Lecture Four –PSYB65H3
There are no cures for these, but medication is getting better and better.
Parkinson’s disease is a disease that effects dopamine (under-active); you can’t move, get out of
o Dopamine is a transmitter substance in the brain
o Since there is not enough, you have to zap that system up
o How do you do that?
Schizophrenia: dopamine is overactive
o We need to calm down the dopamine
How neurons work:
o Neurons are the cells that communicate information; they do this through the
membrane (like all cells) and the membrane has channels in it.
o These channels open up for various reasons. You can electrically or chemically stimulate
them to open up.
o When they are open, there is a high proportion of sodium on the outside of the cell.
Whenever the pores open up, the sodium gets to come in.
o Sodium has a positive charge on it, so whenever it comes inside the cell it makes the
inside of the cell more positive
o When a neuron is sitting at rest on the baseline, it has a negative charge on the inside,
when you stimulate it for some reason, the charge goes up and it becomes more
positive. There is a threshold, if it reaches the threshold, it starts to trigger and it fires.
o Whenever it hits threshold, all of a sudden, all of the channels in that area open up and
the sodium comes in and drives the internal portion of the cell up. Whenever it
happens, the cell is said to have fired.
o The fire ignites the next and heats until it reaches the end of the axon which is the nerve
terminal. The information flows from the end of one axon to the dendrite of the next.
The contact point between the nerve terminal on the axon and the dendrite is called the
synapse. This information has to cross the synapse.
o Presynaptic(relating to the transmitting end of a discharge across a synapse) to
postsynaptic (situated after a synapse.). The gap in the middle is called the synaptic
o In the presynaptic side (presynaptic membrane) the nerve terminal, there are little guys
in there known as synaptic vesicles (like little m&ms) they are little packages like
balloons filled up with water that live in the synapse. They have a chemical inside that
transmits information so we call them transmitter substances.
o Each synaptic vesicle has transmitter substances (chemicals that are squirted out to
transmit information) What happens when you get an action potential?
The synaptic vesicles with the transmitter substance moves over to the presynaptic
membrane, they release the transmitter substance into the synaptic cleft. The
postsynaptic membrane has little receptacles (receptors) for the transmitter
substance. The transmitter substance crosses over the synaptic cleft, interacts with
the receptor site and causes a series of changes that go on the receptor on the
membrane. Whenever it interacts it opens up the channels and allows sodium to
come in on the postsynaptic neuron. It stimulates the postsynaptic side (just like the
presynaptic side was stimulated) sodium came in, made it positive fired, sodium
pours into the next cell, if its strong enough it will fire, if not it will come back to
How can we alter these transmitter substances to help someone out?
Lifecycle of transmitter substance:
1. Synthesized: it has to be made. Where transmitters are synthesized. This is the first place you
can interfere to see if you can either increase transmitters or block it
2. Stored: stored in synaptic vesicle. Once it is made and stored
3. Whenever an action potential comes along, the synaptic vesicle merges with the presynaptic
membrane and the transmitter substance is released upon activation into the synaptic cleft.
4. It has to interact with the receptor.
5. Inactivation: you can do this in two ways, you have to get rid of it:
a. you can take it back up into the presynaptic cell “reabsorbing” out of the cleft
b. break it down/tear it up/ destroy it Parkinson’s disease
We need to find a drug that increases the activity “the functional activity” of the
o Synthesis: increase synthesis
o Packaging/storage: increase –method unknown
o Release: increase release (release more)
o Receptor activation: increase activation (there are chemicals called
mimickers that look like the transmitter substance itself) it is not the
transmitter but it looks just like it. For example, cocaine is a mimicker. They
can go in and sit on the receptors as if the real transmitter’s substance
would have done. That’s how you increase receptor activation.
o Inactivation: decrease inactivation so that you will stop it from breaking
We need to find a drug that decreases the activity “the functional activity” of the
o Synthesis: decrease synthesis
o Packaging/ storage: decrease: drugs that make the vesicles leaky (doesn’t
work well) slow it down.
o Release: decrease release (slow it down)
o Receptor activation: decrease activation-if you want to decrease the
functional activity: you can use a blocker (a chemical) that blocks the