017 Two Types of Receptors

017 Two Types of Receptors

Leslie Samuel IBTV, The Nervous System 161 Comments

After neurotransmitters are released from the cell, they bind to receptors on the next cell.

In this video, Leslie explains how the two different types of receptors – the ionotropic and metabotropic receptors – work to bring about various responses in the cell.

Enjoy!

Transcript of Today’s Episode

Hello and welcome to Interactive Biology TV, where we’re making biology fun! My name is Leslie Samuel. In this episode, Episode 17, I’m going to be talking about 2 types of receptors. We’ve been talking about the nervous system, we’ve been looking at neurons, and we’ve seen how the action potential starts at the axon hillock, the signal travels all the way down the axon, down to the axon terminals. In Episode 16, we looked at how the neurotransmitters are released from the axon terminals, and they bind to receptors on the next cell.

What we’re going to be doing is looking at those receptors because there are 2 basic types of receptors:
1. Ionotropic
2. Metabotropic

What we’re going to do is we’re going to look at the ionotropic receptors first. With ionotropic, these are very fast-acting receptors. What I’m going to do is I’m going to attempt to draw one now. Let’s say here we have a receptor, and this is a cell membrane. We have the signal that comes along the axon of the preceding cell, and it releases neurotransmitters. I’m going to say these little dots here are neurotransmitters, and they’re in the synaptic cleft.

What’s going to happen if it’s an ionotropic receptor, the neurotransmitter is going to come and it’s going to bind to the receptor. The way these receptors are set up is relatively simple. When the neurotransmitter binds to the receptor, that causes the channel to open. So, I’m going to draw this showing that now there’s an open space. And then, if there are ions that are outside the cell that are specific to that channel, those ions can then enter the cell. So it’s very fast-acting. The neurotransmitter binds to the receptor, and then the channel opens so that the ions can travel inside the cell. Once again, these are ionotropic receptors.

Now, of course, there are going to be different types of neurotransmitters and different types of receptors that are going to act in this way. I’m going to take the example of acetylcholine as a neurotransmitter. So we’re going to start with ACh, and that’s for acetylcholine. We’re going to call these neurotransmitters acetylcholine, and the receptor that’s the ionotropic receptor for acetylcholine is called the nicotinic receptor. The reason it’s called nicotinic is because this is the receptor that nicotine acts on, and we’re going to talk about that in a later episode.

So, acetylcholine comes, and actually 2 acetylcholines bind to the nicotinic receptor, and then that causes sodium ions to rush in. And now you know that sodium ions are going to have a positive charge, so what do you think that’s going to do to the membrane of the cell? Well, of course, that’s going to make it more positive. So I’m going to look at it here. Let’s say I’m looking at voltage or membrane potential on the Y-axis, and I’m going to have time on the X-axis. This is the resting membrane potential.

When something like this happens that causes sodium to come in, that can cause the membrane potential to get this little bump here. So it increases a little from that sodium rushing into the cell. Because this is becoming more positive, we’re going to call this an excitatory (it’s getting it excited) post-synaptic potential. EPSP, excitatory post-synaptic potential. Because it’s acetylcholine binding to the nicotinic receptor, that’s going to cause sodium ions to rush in, causing an excitatory post-synaptic potential.

Now, there’s another type of neurotransmitter, 2 examples would be GABA and glycine (forgive my writing there, but I think you get it.) When these bind, let’s say this is GABA or glycine, what that is going to do is it’s not going to cause not sodium ions, but chloride ions, and let’s say this is chloride, Cl-, to rush into the cell.

If a negative ion rushes into the cell, what is that going to do? Well, you probably guessed it. Instead of causing an excitatory post-synaptic potential, that’s going to cause an inhibitory post-synaptic potential, or an IPSP. So if it’s a positive ion rushing in, you get an EPSP. If it’s a negative ion rushing in, you’re going to get an IPSP. This is a really fast-acting process: neurotransmitter binds, channel opens, ion rushes in.

Let’s go to the next type of receptor, and that’s called the metabotropic receptor. This is going to be a little more complicated, because what we have here, just like before, we have a receptor in the membrane. And just like before, we have neurotransmitters that are outside the cell. But what’s different here, is that inside the cell, associated with this receptor, we have a G protein.

What happens is this neurotransmitter comes and it binds to the cell, just like before, and instead of opening a channel, what that does is it activates the G protein. And then this G protein then goes on to activate a second messenger system where there can be multiple processes that are happening, causing a certain response on the inside of the cell.

So this is a slower process in that there are multiple processes happening, and it causes a different type of response. That response can be a number of different things, and we’re going to talk about that a little later.

An example of a metabotropic receptor would be the muscarinic receptor. With the muscarinic receptor, acetylcholine is still the neurotransmitter, so ACh, and that binds to the receptor that activates a G protein. When it activates a G protein, a number of processes happen that cause multiple responses, depending on the type of muscarinic receptor we’re dealing with. One of the features that we have here is for every neurotransmitter that binds, that can activate a G protein, and whatever process this is can happen multiple times, and then this process this is can happen multiple times, so that we get a greater response on the inside.

For example, I’m just going to take a random number. Let’s say here we activate 1 G protein, and this process can happen 10 times, and each one of those can cause this next process to happen 10 times. So this second messenger system can result in a significant amount of amplification, so that we can get a significantly greater response.

Those are the 2 types of receptors: we have the nicotinic receptor and we have the muscarinic receptor. If you have any questions about this, you can leave them in the comment section below, or you can just leave a comment letting me know what you think about the format of what I’m doing, and even give suggestions for future episodes. That’s it for this video, and I’ll see you on the next one.

199 comments
Alan isaac
Alan isaac

Are these receptors and channels actually seen by microscope or is this hypothetical concepts

Maha Khan
Maha Khan

kindly also provide authentic refreneces (from research articles/books)

kamikazeicecream
kamikazeicecream

This is because the IPSP or EPSP we are talking about is on ANOTHER neuron across the synaptic cleft (space). You are right about the refractory period though, just that we are talking about two neurons here, not just one.

Dikshhya Acharya
Dikshhya Acharya

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lina mateeva
lina mateeva

ok I'm studding bio psychology and for the first time it actually made sense!!! I only wish i found these tutorials sooner bf my test:))))thank you, thank you, thank you!

smilebeautifulworld
smilebeautifulworld

Thank you that's such a good explanation :) but i have one question .. we have learned that a.p have a property of one way propagation.. so the post synaptic cant receive an a.p if it's already excited.. right? also the ipsp is also to stabilize the membrane rather then to hypopolarize.. So the question is.. how does the the ipsp stabilizes already excited membrane? I mean the only way for the neuron to recieve a second potential is to be in refractory period .. Hope you understood my confusion.

Kellie Tunney
Kellie Tunney

Thank you so much! Watched a 50 minute lecture... made no sense. Watched this along with your synapse video and it's so clear! Keep the physiology videos coming!

haron11
haron11

is it only acetycholine that acts on muscarine and nicotine receptors or can other transmittors act on them as well?

Sophia Loaiza
Sophia Loaiza

You make it so easy to understand! So thankful for interactive biology tv. It makes me look like a genius

Carolyn Foster
Carolyn Foster

Great videos :D find I'm learning things so much easier and understanding so much better when I can listen to you explain and watch you illustrate each step of a process; a million times better than just reading through pages and pages of text!

learningabhi
learningabhi

Thanks. You make things easy to understand. Please upload more videos like this.

Linda Holder
Linda Holder

I wanted to find out if you block a muscarinic receptor what will happen? I am studying neuroleptic medications and trying to understand the way these work. I am not sure you can help, but anything would be appreciated. Thanks

noyheimann
noyheimann

do you use wacom stylus or n-trig? anyways, thanks a lot - I understand things better now :)

Kloszewska
Kloszewska

I am in an advanced brain anatomy class in my Psychology major... I do understand a lot but your videos are GREAT for the visual understanding part of it. Thank you so much! :D

Hannah Murphy
Hannah Murphy

Thank you so much :-) In my exam yesterday i had an essay on the three stages of chemical signaling and your videos helped so much :-)

Jack Rose
Jack Rose

Seriously helped me grasp these concepts! You break it all down so easily and clear :)

TheJennieration
TheJennieration

you are easily 10 billion times better than my lecturer!

hunger4jsutice
hunger4jsutice

Once again, a wonderful, clear, concise explanation that changes learning from wrote memorization to understanding and long term retention. You are one of the reasons I am getting As in Anatomy and Physiology. THANK YOU!!!!

Josef Shivute
Josef Shivute

wow this is really awesome.....i watch ur videos to understand topics i dnt understand in my physiology class..thank u very much

hadasdel
hadasdel

what happens after that? how does the reuptake works? I have an exam on friday and so far your videos are the only thing that helps me :)

Yogesh Subedi
Yogesh Subedi

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megan giannino
megan giannino

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Gabrielle Fillion-Bertrand
Gabrielle Fillion-Bertrand

Thank you very much for your good explanations. I speak French and your language is easy to understand. It is clear and concise. Keep it up.

Jae Young Kim
Jae Young Kim

Oh my God Thank you so much Leslie you really wouldn't understand how much help I got from this 10 min clip... THANK YOU!!

Ferny Cabral
Ferny Cabral

Is K+ important in the second messenger system?

chocolateddy22
chocolateddy22

wow....that makes soooo much more sense now!! thank you!!! (if I pass my exam it'll be thanks to you!!)

Ndunaija
Ndunaija

You are my physiology HERO. I feel more confident about the course now that I have you around. You are an amazing instructor.

Bickity Banks
Bickity Banks

Thank you very much for posting this series of videos! I am LEARNING a lot from them. You explain everything clearly and concisely. Seriously, my grades are improving because of your videos.

Younness Dehbi
Younness Dehbi

Well Sir, I'm a nursing student, and I it took 8 hours to explain what you just explained in 9 min, THANK YOU VERY MUCH

Stefanie Gill
Stefanie Gill

Thank you! This was great, as most others will agree! I will definitely be watching the other videos!!

Bosele Pebe
Bosele Pebe

You should have explained what happens once G-protein is activated, through to synthesis of cAMP till kinase action.. Thats where its a bit tricky..

chen582
chen582

it was so helpfull!! my language is not English but steel it was so easy to me to understand it! so, thank you so much for this!!

camandbex
camandbex

Explained so simply!! A million thank yous!!!

Anup Shetty
Anup Shetty

Thanks a lot... You make my pharmacy course 10 times easier... thank you again :)

Lamees Awwad
Lamees Awwad

I'm a 1st year med student and you couldn't have explained the process more beautifully .. This has been helpful !! Thank you so much!!!

1AlleyC
1AlleyC

Awesome....I am a 1st year med student and you have explain it best......