Synaptic Transmission | Neuron

hi everyone dr. Mike here now in previous videos have spoken about how we can either stimulate or inhibit a neuron from sending a signal we've spoken about how a neuron can actually send that signal that electrical impulse down its long axon we call that an action potential and now what we're going to talk about is what happens once that action potential has reached the very end of the neuron okay the synaptic terminal so what's happened just a very quickly recap is remember positive sodium was rushing into the cells via this sodium voltage-gated sodium channels when the positive sodium enters the neuron it makes that area of the neuron positive now remember at rest a neuron has a charge difference from inside compared to outside it's negative 70 millivolts inside compared to outside once the positive sodium moves in it brings that charge up from negative 70 to negative 65 to negative 60 and then when it hits negative 55 that's the threshold to open up all of these voltage-gated sodium channels so with this sodium coming in it makes it negative 55 it flips its lid the next sodium comes in and makes this area negative 55 as well remember so much sodium comes in that once it hits negative 55 all the voltage-gated sodium channels open up all the positive sodium comes in and it makes it extremely positive in that area of the neuron so what's happened now is all the sodium channels have opened up and we're at the end of the neuron it becomes so positive here at the end of the neuron that it stimulates a different type of voltage-gated channel it stimulates a Celt of voltage-gated calcium channel and so they start to flip their lids and open up we've got all this calcium outside calcium rushes into the cell now calcium is positively charged as well and what calcium does when it enters the synaptic terminals the very ends of neurons it stimulates these little things here which are called vesicles so their plasma membranes with neurotransmitters inside and it stimulates them to start moving their way towards the player the membrane they will fuse with the plasma membrane and release their contents which will be neurotransmitters now if they are excitatory neurotransmitters like glutamate for example they will cross or diffuse that synaptic cleft they will bind to their receptors on the next neuron this is the pre synaptic neuron thus the neuron pre or before the synapse this is the post synaptic neuron this neurotransmitter will bind to its receptor the receptor will open up a channel and allow for sodium to enter the neuron making it positive inside this neuron again remember it's negative 70 but all this positive sodium coming and it makes it positive if it hits negative 55 it then opens up the voltage-gated sodium channel and sodium comes in and then the whole action potential begins again so what you get is an electrical signal then a chemical signal then an electrical signal again and that's if you have a stimulatory neurotransmitter if you have an inhibitory neurotransmitter it's not going to open sodium channels it may open up chloride channels and negative chloride goes in if negative chloride goes in it makes it not positive but even more negative inside and stops an electrical signal from being sent because remember it needs to go from negative 70 to negative 55 if you put more negative things in or go from negative 70 maybe down to negative 75 negative 18 negative 85 negative 90 so that's hyper-polarization stopping in your own from sending a signal okay so what are the phases of synaptic transmission you have the action potential coming in with voltage-gated sodium channels enough sodium goes in that it stimulates voltage-gated calcium channels calcium comes in this stimulates these vesicles that contain your transmitters to fuse with the membrane and release their contents the neurotransmitters will diffuse across the synapse and bind to their receptors on the postsynaptic neuron if it's excitatory 'el open up sodium channels for sodium to come in and that stimulates the action potential again now this is for a neuron sometimes this neuron is going to sign apps with an organ sometimes it's going to sign ups with them hustle if it signups with a muscle that's called the neuromuscular Junction I'll do a entire video series on that and the neurotransmitter it releases is acetylcholine okay so all muscles need acetylcholine to stimulate it to open up sodium channels to stimulate the action potential for muscles to contract so that's synaptic transmission

Channel: Dr Matt & Dr Mike

Views: 149,846

Keywords: action potential, synaptic transmission, synapse, neurotransmitter, gaba, glutamate, excitatory neuron, inhibitory neuron

Id: fhiJo1QYGtA

Length: 4min 49sec (289 seconds)

Published: Tue Apr 02 2019