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PSY105_Chapter 3

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PSY 105
Kristin Vickers

Chapter 3: Neuroscience How Do Scientists Study the Nervous System? - Examining autopsy tissue - Testing the behaviour of patients with brain damage. - Electroencephalograms (EEG)—recording brain activity from the surface of the scalp - Animal studies - Neuroimaging techniques that show visual images in awake humans Brain Imagining: Watching the Brain in Action - Structural Neuroimaging Techniques use advanced technology to create images of the living, healthy brain o Computerized axial tomography (CT) scan o Magnetic resonance imaging (MRI) - Functional Brain Imaging Techniques allow us to watch the brain in action o Positron emission tomography (PET) o Functional magnetic resonance imaging (fMRI) How Does the Nervous System Work? Neurons - Cells in the nervous system that communicate with one another to perform information-processing tasks - About 100 billion neurons in the brain - Neurons vary in size and shape, depending on their location and function - Motor, sensory, & interneurons - Glia: Cells that help support neurons - Astrocytes: Create blood-brain barrier, influences communication between neurons, and helps heal brain damage o One type of astrocytes is the stem cell, which creates new neurons - Oligodendroglia: Provide myelin to speed up transmission of neurons - Ependymal cells: Create and secrete cerebrospinal fluid (CSF) - Microglia: Clean up dead cells and prevents infection in the brain The Structure of a Neuron  Cell Body: contains nucleus, which provides energy for the neuron (C)  Dendrites: receive messages from other neurons (B)  Axon: carries information away from the cell body (D)  Axon Terminals: transmit signals to the dendrites (E)  Myelin Sheath: A substance that speeds up the firing of the neuron (F)  Nodes of Ranvier: The small gaps on the neuron that have no myelin covering (A) How Neurons Communicate - Neurons are not in direct contact with one another - Synapse: the region of neural transmission between axon of a neuron & the dendrites or cell body of another cell Synaptic Transmission Between Neurons - Action potential reaches end of axon & neurotransmitter is released into synapse, collected at receptors of receiving neuron - Neurotransmitters: chemicals that transmit information across synapse to receiving neuron’s dendrites. - Receptors: parts of cell membrane that receive neurotransmitter & start a new electric signal. The Neuron - Dendrites o Receive information - Cell Body - Axon - Axon Terminal How Do Neurons Work? - Resting potential—When a neuron is at rest o It is negatively charged inside and positively charged outside. This resting charge is maintained through the actions of sodium-potassium pumps. o Resting potential of a neuron is – 70 millivolts - Action potential—When a neuron fires o Pores in the neuron (ion channels) open to let the positive charge come in and the negative charge go out. This shift in electrical charge triggers the axon terminals to release neurotransmitters o Action potential of a neuron is +50 millivolts (Action Potential Figure from text) Communication Between Neurons - An action potential triggers the release of neurotransmitters from within vesicles o Neurotransmitters are chemicals that help neighbouring neurons talk to each other o These chemicals float from the synaptic vessel of one neuron and are taken up by the neurotransmitter receptors in a neighboring neuron. o Synapse—the small space between neurons  Plasticity—Repeated release of neurotransmitters can cause permanent change to the neurons All or None Principle - Either a neuron is sufficiently stimulated to start an action potential (all) or it is not (does nothing) - Refractory period—After firing, a neuron can’t fire for 1000th of a second. o Absolute refractory period—a short time after an action potential, during which a neuron is completely unable to fire again o Relative refractory period—just after the absolute refractory period, during which a neuron can only fire if it receives a stimulus stronger than its usual threshold level Neurotransmitter Receptors - Postsynaptic potentials: electrical events in postsynaptic neurons occurring when a neurotransmitter binds to a receptor. The electrical response of the postsynaptic cell is determined by the receptor. - Depolarized regions of postsynaptic membranes have been become less negative, making it more likely that the neuron they initiate an action potential - Hyperpolarized areas of a cell have had their negative charge incre
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