Structure and Function of Neuron

In this neurology article we'll look at the neuron the neurons are the communication cells they receive signals what you see smell here is thanks to a group of sensory neurons  also send out signals or information when we move our hands. Every time we breathe is because of commands being sent via efferent neurons so neurons are a big deal and because of this we have billions of neurons in our body.

Neurons

Structure of a neuron:

Here is a typical structure of a neuron it consists of dendrites which receive an information a signal the cell body, the soma, the axon hillock, the axon where information or the signal in a form of an impulse is propagated through .

Myelin:

There can be myelin which wraps around the axon to help an installation and speeding up the impulse and all the impulse will end at the synaptic terminal.

Where the impulse the information is passed on to a target cell so looking at it an input signal is received by the dendrites gets passed on to the cell body for integration and then the output signal is released from the synaptic terminal to a target cell for a specific response a desired effect responds the target cell.

Another Neuron:

In this case is another neuron but this neuron is different in that it is an unrelated neuron it has no myelin sheath wrapping around it this means that the propagation of the impulse along the axon is much slower .

Benefit of Myelin Sheath:

When you have a neuron with myelin sheaths the impulse travels much faster but now you might ask be asking yourself how is the information for one cell from a neuron is passed on to another cell?

Transmission of Impulse ( Synapsis ):

Well let's zoom into this area here where these two cells are close to each other where they synapse with each other here we have part of the synaptic terminal of the first neuron and it's presynaptic membrane . Here is part of the dendrite of the second neuron and it's postsynaptic membrane.

Synaptic Cleft:

The gap between the first and second neuron is known as a synaptic cleft . In the ends of this in the ends of the synaptic terminal region like here we find many mitochondria and vesicles containing what's called neurotransmitters . 

Neurotransmitters:

These neurotransmitters are released for communication for the communication process between cells. What happens is that when a signal arrives at the dendrites of the neuron it will create an impulse that will carry this information and propagate it towards the terminal this impulse is an action potential.  

Purpose of Action Potential:

The action potential will cause once it arrives at the terminal synaptic terminal it will cause the vesicles here to release the neurotransmitters into the synaptic cleft where the neurotransmitters will then bind onto the cell's postsynaptic membrane so we can say that the synapse is the site for intracellular communication . 

Input and Output Signals:

And seeing that the postsynaptic membrane of the postsynaptic cell belongs to the dendrite of a neuron it will receive this information and then create a net another action potential that will propagate along the axon towards the synaptic terminal . 

So our new input signal is received by the dendrites will be integrated in the soma and then and then it will the information the action potential the information will pass along the axon towards the terminal and will be passed on as an output signal via neural.

Target:

Is that will target a particular cell it can be a neuron again or it can be a muscle cell or an endocrine cell . 

How signals are being passed all around our body:

Any kind of cell depending on where the neuron is located and what its desired response wants to be  what effect it wants to cause so now that we have an idea of how signals are being passed all around our body and how we receive signals all around our body . 

Soma or Cell Body:

Let's learn more about the soma of a neuron and how the neurotransmitters are packaged up are made so here we have a close-up of the soma of the neuron we have the nucleus containing the genetic material , the rough endoplasmic reticulum around it with bound ribosomes and free ribosomes for protein synthesis .We have the Golgi apparatus for packaging and we have the lysosome. 

Synthesis of neurotransmitter:

Now the protein neurotransmitters are synthesized in the rough endoplasmic reticulum by ribosomes and then packaged up by the Golgi apparatus.

So here we have the rough endoplasmic reticulum synthesizing new neurotransmitters that passes them on to the golgi that will then package them up in vesicles . These vesicles containing your transmitters from the golgi are then brought to the synaptic terminal. 

Synaptic Bulb:

Here we have this synaptic bulb of the synaptic terminal so these vesicles containing the neurotransmitters and also our mitochondria they move down via micro filaments or micro tubules and they move to the terminal bulb here the vesicles are in the synaptic bulb where they can be released via exocytosis to the synaptic cleft.

Recycling of Vesicles:

When an action potential arrives the neurotransmitters can be reabsorbed in the synaptic cleft and form vesicles and then these vesicles can be recycled they can travel back to the soma of the neuron where they were fused with license the lysosomes will digest these vesicles for recycling so neurons are a big deal.

Neuron Structure

What we just talked about for us cellular communication for sending out signals and also receiving signals receiving information .These neurons are I just drew is actually a typical structure or typical shape of a specific type of neuron. 

Efferent semantic neuron :

An efferent semantic neuron that is however there are a few types of structures neurons can be categorized into and these structural categories it can be determined by which part of the nervous system the neurons belong to if that made any sense I'll just draw a diagram to explain .

Division of Nervous System

This so the nervous system remember it can be divided into two major parts that is the central nervous system and the peripheral nervous system. 

Now I drew two peripheral nervous systems because the peripheral nervous system consists of a sensory division and a motor division or better yet an efferent division the sensory division of the peripheral nervous system consists of sensory neurons that look something like this it has dendritic branches.

Unipolar neuron:

Here the axon on either side of the soma the cell body and then the synaptic terminal. Here this type of neuron is categorized under the structure of a unipolar neuron . 

Bipolar Neuron:

Now we also have another type of sensory neuron which is slightly similar in that it also consists of dendritic branches but the dendrite will extend to the soma then we have the axon and finally the synaptic terminal this type of neuron is categorized under the structure of a bipolar neuron  . 

Inter neuron:

As you can see the unipolar and bipolar neuron are only slightly different the bipolar neuron we have two separate processes separated by the cell body so we have the dendrite and then the axon on one end the central nervous system consists of many interneurons .

Interneurons you can say our neurons that bring signals within the central nervous system so from the brain to the spinal cord.

Inter neuron as Glial Cells:

For example but we also have inter neurons that act as glial cells , helper cells .Anyway these inter neurons have some completely different structures to other neurons . 

An example of an inter neuron is this what I'm drawing and it doesn't look like it has an axon but only has a cell body in the center with many dendritic branches around it this type of a neuron is categorized under the structure of an electronic neuron .

Then we have a multipolar neuron type which contains dendritic branches on one end and then straight away in an axon terminal branch on the other separated by the cell body . Some multipolar neurons on in the central nervous system look slightly different than this and we shall soon see what I am talking about.

With or without Myelin Sheath:

Now the effort division of the peripheral nervous system contains efferent neurons ,motor neurons which are all multipolar and structure. We can have efferent neurons with myelin wrapping around it or we can have efferent neurons without myelin wrapping around it either way both are multipolar in structure in that it consists of dendritic branches and then we have the cell body and then the axon and terminal branches.