapter 1. Build a Neuron

1.0.1 Build a Neuron

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Build a Neuron
Begin
neuron
Specialized nerve cell engaged in information processing.
dendritic spines
Protrusion that greatly increases the dendrite’s surface area; typical point of dendritic contact with the axons of other cells.
axon collaterals
The axon may branch, often at right angles, into one or many axon collaterals which enable the neuron to communicate with more than one neuron.
terminal branching
The division of an axon’s lower tip into multiple smaller branches, or telodendria, each containing its own terminal button, enabling it to contact more than one location on a target cell.
dendrites
Branching extension of a neuron’s cell membrane; greatly increases the cell’s surface area; collects information from other cells.
axon
Root, or single fiber, of a neuron that carries messages to other neurons.
soma (cell body)
The cell body, which contains the cell nucleus and structures responsible for the life processes of the cell. The shape of the soma varies in different types of neurons. Most molecules essential for the cell’s functions are formed within the soma.
nucleus
A round or oval structure enclosed in a membrane. It contains the nucleolus and the chromosomes, which include the organism’s genetic information in the form of DNA.
axon hillock
Juncture of soma and axon.
synapse
Spatial junction between one neuron and another; forms the information transfer site between neurons.
Myelin sheath
Glial coating that surrounds axons in the central and peripheral nervous systems; increases the speed of neural signaling and prevents signaling interference from adjacent cells.
terminal button
Nob at the tip of an axon that conveys information to other neurons.
sensory neuron
A neuron that carries afferent (incoming) information from the body into the spinal cord and brain.
interneuron
A neuron that integrates sensory and motor information within the central nervous system.
motor neuron
A neuron that carries efferent (outgoing) information from the brain and spinal cord to muscles.
sensory neuron 1sensory neuron
Cell that detects or carries sensory information into the spinal cord and brain.
interneuron 1interneuron
Association cell interposed between a sensory neuron and a motor neuron; in mammals, interneurons constitute most of the brain’s neurons.
motor neuron 1motor neuron
Cell that carries efferent motor information from the brain and spinal cord to make muscles contract.

Build Your Own Neuron

By: Dr. Daniel Hummer, Morehouse College

1.1 Build Your Own Neuron

Build Your Own Neuron

In this activity, you will learn about how the physical structure of a neuron affects the way it functions by manipulating some of its key components.

After completing this activity, you should be able to:

  • Identify the major components of a neuron and describe their corresponding functions
  • Identify and describe different types of neurons
  • Explain how the structure of a neuron relates to its function

This activity relates to the following principles of nervous system function:

  • Principle 1: The Nervous System Produces Movement in a Perceptual World the Brain Constructs
  • Principle 7: Sensory and Motor Divisions Permeate the Nervous System

1.2 Structure of the Neuron 1

Structure of the Neuron 1

The neuron is the basic information-processing and transmission unit of the nervous system. There are various forms and types of neurons, defined according to their functions. Most neurons contain several basic components, including the dendrites, soma (cell body), axon, and terminal buttons. These components enable the reception, processing, and transmission of neural information.

Now let's take some time to explore the major structures of a typical neuron. Select each term below to read a brief description.

Structure of a neuron. The soma is its bulbous part which contains nucleus in the center. There are several short branched extensions of the cell which are called dendrites. The cell also has one long and slender projection named axon. Axon arises from the axon hillock which is the protrusion of the soma. Axon is covered with myelin sheath which is divided into segments interspersed with unmyelinated sections. Dilatation at the end of an axon is called terminal button. It moves closer to a dendrite of another neuron forming a synapse.

Nucleus

Soma

Dendrites

Axon hillock

Axon

Myelin sheath

Synapse

Terminal button

1.3 Structure of the Neuron 2

Structure of the Neuron 2

Before we explore the various types of neurons, let's review the major parts. Select the appropriate label for each part of the neuron below.

Structure of a neuron and its contact with another neuron.

Question

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3
1,2,3,4,5,6,7,8
Large round structure in the center of the cell.!The widest bulbous part of the cell.!Short and branched projection of the cell.!Area extended from the cell where it becomes an axon.!Very long and slender projection of the cell.!Substance forming a sneath around the section of an axon.!Place of contact between an axon of one neuron and a dendrite of another.!The end presynaptic bulb of an axon.
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All answers are correct.
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1.4 How Does Neural Structure Relate to Neural Function?

How Does Neural Structure Relate to Neural Function?
Build Your Neuron

Neurons, as seen from the examples below, can look quite different from each other. A neuron’s function is closely related to its structural features, including (but not limited to) the extent of dendritic branching, number of dendritic spines, number of axon collaterals, length of the axon, and the extent of terminal branching.

Various neurons with different composition. The first neuron has one short dendrite which hardly branches and one short axon. The second neuron has one long dendrite and one long axon, both branching a little. The third neuron has multiple highly branching dendrites. The fourth neuron has one long unbranching axon and several long branching dendrites. The fifth neuron has one long unbranching axon and multiple highly branched dendrites. The sixth neuron has one long unbranched axon and several extensively branched dendrites.

Variation in these structural features enable neurons to perform different functions:

  1. Sensory neurons carry afferent (incoming) information from the body into the spinal cord and brain.
  2. Interneurons integrate sensory and motor information within the central nervous system.
  3. Motor neurons carry efferent (outgoing) information from the brain and spinal cord to muscles.

In this activity you will get some hands-on experience with the various structural features of a neuron and how they impact its function by manipulating these features as you build your own neuron.

1.5 Step 1: Select the Type of Neuron

Step 1: Select the Type of Neuron
Continue

Question

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true
true
true
true
{qqMC1 === 0} setModel("selectedNeuronType", "sensory neuron")
{qqMC1 === 1} setModel("selectedNeuronType", "interneuron")
{qqMC1 === 2} setModel("selectedNeuronType", "motor neuron")

1.6 Step 2: Select the Structural Features of Your Neuron

Step 2: Select the Structural Features of Your Neuron

model.selectedNeuronType === "sensory neuron"

Sensory Neuron: A neuron that carries afferent (incoming) information from the body into the spinal cord and brain.

You have selected Sensory Neuron. Now choose the structural features from the options below that will enable your neuron to carry out its intended function. After you finish, you’ll test your neuron to see if your choices are compatible with your neuron’s functions.

model.selectedNeuronType === "interneuron"

Interneuron: A neuron that integrates sensory and motor information within the central nervous system.

You have selected Interneuron. Now choose the structural features from the options below that will enable your neuron to carry out its intended function. After you finish, you’ll test your neuron to see if your choices are compatible with your neuron’s functions.

model.selectedNeuronType === "motor neuron"

Motor Neuron: A neuron that carries efferent (outgoing) information from the brain and spinal cord to muscles.

You have selected Motor Neuron. Now choose the structural features from the options below that will enable your neuron to carry out its intended function. After you finish, you’ll test your neuron to see if your choices are compatible with your neuron’s functions.

Question

DHo9rDc2UMIfer+/5VhKdndi8jRoXtV4QoZDH5RezbSrSSh16wJn6CTcuHDYhAyoHYYMBHhIp+Wx9LDwHki1u0OI2Clyx1PCu445n6gUOZ4QVAf7V5wuI/0sm/Ti49f7EKyGGxSv3GmULlWs2UXN00rs4X4xscuxff1vWovA1NWUO6SCqHC6oQXI6O/XCfKsZRwiT+Lkcfont0PFxY/RAWge5gVxhOgPrGbAJ7MfBAnBD0UPmevgMcpZQP7y82Uq
true
true
true
true
true
{qqMC1 === 0} setModel("dendritesNumber", 1)
{qqMC1 === 1} setModel("dendritesNumber", 10)
{qqMC1 === 2} setModel("dendritesNumber", 20)

Question

vbT5eb420+v3NRgf15Tp6CoG4RtXjgI9Zfbqho8a6tnPqTrhjKGfWhdFXArOsSKLK1SlOe95+CF/iUGXHqdDqu13YbLamvV9DMtF3IrFe5lHSQqU6fl+VH8C82AjqImXRDmGDiadPq0LdLcjnX69OzHuPNFkxVmdMLd/MHx5qZ8QAtbWA6N/k3aZYi11dXRTgPuPKZz5Rnr8lyyGYA/8uUVJR0r+KXLYfFRCr4jdI2wZsRiYw3F6ej+WbUbF0i6SjNoJ+YXMdIQ0ZsbJlXTHFHsgJr/0ZluR
true
true
true
true
true
{qqMC1 === 0} setModel("dendriticBrachningLevel", "low")
{qqMC1 === 1} setModel("dendriticBrachningLevel", "medium")
{qqMC1 === 2} setModel("dendriticBrachningLevel", "high")

Question

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true
true
true
true
true
{qqMC1 === 0} setModel("axonLength", "short")
{qqMC1 === 1} setModel("axonLength", "long")

Question

IflNggz3THkpXM3JEo2axaZLyi0PdssbgaTqmep1RNsojOSp6iKBXu9big49KvKTU9Z4CY0wf9cJzAxdtbVhmvw63Tc/Z1dSz5z5nUwB1drHvM4mlfEX8M2GmZ3cAl5EhgvwN+QR3/gmOXfYdGRzqsREKtqxz6c963jrpUL2BpmjPPBI8luZfAZTf+xCuSYHRQ01+LhCsnZYnGAO5L/HJTYB4dgmOzeXEy7/Z1woEVvB/lu9RXRE+caebHg=
true
true
true
true
true
{qqMC1 === 0} setModel("axonCollateralsLevel", 0)
{qqMC1 === 1} setModel("axonCollateralsLevel", 1)

Question

L4nEadLWgo4xr2QYFM1ajKzlill+Kf6/LQ3l31Jto4pvZHmTwLxMgPNpXjyZbqbHewDIvRBMXptniXEYFyGq6IXyNh1APfs5mtG942l/03U79I9asG/eIbObkRGA7U9Pp0cTLwKlrX5RlMSOHJ1xU87fpfVBynp1pnNGjX9/dbpVrWGwNW1EuUJmK4DF3u//Z34qvZQ7LhKJeRMrOf9fSAoCG1BEhPL9tkIsU+97uGak0Xx9FpTmvpEapa6+VadhY/xyAw==
true
true
true
true
true
{qqMC1 === 0} setModel("terminalBrachningLevel", "low")
{qqMC1 === 1} setModel("terminalBrachningLevel", "high")

1.7 Neuronal Function

Neuronal Function
Test your neuron

Before we test your neuron, let’s review how structural features of a neuron impact its function.

Question

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All of your answers are incorrect. Please, review the feedback for each question.
At least one of your answers in incorrect. Please, review the feedback for each question.
All of your answers are correct! Please, review the feedback for each question.

1.8 Test your neuron

Test your neuron
Continue

model.selectedNeuronType === "sensory neuron"

Sensory Neurons

Two examples of sensory neurons: bipolar neuron of the retina and somatosensory neuron of skin or muscle. The first has one short dendrite which hardly branches and one short axon. The second has one long dendrite and one long axon, both branching a little

model.selectedNeuronType === "interneuron"

Interneurons

Neuron with multiple highly branching dendrites.
Stellate cell (thalamus)
Neuron with one long unbranching axon and several long branching dendrites.
Pyramidal cell (cortex)
Neuron with one long unbranching axon and multiple highly branched dendrites.
Purkinje cell (cerebellum)

model.selectedNeuronType === "motor neuron"

Motor Neurons

A neuron which has one long unbranched axon and several extensively branched dendrites.
Structural Features Your Neuron

model.selectedNeuronType === "sensory neuron"
Sensory Neuron

model.selectedNeuronType === "interneuron"
Interneuron

model.selectedNeuronType === "motor neuron"
Motor Neuron
Number of Dendrites

model.dendritesNumber === 1

1

A neuron with the only dendrite.

model.dendritesNumber === 10

10

A neuron with about 10 dendrites.

model.dendritesNumber === 20

20

A neuron with about 20 dendrites.

model.selectedNeuronType === "sensory neuron"

1

A neuron with the only dendrite.

model.selectedNeuronType === "interneuron" || model.selectedNeuronType === "motor neuron"

Can be 10 or 20

A neuron with about 10 dendrites.
A neuron with about 20 dendrites.
Dendritic Branching

model.dendriticBrachningLevel === "low"

low

A neuron with the only dendrite.

model.dendriticBrachningLevel === "medium"

medium

A neuron with about 10 dendrites.

model.dendriticBrachningLevel === "high"

high

A neuron with a high level of dendrite branching.

model.selectedNeuronType === "sensory neuron"

Can be low or medium

A neuron with the only dendrite.
A neuron with about 10 dendrites.

model.selectedNeuronType === "interneuron" || model.selectedNeuronType === "motor neuron"

Can be medium or high

A neuron with about 10 dendrites.
A neuron with a high level of dendrite branching.
Axon Length

model.axonLength === "short"

short

An axon of a short length.

model.axonLength === "long"

long

An axon of a long length.

model.selectedNeuronType === "sensory neuron" || model.selectedNeuronType === "interneuron"

Can be short or long

An axon of a short length.
An axon of a long length.

model.selectedNeuronType === "motor neuron"

Long

An axon of a long length.
Axon Collateral

model.axonCollateralsLevel === 0

0

An axon without collaterals.

model.axonCollateralsLevel === 1

1

An axon with one collateral.

model.selectedNeuronType === "sensory neuron"

0

An axon without collaterals.

model.selectedNeuronType === "interneuron" || model.selectedNeuronType === "motor neuron"

Can be 0 or 1

An axon without collaterals.
An axon with one collateral.
Terminal Branching

model.terminalBrachningLevel === "low"

low

An axon with a low level of terminal branching.

model.terminalBrachningLevel === "high"

high

An axon with a high level of terminal branching.

model.selectedNeuronType === "sensory neuron"

Low

An axon with a low level of terminal branching.

model.selectedNeuronType === "interneuron" || model.selectedNeuronType === "motor neuron"

Can be low or high

An axon with a low level of terminal branching.
An axon with a high level of terminal branching.

model.selectedNeuronType === "sensory neuron"

A single dendrite, with little or no branching, enables sensory neurons to carry afferent (incoming) information from specific sensory receptors to the spinal cord and brain. These neurons generally do not integrate information from multiple sources, which reduces mixing and optimizes the acuity (sharpness or clarity) of sensory input. Bipolar neurons in the retina, for example, use a single, sparsely branched dendrite to communicate highly specific light information from a distinct area of the retina to specific neurons in the visual system, resulting in high visual acuity. Somatosensory neurons have a single, sparsely branched dendrite that connects directly to a long axon, enabling it to carry touch information from specific areas of skin and muscle across relatively large distances to the spinal cord.

Sensory neurons generally do not integrate information from multiple sources or send information to multiple targets. A neuron with multiple dendrites and/or highly branched dendrites would receive and integrate information from multiple sources. A neuron with an axon that divides into multiple collaterals and/or has extensive terminal branching would send information to a variety of targets.

model.selectedNeuronType === "interneuron"

Numerous, extensively branched dendrites enable interneurons to gather and integrate sensory and motor information from a variety of sources within the central nervous system. A short axon would allow the neuron to communicate this information to other cells within the same brain area. Stellate cells, for example, are small, star-shaped interneurons with many, highly branched dendrites and a short axon, that integrate sensory information within the thalamus. A long axon would allow the neuron to communicate this information to long distance targets within the nervous system. Pyramidal cells, for example, are interneurons with a number of branched dendrites that gather and integrate information in the cortex, and a long axon which carries information over a relatively long distance, from the cortex to other parts of the brain and spinal cord.

Interneurons gather and integrate sensory and motor information and communicate that information to other cells within the same brain area or to distant areas of the nervous system. A single dendrite and/or sparsely branched dendrites would limit the ability of a neuron to receive and integrate information from multiple sources.

model.selectedNeuronType === "motor neuron"

Numerous, extensively branched dendrites enable motor neurons to gather and integrate efferent (outgoing) neural information from many sources. A long axon allows motor neurons to send this information over great distances, such as from the lower brainstem and spinal cord to muscles.

Motor neurons gather and integrate efferent (outgoing) neural information from many sources and send this information over great distances, from the brain and spinal cord to muscles. A single dendrite and/or sparsely branched dendrites would limit the ability of a neuron to receive and integrate information from multiple sources. A short axon would not allow a neuron to send information over long distances.

If you want to keep practicing, try building a new neuron by going back to

1.9 Summary of Neuron Structure

Summary of Neuron Structure
Finish

You have seen how the various structures impact the functionality of your neuron. Here is a brief summary of how these features impact all three types of neurons.

Two examples of sensory neurons: bipolar neuron of the retina and somatosensory neuron of skin or muscle. The first has one short dendrite which hardly branches and one short axon. The second has one long dendrite and one long axon, both branching a little

Sensory Neurons

A single dendrite, with little or no branching, enables sensory neurons to carry afferent (incoming) information from specific sensory receptors to the spinal cord and brain. These neurons generally do not integrate information from multiple sources, which reduces mixing and optimizes the acuity (sharpness or clarity) of sensory input. A bipolar neurons in the retina, for example, use a single, sparsely branched dendrite to communicate highly specific light information from a distinct area of the retina to specific neurons in the visual system, resulting in high visual acuity. Somatosensory neurons have a single, sparsely branched dendrite that connects directly to a long axon, enabling it to carry touch information from specific areas of skin and muscle across relatively large distances to the spinal cord.

Three examples of interneurons: stellate cell of the thalamus, pyramidal cell of the cortex and Purkinje cell of the cerebellum. The first has multiple highly branching dendrites. The second has one long unbranching axon and several long branching dendrites. The third has one long unbranching axon and multiple highly branched dendrites.

Interneurons

Numerous, extensively branched dendrites enable interneurons to gather and integrate sensory and motor information from a variety of sources within the central nervous system. A short axon would allow the neuron to communicate this information to other cells within the same brain area. Stellate cells, for example, are small, star-shaped interneurons with many, highly branched dendrites and a short axon, that integrate sensory information within the thalamus. A long axon would allow the neuron to communicate this information to long-distance targets within the nervous system. Pyramidal cells, for example, are interneurons with a number of branched dendrites that gather and integrate information in the cortex, and a long axon that carries information over a relatively long distance, from the cortex to other parts of the brain and spinal cord.

An example of motor neurons: motor neuron of the spinal cord. It has one long unbranched axon and several extensively branched dendrites.

Motor Neurons

Numerous, extensively branched dendrites enable motor neurons to gather and integrate efferent (outgoing) neural information from many sources. A long axon allows motor neurons to send this information over great distances, such as from the lower brainstem and spinal cord to muscles.

1.10 Summary

Summary
Take the quiz

Congratulations! You successfully completed the Build a Neuron activity. In this activity, you reviewed the major components of a neuron and their functions, the different types of neurons, and the way in which the physical structure of a neuron affects its function.

Your instructor may now have you take a short quiz about this activity. Good luck!

Question

q6XWQJflWtVkaFwYK6NEneWW7Y2E1zzqMCTXSg==
true
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