Class Notes (810,420)
Canada (494,121)
Psychology (3,457)
PSY260H1 (58)

Lecture #3 Notes (Non-associative learning) Topics: the process of neural firing, action potentials, the myelin sheath, spatial summation, temporal summation, process in the synapse, "Myshkin", facilitation, potentiation, titanic stimulation, LTP/LTD and,

11 Pages
Unlock Document

University of Toronto St. George
Martin Ralph

Lecture ThreeThe question we will focus on today is What is the system for the mechanistic change of our informationThe neuroscience will not be on the test that much The sections on LTP and LTD are really important however and we need to understand more about these two than was mentioned in the textbook So refer to slide notes and lecture notes to understand these two processes the way the professor wantsWhat is the mechanism that allows for learning and memory to take placeAnatomy of the neuron should give us more information about the way we learn and memorize In general higher organisms with a very developed central brain tend to encode information not based on just the frequency of signals It is less so in more simple systems where there are fewer neurons The opportunity to do what the mammalian brain does not exist in any other specie or computer to a degree The systems we use to learn to encode to do everything relies more so on code than frequency of signals The process of neural firingWe must first understand that a single neuron passes an all or nothing response A working neuron has a potential difference across the membrane that is maintained down the axon It uses this difference within the axon which involves the separation of charges and by changing the permeability of the membrane usually this is done in a coordinated fashion the neuron has the capacity to do work learn encode etc This is the mechanism of the propagation of signals But what is the mechanism for receiving and responding to input The axon is a tube with the inside separated from outside It has holes in it channels that can be controlled this allows ions to cross which allow changes in membrane potential which allows for changes down the axon to occur and an action potential to be firedThe separation of charge This separation really only means that different types of ions are concentrated on one side of the membrane and one on the other side of the membrane This function is mostly performed by Sodium and Potassium ions By separating charges you create diffusion potential in both directions The membrane potential is based on the fact that you have equal positive charges on the outside and inside of this membrane but on both sides you have a particular type of ion that wants to diffuse across There is a tendency or probability that potassium given the opportunity will cross form the inside to the outside and there is a probability that sodium which is concentrated on the outside will push its way in Its the electrostatic charge that holds those ions back that we measure as the potential to do work the potential difference across the membrane In the case of the neuron in general the pressure the probability that these positive charges will move out is positive because of the higher concentration and the fact that they can move more easily across the membrane more easily than the sodium ions can move back in They are carrying and providing most of that potential difference It takes more electrostatic charge to get potassium in than to keep sodium out when everything is at rest This leaves us with a tendency to be negative inside versus the outside We tend to see a negative internal cytoplasm and a positive outside This can changePropagation of a signal down a neuron changes the permeability of the membrane to one or the other of these ions The membrane separates charges the charges have to be kept in place by electrostatic charges which produce the potential to do work which is to move ions The formula on the slide represents the difference in concentrations of each ion on the inside and outside and what it takes to keep those ions where they are The voltage overall that one measures is the function of the difference inside and outside mainly potassium Understand what is going on in this equation How the membrane potential is produced How does it transmit a signal The difference between the neuron and its membrane and just a plain wire is that when you put a voltage at one end of a wire you can detect it almost instantly at another end But it takes a while for a neuron to charge up and thats because the membrane is a capacitor It doesnt allow all charges to go across It then takes a while to switch of the voltage When the voltage reaches a certain threshold something else happens in the membraneThe permeability of the membrane changes so that different ions can move through with different probabilities In the beginning of an action potential we see that it starts of with a positive feedback effect You make the inside of the cell more positive and then at some point the sodium channels open up because of that and more sodium can potentially move in This creates an even more positive charge This causes the rising charge for an action potential Very quickly after that the sodium channels are deactivated and potassium channels open up bringing the membrane potential back down There is then a refractory period It is there to allow the channels to reset so that they may be open again Why does the action potential tend to move in one direction once it is propagated It can be that an action potential goes both ways but usually once it is initiated it tends to move in one direction and not spread out As the action
More Less

Related notes for PSY260H1

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.