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CHAPTER 2: NEUROSCIENCE Neurons and Neurotransmitters ORIGINS OF STUDYING THE BRAIN Plato believed that the mind was located in the spherical head Aristotle believed that the mind was located in the heart Phrenology – Studying bumps on the head to reveal a person’s mental abilities and character traits, Franz Gall invented phrenology Gall was correct to conclude parts of the brain have specific functions. VIDEO: Racing and the brain. BIOLOGY AND BEHAVIOR Biology is the foundation for our behavior and mental processes Biological Psychologists – study links between biology and behavior Neuroscience – interdisciplinary field studying how biological processes relate to behavioral and mental processes. NEURAL COMMUNICATION Neuron – nerve cell, the building block of the nervous system Each neuron consists of a cell body (sometimes called the soma) and branching fibers Neurons send out electrochemical communications to the brain and the rest of the body Dendrite – receives information coming from the neuron NEURAL COMMUNICATION Axon – Passes information to other neurons, muscles and glands Axons can be very long (unlike the dendrite which is very short) Myelin Sheath – insulates the axon Helps impulses travel quickly Importance of the myelin sheath is seen in Multiple Sclerosis. Consider MS – the myelin sheath breaks down and results in slow communication to the muscles. NEURAL COMMUNICATION Axon Terminal Buttons ( aka end buttons / branches, synaptic vessicles) – the branched end of the axon that contains the neurotransmitters. Reaches right up to another neuron, muscle, organ. PARTS OF A NEURON ACTION POTENTIAL Neural impulses are called action potential Action Potential is a brief electrical charge that travels down an axon Where does an electrical charge come from? During the resting potential axon gates are closed and do not allow positively charged ions in. negatively charged ions are on the inside. Electrical activity must get past the threshold to fire. ALL OR NOTHING Neuron fires (aka Action Potential) --- + charged ion comes into axon. Negative ions rush out.(this depolarizes the axon) --- depolarizing causes the next gate to open and then the next… etc. (like dominoes) Neuron’s Action Potential An “all or nothing response” Like a gun firing or camera taking a picture… it does not go halfway Refractory Period When the positive ions are pumped outside of the axon. During the phase the neuron can’t re-fire as in needs to recharge. FIELD TRIP TIME. YEAH! FIELD TRIP When you come back from our very brief field trip answer how the flushing of a toilet is analogous to the firing of a neuron. During which part of the demonstration did the following occur? “all or nothing” principle Resting potential Threshold Action Potential (neural impulse) Refractory Period ACTION POTENTIAL NEURON COMMUNICATION Individual neurons function as independent agents within the nervous system Synapse – junction between the axon tip of the sending neuron and the dendrite of the receiving neuron (junction is called the synaptic gap) From the axon terminal buttons, neurotransmitters travel across the synapse NEURAL COMMUNICATION LIVE!Psych (The Synapse and Neurotransmitters) CRASH COURSE- The chemical brain 1st 4 mins 30 secs. NEURON COMMUNICATION (CONT.) When the action potential reaches the end of the axon, it triggers the release of neurotransmitters (chemical messengers) Neurotransmitters cross the synaptic gap and binds to the receptor sites on the receiving neuron. Neural Networks and learning a song (singing OR playing an instrument). Patterns are created and strengthened the more we use them. ACTIVITY NEURAL COMMUNICATION Excess neurotransmitters are reabsorbed by the sending neuron – this is called reuptake Many drugs today block the reuptake of neurotransmitters. Ex Zoloft, prozac, Paxil for Serotonin. AN EXAMPLE OF REUPTAKE … NEUROTRANSMITTERS Neurotransmitters – chemicals produced by neurons that travel across the synaptic gap and are then used for communication between neurons for the performance of mental and physical activities. Q ANY EXAMPLES? ACETYLCHOLINE (ACH) Enables cognitive skill - learning and memory Undersupply marks Alzheimer’s disease DOPAMINE Motor Movement Oversupply is linked to schizophrenia. Undersupply is linked to tremors and decreased mobility (ex. Parkinson’s disease) m Cell Stem cell Reading PARKINSON’S DISEASE AND DOPAMINE Michael J Fox Parkinson's Disease Michael j fox on family guy SEROTONIN Mood Control Undersupply is linked to clinical depression Selective Serotonin Reuptake Inhibitors (SSRI) are a frequently used drug for depression (ex. Prozac, Paxil, Lexapro, Zoloft) These drugs increase the activity of Serotonin by blocking the reuptake of serotonin NOR EPINEPHRINE Influences alertness and arousal Undersupply can depress mood ENDORPHINS Released in response to pain and vigorous exercise – linked to pain and pleasure. Ex.- Donovan McNabb, Jack Youngblood. “morphine within”. Runner’s high, exercisaholics Involved in addictions – Ex. Heroine DRUGS AND HOW THEY AFFECT COMMUNICATION AT THE SYNAPSE Agonist v. Antagonist Drugs Agonist – mimic neurotransmitters (Excite) Blocks reuptake of neurotransmitters Fits into the receptor site and function as neurotransmitters Antagonist – blocks neurotransmitters (Inhibit) Inhibit neurotransmitters from releasing Block receptor sites LIVE!Psych AGONIST V. ANTAGONIST EXAMPLE Ex. Dopamine Undersupply (Parkinson’s) – Agonist Drug. Overdosage and hallucinations (grandfather) Oversupply (Schizophrenia) – Antagonist. dyskenesia Drugs such as heroine and morphine can take the place of natural neurotransmission Brain stops producing natural opiates Body is in pain until the natural production of endorphins begins again. VIDEO- The chemical mind…crash course -1st 7 mins.