The Neuron
Summary
TLDRIn this educational video, Paul Andersen explains the neuron as the fundamental unit of the nervous system. He details the neuron's anatomy, including the cell body, dendrites, and axon, and how they facilitate the transmission of information via neurotransmitters and action potentials. He also discusses the myelin sheath's role in speeding up signal transmission and the structural and functional classifications of neurons, such as multipolar, bipolar, unipolar, and axonic neurons, as well as sensory, motor, and interneurons. The explanation aims to clarify the neuron's complexity and its crucial role in our body's response to environmental stimuli.
Takeaways
- 🧠 The neuron is the fundamental unit of the nervous system, responsible for receiving and transmitting information.
- 🐛 In simple animals like a nematode worm, the nervous system is composed of only 302 neurons, yet they are intricately connected.
- 🧬 Humans have approximately 100 billion neurons, most of which are located in the brain and spinal cord.
- 🏠 The cell body of a neuron is the central part, containing typical cellular structures like the nucleus and Golgi apparatus.
- 🌐 Dendrites are extensions from the cell body that receive information in the form of neurotransmitters from other neurons.
- 🚀 The axon is the part of the neuron responsible for transmitting information, starting at the axon hillock and extending to the terminals.
- 🔌 Synapses are the gaps between neurons where information is passed from one neuron to another.
- 🛡️ Myelin sheaths are insulating layers that wrap around some axons to facilitate faster transmission of signals.
- 🔍 Neurons can be classified structurally based on the number of poles or extensions coming from the cell body, such as multipolar, bipolar, unipolar, and axonic neurons.
- 🔬 Neurons are also classified functionally into sensory (afferent) neurons that bring information into the central nervous system, and motor (efferent) neurons that send information out to effectors like muscles and glands.
- 🔄 Interneurons are neurons that connect between sensory and motor neurons within the central nervous system, facilitating complex interactions.
Q & A
What is the basic unit of the nervous system?
-The basic unit of the nervous system is the neuron.
How many neurons does a simple animal like a nematode worm have?
-A nematode worm has approximately 302 neurons.
How many neurons are present in the human body?
-The human body contains about a hundred billion neurons.
What is the primary function of the cell body of a neuron?
-The cell body, or soma, is the metabolic center of the neuron, containing the nucleus and organelles like the Golgi apparatus and mitochondria.
What are dendrites and what is their role in a neuron?
-Dendrites are extensions of the neuron cell body that receive information in the form of neurotransmitters from other neurons.
What is the axon and what does it transmit?
-The axon is responsible for transmitting information away from the neuron. It begins at the axon hillock and moves toward the axon terminals.
What is an action potential and how does it relate to the neuron's function?
-An action potential is an electrical signal that travels along the neuron's axon, allowing the neuron to send information to the next neuron.
What is a Myelin sheath and how does it aid in the transmission of information in the axon?
-A Myelin sheath is a protective covering around some axons, made by Schwann cells, that insulates the nerve and allows information to travel more quickly.
What is the structural classification of neurons based on, and what are the common types?
-Neurons are structurally classified based on the number of poles or extensions coming off the cell body. Common types include multipolar, bipolar, unipolar, and axonic neurons.
What is the difference between sensory neurons and motor neurons in terms of their function?
-Sensory neurons, also known as afferent neurons, bring information into the central nervous system from the environment. Motor neurons, on the other hand, send information out to effectors such as muscles and glands.
What are inter neurons and what is their role in the nervous system?
-Inter neurons are neurons that make connections between sensory and motor neurons within the central nervous system, facilitating communication between different parts of the nervous system.
Outlines
🧠 Neuron Basics and Structure
Paul Andersen introduces the neuron as the fundamental unit of the nervous system, explaining its role in processing information from the environment. He contrasts the simplicity of a nematode worm's 302 neurons with the complexity of human's 100 billion neurons, mostly in the brain and spinal cord. The neuron's anatomy is detailed, including the cell body with its typical cellular components like the nucleus and mitochondria, and the extensions known as dendrites that receive neurotransmitters from other neurons. The axon's function in transmitting information is also discussed, highlighting the axon hillock and terminals, and the role of synapses in neuron-to-neuron communication. The importance of action potential in signal transmission is mentioned, with a reference to a related video for further details. Additionally, the role of myelin sheaths in insulating and speeding up signal transmission along axons is explained.
Mindmap
Keywords
💡Neuron
💡Nervous System
💡Cell Body
💡Dendrites
💡Axon
💡Action Potential
💡Myelin Sheath
💡Synapse
💡Structural Classification
💡Functional Classification
💡Interneurons
Highlights
Neurons are the basic unit of the nervous system, essential for receiving and responding to information from the environment.
A simple animal like a nematode worm has only 302 neurons, which allows for complex information processing.
Humans possess approximately 100 billion neurons, most of which are in the brain and spinal cord.
The cell body of a neuron, containing the nucleus and other organelles, is the center of metabolic activity.
Dendrites are extensions that receive information in the form of neurotransmitters from other neurons.
The axon is responsible for transmitting information, starting at the axon hillock and moving to the terminals.
Synapses are the gaps between neurons where information is passed on to the next neuron.
Action potentials are the mechanism by which neurons send information, detailed in a separate video.
Myelin sheaths insulate axons, allowing for faster transmission of information, and are produced by Schwann cells.
Nerve fibers are axons wrapped in myelin sheaths, facilitating rapid signal transmission.
Neurons can be classified structurally based on the number of poles or extensions coming off the cell body.
Multipolar neurons are the most common type, with multiple dendrites and a single axon.
Bipolar neurons are rare and transmit information from sensory receptors in the eyes and nose.
Unipolar neurons, also known as pseudo-unipolar in vertebrates, are sensory neurons that transmit information to the CNS.
Axonic neurons, found in the brain, are less understood and have no distinct axon.
Neurons can also be functionally classified as sensory, motor, or interneurons based on their role in information processing.
Sensory or afferent neurons bring information from the environment to the central nervous system.
Motor neurons transmit information from the CNS to effectors like muscles and glands.
Internurons facilitate connections between sensory and motor neurons within the CNS.
Transcripts
Hi, it's Paul, Andersen and in this video
I'm going to go over the basics of the neuron. The neuron is the basic unit in the nervous system. in a simple animal like
A nematode worm, they only have 302 neurons,
But what they allow them to do is to take information in from their surroundings and respond to that
Information. if you look at how those 302 neurons are connected it's very complex. Now humans are quite a bit bigger
And we have a hundred billion neurons in our body.
Most of those are centered in the central nervous system in the brain and the spinal Cord,
But the basic unit of our nervous system is the same: it's the neuron. If we look at the neuron
Anatomy and remove all the other neurons that the center is going to be what's called the cell body.
This is a typical cell. It's metabolizing. Cell. It's taking an energy
It's using that energy and so it's going to have a nucleus. It's going to have Golgi apparatus
Mitochondria, it's a typical cell but there are extensions of those cell bodies called the dendrites. Those dendrites are connected to other neurons
and they're taking information in in the form of neurotransmitters. In fact this whole side of the neuron is receiving information
We then have the axon the axon is where we're transmitting
Information it begins at the Axon hillock and is going to move to the terminals now remember the terminals
There's a synapse that connects us to other neurons, but the signal is going to move in this direction
We're taking in information from the dendrites the cell body, and then we can send information to the next neuron now
How do we do that is through an action potential and I have a video that
I'll put a link to where I go into the specifics of how that occurs
But certain axons in our body are really really long and for that information to travel quickly. We will wrap them in Myelin sheaths
It's a schwann Cell that's wrapped around it the way
It works is we put the voltage-gated channels in between that and it acts to insulate that nerve
It allows the information to travel more readily down that axon.
And, we generally say if you have an axon that's wrapped in Myelin sheath. We call that a nerve fiber inside our body now
We're taking in information as well
So there's going to be another neuron that's connected to both the cell body and the dendrites of that cell
But there's going to be a gap between these two and we call that a synapse
It's a connection between neurons. Again
I Have another video on the synapse if you want to dig into the specifics especially of how chemical synapses work neurons are classified in two
Ways first way is due to their structural classification, so if we take the cell body of a typical neuron
like this multipolar neuron
The way you can figure out what what type of a neuron is is?
Find the cell body and figure out how many poles are coming off of that cell body?
So if we count them, we have a number of different dendrites that are coming off of this neuron
And then we have at one axon that's coming off, and so we call that a multipolar neuron
This is the most common neuron that we have in our body if we look at the next one
We find the cell body again. How many poles do we have coming off of it?
We've got the axon coming out and the dendrite coming in and so we call this a bipolar neuron Bipolar Neurons are very rare
They transmit information from the receptors in our eye
receptors in our nose
If we look at the next one, here's the cell body you can see there's only one pole coming off of that
It's actually a fused axon and dendrite and we call that a unipolar neuron. Now in vertebrates
It's sometimes referred to as the pseudo uni-polar neuron these are going to be most of the sensory neurons in our body
They're taking information in and transmitting that back into the central nervous system
And then if we look on the next one if we look at that
You can see there's no axon on it as at all so we call that an Axonic neuron
These are found in the brain, and they're not super understood now there are a lot of other structural classifications
But these are the general ones that you're going to find in a typical anatomy class?
Now neurons can also be classified according to their functional classification those that take in information
stimulus coming in from our environment
And then the response that we have so if we kind of move that to the central nervous system
We're looking at a cross-section of the spine so we're taking information in from receptors
So these could be in the skin for example touch receptors heat receptors pain receptors
And so we have to transmit that information to the central nervous system. So those neurons that bring information in are
Sometimes refer to as sensory neurons or afferent neurons you can see this is a unipolar neuron
And it's transmitting that information into the central nervous system, and then we have information going back out
We're sending information out to effectors in our body: could be muscles, could be glands. And, we're going to call those motor neurons
They're moving away from the center
sometimes we refer to those as
afferent neurons as well now there should be connections between those neurons those aren't all the neurons we have in our body and so we
Also have these connections in the middle and those are going to be called inter neurons
And so that's the neuron
How did you do can you remember the different parts of the neuron do you remember that these are the dendrites the cell body?
Do you remember what type of a neuron this is if not go back and rewind it?
But those are neurons those are the basics, and I hope that was helpful
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