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PSY105 - Chapter 3

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PSY 105
Helene Moore

CHAPTER 3­ NEUROSCIENCE  How do scientists study the nervous system? • Examining autopsy tissue: trying to see what brain really looks like when someone has passed on  testing the behaviour of patients with brain damage • First study of the brain was done by Phineas Gage  he was known to be ruthless and impulsive • Electroencephalographs (EEG): Recording brain activity and see how alert the person is • Scientists also study the system from animals and Neuroimaging techniques - show visuals in awake humans Brain Imaging • Structural Neuroimaging Techniques - create images of living and healthy brain o Computerized Axial Tomography (CT) Scan - lower resolution o Magnetic Resonance Imaging (MRI) • Functional Brain Imaging Techniques - let us watch brain in action o Positron Emmision Tomography (PET) o It is injected with harmless radioactive isotope o colors are used to indicate - warmer colors for increased function o Functional Magnetic Resonance Imaging (fMRI) - 3D fMRI is preferred because its quicker NEURONS • these are cells in the nervous system that communicate with one another to perform tasks • there are about 100 billion in the brain GILA • these cells support neurons • ASTROCYTES: create blood-brain barrier, influences communication between neurons and helps heal brain damage --> stem cell creates new neurons • OLIGONDENDROGLIA: provide myelin (made up of protein and fats) to speed up transmission of neurons • EPENDYMAL CELLS: create and secrete cerebrospinal fluid (CSF) • MICTROGLIA: they clean up dead cells and prevents infection in the brain NEURONS • they vary in shape and size, depending on location and function of it • 3 types of neurons : motor, sensory and interneurons • they move, sense and connect • spinal cord, thalamus, cerebellum, cortex STRUCTURE OF NEURONS • CELL BODY: contains nucleus which provides energy for the neuron - organelles (C) • DENDRITES: receive messages from another neuron (B) • AXON: carries information away from the cell body (D) • MYELIN SHEATH: fatty substance that speeds up the firing of neurons -sausage (F) • NODES OF RANVIER: small gaps on neurons that have no myelin covering - between sausage (A) HOW NEURONS COMMUNICATE • SYNAPSE: the region of neural transmission between axon and the dendrites or cell body of another • PRE-SYNAPTIC NEURON- before synapse (axon terminal) • POST-SYNAPTIC NEURON - after synapse (dendrites) SYNAPTIC TRANSMISSION BETWEEN NEURONS • ACTION POTENTIAL: it reaches the end of axon and neurotransmitter is then released into synapse, which is collected at receptors • NEUROTRANSMITTERS: chemicals that transmit information across synapse to receiving neuron's dendrites • RECEPTORS: parts of cell membrane that receive neurotransmitter and start a new electric signal HOW DO NEURONS WORK? • RESTING POTENTIAL: when a neuron is at rest --- it is negatively charged inside and positively charged outside. This action continues through the sodium-potassium pumps • ACTION POTENTIAL: when a neuron fires ---pores in the neurons open to let the charge come in and the negative charge go out. This shift triggers the axon terminal to release neurotransmitters COMMUNICATION BETWEEN NEURONS • Action potential triggers the release of neurotransmitters • neurotransmitters are chemical that help neighboring neurons communicate • these chemicals float from synaptic vessel of one neuron and are taken by receptors in a neighboring neuron • SYNAPSE- small place between neurons • PLASTICITY - repeated release of transmitters can cause permanent damage to neurons ALL OR NONE PRINCIPLE • REFRACTORY PERIOD - after firing, a neuron can't fire for 1000th of a second • ABSOLUTE REFRACTORY PERIOD: stage after an action potential, where neuron is unable to fire • RELATIVE REFRACTORY PERIOD: stage after absolute where neuron only fire if it receives stimulus stronger than its usual threshold level NEUROTANSMITTER RECEPTORS • POSTSYNAPTIC POTENTIALS: electrical events occurring when neurotransmitter binds to a receptor • DEPOLARIZED: regions of postsynaptic that has become less negative, making it more likely that the neuron they initiate an action potential • HYPERPOLARIZED: areas with increased negative charge, making it less likely that cell will generate action potential TYPES OF NEUROTRANSMITTERS • Dopamine - essential for normal movement, related in parka son's disease, feel good kind of chemical o it can also result in good feeling; cocaine - when high wares off, dopamine is deleted and the body will stop making dopamine overtime • Norepinephrine(NE)- involved when we feel threatened o someone is following you or creeping you out - increase in NE • Serotonin- it's important to have enough serotonin for normal eating behaviour • GABA: it is important in regulated anxiety; it is a constant feeling of worry - people with this can't stop worrying about anything • Acetylcholine(Ach): important in memory, learning and attention o Alzheimer's disease - their own body see to attack their own parts TYPES OF DRUGS • Agonists: these drugs increase the activity of a particular transmitter; treated for people who don't have enough of transmitters o example: patients with eating disorder - they are given serotonin agonist to increase the transmitters; attention deficit disorder - treated by agonist pharmaceuticals • Antagonists: drugs have too much of dopamine o example: schizophrenia - people have hallucinations, behaviour is hard to understand o this is caused by excess of dopamine in the certain part of the brain - antagonists of dopamine is bring down the levels of dopamine o epilepsy - seizures, have the abnormal of bursts of transmitters ; bring down the levels HOW IS THE NERVOUS SYSTEM ORGANIZED? • Central Nervous System: centre of the body, constituting brain and spinal cord • Peripheral nervous system - neurons outside of the brain and spinal cord o Somatic - these are neurons governs sensory input and muscle movement o Autonomic - involuntary aspects of nervous system; we don't have control over (example: heart, breathing)  Sympathetic: functions of the body speeds up when confronted by a threat; physical or psychological (example: nervous before exam-
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