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Lecture 3

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University of Toronto St. George
Ashley Waggoner Denton

Biological foundations – Deadline for online questionaire – PSYNUp- open for experiments – Tutorial – thursday January 31st -5-6 LM159 – Q andAnswer session – Academic success centre – 3-4 14 college street Genetics – nature and nurture are intertwined – Research on twins- monozygotic twins – helpful for research because they are genetically identical- what is nature vs nurture? The nervous system – body's electrochemical communication circuitory – nerve cells – make up nervous system – 1 cm ^3 cube would contain 50 million nerve cells; brain = 80 billion nerve cells – CNS – the brain + spinal cord – peripheral nervous system- deals with every other part of the body – somatic nervous system- external environment – autonomic nervous system – internal sensation – sympathetic system – parasympathic system Neurons – are the basic unit of the nervous system – operate through electrical impulses – are excitable- communicate with other neurons through chemical signals – 3 types – Sensory neurons- info from environment to the brain- I am feeling this in my hand right now – Motor neuron- info from the brain to the external world- tell your hand to hold the water bottle – interneuron – reflect arc – SAME – sensory afferent motor efferent Neuron parts – come in all different shapes and sizes – the picture is just the general part idea – Dendrites- branch like extension from neurons- receive info from the other nearby neurons – cell body- integrates all the info that dendrites receive – axon – along which axon potential flows or propogates – mylein sheath- help info move quickly down the axon – White matter- axon – Cell body = grey matter – terminal button- contains vesicles with neurotransmitters – neurons don't touch one another- they use electrochemical signal- released into the synapse and collected by the other dendrites How is a neuron like a 14 year old girl? – one presynaptic neuron, one post-synaptic – is the person excited enough to pass the information along to other person – is she being encouraged by other people or inhibiting? Whole bunch of peopple= whole bunch of neurons? – Asingle neuron gets info from many other neurons – it has to decide what to do with the info Excitatory signals – increase the likelighood of passing on the neuron- depolarize the neuron- making it likely that they will fire Inhibitory signal- make it hyperpolarized- doesn't fire The whole reason neurons works is because they are polarized When do neurons fire? Action potential- neuron impulse that passes along the axon – causing the release of chemicals (neurotransmitters) from the terminal buttons to be picked up by other neurons All- or – none – neurons either fire or don't. What can differ the frequency of firing – it can keep firing or stop- but it doesn't kind of fire- you either pass the info or you don't Blue = outside the neuron Inside = neuron polarization – when neuron is not firing – the inside is more negatively charged than outside at its resting state – the two ions we focus on are potassium and sodium ions – these ions can only travel through their specific channels – if the gates are closed they can't travel through Resting membrane potential – stick figure diagrams – K+ = females – Na+= males – boy specfic and girl specific doors – bouncers are blocking the doors – at the resting membrane potential- the guys only let girls through – so more potassium ions inside- na+ outside – as soon as sodium channels open- the guys rush in; girls freak out and rush out second later – Things balance back out – repolarization – more negative inside than outside Neurotransmitters – stored in vesicles – during an action potential- at the end of an axon- the neurotransmitters fuse at the membrane and get let otut – synapse = space between pre and post synaptic neuron – particular neurotransmitter locks on to a specific post synaptic neuron – **What's a synaptic cleft? – 3 things can happen – If there is a lot of neurotransmitters in synapse – to stop signalling, it can lock onto autoreceptor to signal stop sending neurotransmitters – Reuptake- neurotransmitter is released back into the neuron – Enzyme deactivation- breaks down neurotransmitters so can't attach to the receptor Alot of common neurotranmitters 1. acetylcholine- responsible for motor control at muscles and joints- bottocks- small dose of bottulism- prevents acetly choline from working – it paralyzes movement- no wrinkles 2. epinephrine- adrenaline -old school term- responsible for rapid energy 3. norepinephrine- similar – responsible for alertness 4. serotonin- low levels of serotonin = depression disorder;*** SSRI what increases serotonin and decreases obsessive compulsive disorder? 5. Dopamine- rewarding behaviour 6. GABA- major inhibitory neurotransmitter; glutamate- major excitory neurotranmitter How drugs work? 2 types 1. Agonist- enhance neurotransmitters' actions - it can do this in a number of ways: - drug might increase the release of neurotransmitters (release more) -block the re-uptake of neurotransmitter - mimicking a neurotranmitter- lock onto post synaptic receptor – and by activating it- e.g. cocaine, methamphetamine- increase the effect of dopamine – by limiting it's uptake 2. Antagonists- inhibit neurotransmitters actions by: - block the release of neurotranmistters - destroy the neurrotranmitters in the synapse - mimick a neurotransmitter- but instead of activating the postsynaptic receptor, it locks onto it and blocks it by preventing the actual neurotransmitter from binding e.g. beta-blocker – prevent epinephrine from locking to the beta receptors botox- inhibits the effect of acetyl choline Brains clearing up myth 1. size of the brain has no correlation to their intelligence- elephants and whales have a larger brain than humans- if you look at the ratio of body mass to brain mass – 1:15; others' is 1:180- we have an advantage – particular parts of the brain like cortex tend to be larger 2. We only use 10% of our brains = myth came from William James – the average person rarely achieves portion of his/her potential – fernology – you can figure out a lot about person's personality depending on where the bumps on someone head were plasticity – brains are extremly adaptive The brain- from the bottom up 1. brain stem- survival 2. cerebellum- cauliflower looking important for movement 3. subcortical structures- emotions and basic drive 4. Cortical structure- complex mental activity as well as motor control The brain stem – responsible for those things that keeps you alive – super basic survival needs – e.g. digestive system control – reticular formation- network of neurons extends from brain stem and go all the way to cerebellum -responsible for allertness structure Cerebellum – cor coordinated movement and balance – belly dancing for coordinated movement and balance -bell = cerebellum What happens when alcohol reaches cerebellum? - you lose control Subcortical – Hypothalmus – master regulatory structure – hypothalmus links neurochemical system to hormone system(endocrine system) – Vital to 4 things: – fighting – fleeing – feeding – “mating” – Thalmus – Gateway to the brain – thalmus perceives all external sensory information(vision, touch, sound) except for smell – Thalmus decides which part of the brain it needs to go to – Thalmus - relay session – Conjoined twins- this specific pair share a bridge between thalamus – interesting because it take incoming sensory information and interprets in a specific way – one of them might have sensory incoming signal (e.g. might see something)- krystal will experience it e.g. might reach out and grab it – Hippocampus – important for memmory – particularly important for storage of new memories- spatial memories – Looks like a sea horse – in london, if you want to drive a black taxi cab, the drivers have to take this crazy test with a map of entire city and etc. – people who have this knowledge – are their brains different from people who don't have crazy amount of spatial memmories stored – found that their hippocampus were larger on size – neurons are probably becoming more complex and more synapses are occuring- volume of neurons for a particular structure in the brain was changed – Amygdala – memories tied to a particular emotion or music – intensify memories during emotional arousal – Morning of september 9/11 is in most of our memories – the study of what happened – new yorkers- difference based on how close they were to where the event happened – they had to recall their memories – downtown manhattan – memories included a lot of sensory info- particular sound/ sight/ smell etc – midtown manhattan- not as much sensory related memories – both has activation in hypothalmus but only amygdala activation for those who were close by – Basal gangila – key for movement – information will go from cortex (primary motor) to basal ganglia... – imagine – you have an egg shell- hold it tight enough so you don't break it but at the same time don't drop it- get info from brain to fingers – usually repetative behaviour -e.g. throwing a pitch – these type of movements basal gangila is important for Cerebral cortex – outer layer of the brain – cortex comes from the word for bark (tree bark) – Corpus callosum- massive bridge of axons that connects the left and right hemisphere – allows for communication between one another – 4 lobes – Occipital lobe -very large for vision – Temporaral lobes -especially important for hearing – Parietal lobes – touch – frontal lobes- the front part of the brain – for planning and movement – prefrontal cortex- that makes us us – gives us a personality Prefrontal cortex – huge proportion of our brain -30% – complexity of the structure probably more important than its size – executive functions e.g.planning, decision making – social behaviour – behaving properly with other people – we know a lot about it due to Phineas Gage – railroad construction worker- metal rod went through his eye and up through his brain- but he seemed okay – he woke up and was fine – he could talk and stuff even though he had a rod through his brain- obviously took out the rod – he was no longer him- personality changed- he couldn't hold down a job or behave socially – lost vision in one eye – Died earlier from ceisures- but survived long – there is a theory that he re-learned the behaviour – recovered from the injury Motor cortex – part of the frontal lobe –
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