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DO NOW • Make another name tag • What is a brain cell called? • Name the four major lobes of the brain • Name three parts of a brain cell • What do all drugs of abuse have in common? Drug and Alcohol Abuse Week 2: Introduction to the Brain Goals of today • (1) You will become familiar with the major parts of the brain and be able to describe their function. • (2) You will be able to explain how brain cells send and receive information. Why do we care about the brain? • All drugs of abuse change dopamine levels in the brain. (this will be on your test). • If we understand how dopamine levels in the brain arise in the first place, we can better understand drug abuse • More on this later.. The Brain The most heterogeneous part of our body In other words—it is the most complex. What makes up the brain? • Brain cell, or neurons. – ~100 billion • Glial (glue) cells – ~300 billion Neurons come in different shapes and sizes The brain is part of the central nervous system (CNS) • The central nervous system (PNS) consists of – The brain (400 billion cells) – Spinal cord • The peripheral nervous system (PNS) – Most physical sensations are via PNS – All other nerve cells • Think taste cells on your tongue, cells in your gut that tell you that you are full, cells that regulate your heart beat – More cells in the PNS than CNS – Will not talk much about the PNS, although, drugs of abuse can affect these cells • i.e. withdrawal symptoms, nausea, etc. CNS • The Brain – 3 major divisions • (1) Cerebellum • (2) Brain Stem • (3) Forebrain – – – – (a) Cerebral cortex (b) Limbic System (c) Basal Ganglia (d) Diencephelon Cerebellum • Integration of movement and stability • Very sensitive to alcohol – Think field sobriety test • Fun fact: 90% of your brain cells are in the cerebellum • Funner fact: you can live without a cerebellum and be pretty OK for the most part. Brain Stem • Medulla • Pons • Midbrain • Together important for heart rate, breathing, and reflexes Brain Stem • Regions of the brain stem are organized in nuclei – Clusters of similar neurons – Dopamine, serotonin, and norepinephrine nuclei Brain Nuclei You Need To Know • Substantia Nigra/ Ventral Tegmental Area – Dopamine (DA) • ***rewarding properties of food, drugs, sex, etc • *** all theories of addiction imply this brain region • Raphe nuclei – Serotonin (5-HT) • Locus Coeruleus – Norepinephrene (NE) Diencephelon • Thalamus – Relay center from the sensory • All sensory and motor input here – Olfaction doesn’t get processed here • Hypothalamus – Hunger, satiety, motivation for food – Contains pituitary gland (growth, hormones) Basal Ganglia • Globus Pallidus • SN/VTA Targets – Striatum • (motor) • Caudate • Putamen – Nucleus accumbens • (motivation/reward) • Shell • Core Limbic system • Amygdala – Emotion/mood – Fear • Hippocampus – Memory and learning Cerebral Cortex • Two hemispheres • Four lobes – Different functions for each lobe Four Lobes Border of Frontal and Parietal Lobe Motor cortex Somatosensory cortex Summary I • That was a lot of information! • How can you remember all of that? – – – – Make a list of all the structures we covered today Then, write down what each structure does. Repeat about 3 times Then, you will be good for the test. • What is the MOST important take home? – All drugs of abuse elevate dopamine in the nucleus accumbens. (We will give you proof!). – Without dopamine elevation in the nucleus accumbens, addiction to drugs of abuse cannot occur. What makes up the brain? • Brain cell, or neurons. – ~100 billion • Glial (glue) cells – ~300 billion Neurons come in different shapes and sizes 3 parts (1) Cell body: where all major cell functions happen (has the nucleus and organelles) (2) Dendrites: part of the neuron that “receives” information. Can listen to many cells at once. (3) Axon: part of the neuron that “sends” information • Usually wrapped in myelin (sends signal faster) • Branches out into several “axon terminals” • Can talk to many cells at once Neurons For simplicity • We will not talk about electrical properties of neurons too much – What is important is that a cell is “excited” or “inhibited”. – Excited: causes the neighbor neuron to release neurotransmitter to another neuron • When excited, neurons produce “action potentials” • Action potential: electricity, that begins in the dendrite, travels down the cell body, and down the axon. – Inhibited: prevent the neighbor neuron from releasing neurotransmitter to another neuron • When inhibited, no action potentials are fired. Communication between cells: axon terminals form “synapses” with dendrites of other cells PRESYNAPTIC NEURON POSTSYNAPTIC NEURON Signal sending and Signal receiving occurs at the synapse • Neurons “talk” by – Releasing neurotransmitters into the synapse PRESYNAPTIC NEURON POSTSYNAPTIC NEURON Signal sending and Signal receiving occurs at the synapse • Neurons “listen” by – Sensing neurotransmitters into the synapse via proteins called “receptors”. PRESYNAPTIC NEURON POSTSYNAPTIC NEURON Synapse • It is a space between the axon terminal and dendrite. – Axon terminal releases neurotransmitter into the synapse (space) – Dendrite picks up the neurotransmitter. Neuron Activity Another example A B We say the flow of information is going from cell A to D C D Another example A B C In this case, cell B is a GABA neuron, and release GABA. This shuts down cell C, which can no longer fire an action potential. D Recap • (1) Neurons release neurotransmitters from their axon terminals. • (2) The neurotransmitter can excite or inhibit the neighbor neuron – Excite: causes the neighbor neuron to release neurotransmitter to another neuron – Inhibit: prevent the neighbor neuron from releasing neurotransmitter to another neuron • (3) All communication in the brain works this way. • (4) when billions of these cells work together, communicate together, you get – – – – Thought Feelings Pleasure Pain, etc Preview of next week The synapse Types of neurotransmitters • Excitatory – Glutamate – Acetylcholine • Inhibitory – GABA – Acetylcholine • Modulatory (can excite, inhibit, and other things, dependng on the context) – Dopamine, serotonin, norepinephrine How do neurotransmitters excite/inhibit? • Key (ligand, neurotransmitter) and Lock (receptor) https://www.youtube.com/watch?v=p5zFgT4a ofA More on this later • Next week: • Neurotransmitters and how they act in the brain. • Due next week: Addiction Science in the News. Discussion