Nervous Tissue: The Neuron - Online Tutor, Practice Problems & Exam Prep

A neuron consists of three main parts: dendrites, the cell body (soma), and the axon. Dendrites receive incoming electrical signals, while the axon conducts outgoing signals, often extending several feet. The cell body houses the nucleus and organelles. Understanding the flow of electrical impulses—entering through dendrites and exiting via the axon—is crucial for grasping neuronal function. This process is essential for communication within the nervous system, impacting everything from reflexes to muscle contractions.

The Neuron

In this video, we're going to begin our lesson on the neuron, more specifically focusing on the structure of the neuron. Recall from our previous lesson videos that the primary cell of the nervous tissue is the neuron, and it is responsible for generating and conducting electrical impulses. A neuron has 3 basic structural parts. The first is the dendrites, the second is the cell body or the soma.

The third is the axon. The dendrites are extensions that lead into the cell body and are responsible for receiving incoming electrical signals. The cell body or the soma contains the nucleus of the cell and most of the organelles of the cell as well. Lastly, the axon is a long thin portion of the neuron that conducts outgoing electrical signals. I want to emphasize that axons can be pretty long, several feet in some cases.

That's really long for a single cell. Notice below, we have a short memory tool to help you remember that the dendrites receive the incoming signals, whereas the axon transmits or conducts the outgoing signals. The memory tool states that signals enter via the dendrites, with an emphasis on the "en" in enter and the "en" in dendrites. The axon takes the signal away; you can think "a" in axon is for "a" in away.

Let's take a look at our example image below, where we can label the three parts of the neuron and indicate the direction of an electrical impulse traveling through the cell. Notice the neuron toward the top, where these extensions leading into the cell body, which are the dendrites. The dendrites receive the incoming signal, thus the signal enters via the dendrites. The cell body or the soma contains the nucleus of the cell and most of the organelles.

The long portion of the neuron below is the axon. The axon is a long thin portion of the neuron that conducts outgoing electrical signals. If we wanted to trace the path of an electrical signal, we could use a red color. The electrical signal is received by the dendrites. The electrical signal starts in the dendrites, is conducted through the cell body, moves into the axon, and moves in this direction. Therefore, the axon conducts the outgoing signal. This is the direction of the electrical impulse traveling through the cell, starting in the dendrites, moving through the cell body, then through the axon as an outgoing signal to be transmitted to the next neighboring neuron or a muscle cell, for example.

This concludes our brief lesson on the neuron, and we'll be able to get some practice moving forward. So, I'll see you all in our next video.

Which of the following is the most likely path of an electrical signal travelling through a neuron and arriving at a muscle?

• A. Neuroglia → dendrites → a cell body → axon → muscle.
• B. Dendrites → cell body → axon → muscle.
• C. Dendrites → axon → cell body → muscle.
• D. Axon → cell body → dendrites → muscle.

Practice 2

So here we have a practice problem that's asking, how does the axon structure reflect its function? And we've got these four potential answer options down below. Recall from our previous lesson videos that the axon is a long and thin portion that extends off of the cell body or the soma of the neuron and it's going to be carrying outgoing electrical signals. Just based on the fact that we know axons are going to be long and thin, we can eliminate some of these answer options here. Notice that answer option d says that the axons are always short so that electrical impulses can travel through it quickly. But again, we know that this is not going to be the case. Axons tend to be long, and in some cases, they can be several feet long, making neurons the longest cells in the human body. So to say that axons are always short is simply not going to be correct, and that's why we can eliminate answer option d. Now notice answer option c says that the axons are thick in order to self-regulate. But once again, we know that axons tend to be thin. So, to say that axons are thick is not going to be correct. Therefore, we can eliminate option c. We are now between either option a or option b. Notice that option b says that the axon is tough in order to protect itself from damage. But we know this is not going to be the case; we know that axons and neurons, in general, are pretty delicate cells. This is why the neurons rely on neuroglia or glial cells to provide support and protection. So, to say that the axon is going to be tough, again, is not going to be correct, so we can eliminate option b. So, of course, this leaves answer option a as the correct answer, which says that axons can be long so that they can carry electrical signals long distances. Once again, we know that axons tend to be long. In some cases, they can be several feet long, again making neurons the longest cells in the human body. So once again, option a here is the correct answer, and that concludes this practice. I'll see you all in the next video.

Here’s what students ask on this topic:

What are the main parts of a neuron and their functions?

A neuron consists of three main parts: dendrites, the cell body (soma), and the axon. Dendrites are extensions that receive incoming electrical signals. The cell body, or soma, contains the nucleus and most of the cell's organelles, playing a crucial role in maintaining cell function. The axon is a long, thin structure that conducts outgoing electrical signals, which can travel several feet in some cases. Understanding these parts and their functions is essential for grasping how neurons communicate within the nervous system, impacting everything from reflexes to muscle contractions.

How do electrical impulses travel through a neuron?

Electrical impulses in a neuron travel in a specific direction. They start at the dendrites, which receive the incoming signals. The impulse then moves through the cell body (soma), where the nucleus and organelles are located. Finally, the impulse travels down the axon, which conducts the outgoing signal to the next neuron or a target cell, such as a muscle cell. This directional flow—from dendrites to soma to axon—is crucial for effective communication within the nervous system.

What is the role of dendrites in a neuron?

Dendrites are extensions of the neuron that play a critical role in receiving incoming electrical signals. They lead into the cell body (soma) and are the first point of contact for these signals. By capturing and transmitting these signals to the soma, dendrites help initiate the process of neuronal communication. This function is essential for the neuron's ability to process and respond to information, impacting everything from sensory perception to motor control.

Why is the axon important in neuronal function?

The axon is crucial for neuronal function because it conducts outgoing electrical signals from the cell body (soma) to other neurons or target cells, such as muscle cells. This long, thin structure can extend several feet, allowing for the transmission of signals over long distances within the body. The axon's ability to efficiently conduct these signals is essential for communication within the nervous system, affecting processes like reflexes, muscle contractions, and overall coordination.

What is the significance of the cell body (soma) in a neuron?

The cell body, or soma, is significant because it houses the nucleus and most of the organelles of the neuron. This central part of the neuron is responsible for maintaining cell function and processing incoming signals received by the dendrites. The soma integrates these signals and plays a crucial role in generating the outgoing electrical impulse that travels down the axon. Understanding the soma's role is essential for comprehending how neurons function and communicate within the nervous system.