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University of Toronto Scarborough
Ted Petit

PSYB65 Human Brain and Behaviour Lecture 4 –Neuronal functioning, epilepsy, and transmitter substances (Chapter 2, 3, 14) Monday, October 1, 2012 Introduction  Michael J. Fox o Parkinson’s disease  Affects dopamine, makes it depressed  Dopamine system doesn’t work well, can’t move or walk properly, he shakes  Underactive dopamine  Ted’s sister o Has schizophrenia (hallucinates) o She got the gene which caused her dopamine system to be overactive Basic Processes of How Neurons Work  Neurons are the cells thatcommunicate things  They communicate through a membrane which has channels in them  These channels open up for various reasons  electrically or chemically stimulated  When they open, there’s a high proportion of sodium on the outside of the cell  When these pores open up, sodium goes in  Sodium has a positive charge on it and when it moves in o There is an excitatory stimulus o The ICF becomes more positive, as it becomes more positive, it reaches a potential and causes ion channels to open up and that’s when the sodium moves in  Information comes into the dendrites and then there is an action potential  When you get a little sodium in, it reaches a threshold and opens EVEN more sodium channels and the neuron fires and that’s called: ACTION POTENTIAL: a positive electrical charge across a membrane by the influx of Na ions  The terminal button on the presynaptic sidesynaptic cleft SYNPASE!postsynaptic side  Presynaptic: has synaptic vesicles, when the action potential comes the SV fuse to the membrane and release the neurotransmitter  Synaptic clef is the middle part  Postsynaptic: has the receptors and take in the neurotransmitters Life cycle of a transmitter substance: (slide1)how to help Michael J. Fox or his sister  Awareness of the steps that a transmitter goes through 1. Synthesis o has to be made, manufactured. o Take two basic ingredients and make them combine o Mechanism in neurons o Place where you can interfere and balance out dopamine by increasing or decreasing it 2. Storage o Stored or packaged inside the synaptic vessel o can be critical, floating around in the presynaptic will be recycled and destroyed by other chemicals, they need to be packaged and ready to use 3. Release o released through a mechism when there is an action potential, but there are other times when it isn’t needed. o Released on stimulation to the synaptic clef 4. Receptor interaction o on the postsynaptic side o Interact with the receptor 5. Inactivation o The NT has to be taken away; if it’s always there then it won’t really transmit any info. Method of inactivation: two ways: i. Take it back up into the presynaptic cell, get rid of the transmitter by reabsorbing it back into the presynaptic cell to get it out of the cleft  reuptake ii. Break it down, destroy it, tear it up 6. Reuptake o Breakdown, degradation o There are always chemicals that are ready to breakdown the NT o You can only do to things to a system: increase or decrease Steps in the Transmitter cycle Increase the functional activity of the Decrease the functional activity of the system system Synthesis Increase for Michael J. Fox Decrease for his sister Packaging N/A Decrease the packaging, blocking it where chemicals will break it down (especially for his sister) Release More release, more transmitters Stop the release and slow it down stimulated Receptor activation More activated, stimulate many as Activate few, so decrease through possible through mimickers blocker Inactivation Decrease deactivation Increase its destruction Functional activity of the dopamine system  Could be increased or decreased  Look at the steps in the cycle of the transmitter and see where you need to increase or decrease dopamine levels  SYNTHESIS: for J.FOX we want to increase the functional activity of dopamine. Give him more L-dopa and that will make more dopamine. To increase the functional activity of a system: you increase the synthesis of that NT  PACKAGING: for FOX: increase the packaging, don’t want anything to be leaky. He doesn’t know if there is a drug that does do this  RELEASE: for FOX: you want to increase it, to increase the action potentials  RECEPTOR ACTIVATION: for FOX: put a mimic  MIMICKERS: look like the NT but, it’s not the NT. If you look at the NT they look similar, but aren’t. they activate the receptors the same way o Look exactly like the transmitter substance o Example cocaine  Identical to a natural transmitter in the brain o Can sit on NT and act like them o Increase activation  BLOCKERS: There are other chemicals that look like the NT, enough to sit on the receptors. It sits and fits perfectly in the receptor but doesn’t activate the receptor  INACTIVATE: for FOX: by decreasing the inactivation you double the activity of the NT  SYNTHESIS: for his sister: you want to decrease the dopamine  PACKAGING: for sister: decrease the packaging, so the dopamine will be destroyed/broken down  RELEASE: for his sister: decrease  RECEPTOR ACTIVATION: for sister: put blocker  INACTIVATE: for sister: increase the inactivators to breakdown more of the dopamine Classic transmitters: what they are, how they’re made A. MONOAMINES: (BIOGENEIC AMINES) inactivation by reuptake o Catecholamines (2 types)  DOPAMINE (DA)  NOREPINEPHRINE (NE) aka (NA)  Synthesis: TYROSINE  DOPA  DA  NE o SERATONIN: (5HT)  Synthesis: Tryptophan5OHT5HT  All of these are inactivated through reuptake B. ACETYLCHOLINE (Ach)  Synthesis: Choline +acetyl coA Ach  Inactivation: breakdown  Acetyl cholinesterase ( AChE) breaks down the Ach Treating Patients  To treat J.Fox you give him L-Dopa, which increases the synthesis of dopamine Epilepsy Pathology –General Overview  Epilepsy: it is a repetitive discharge (firing) of a hyper excitable col
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