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Chapter 3

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Ryerson University
PSY 105
Kristin Vickers

Neuroscience Brain Imaging: Watching the Brain in Action▯ • Structural neuroimaging techniques use advanced technology to create images of the living, healthy brain▯ computerized axial tomography (CT or CAT) scan▯ magnetic resonance imaging (MRI)▯ • Convoluted (curves) increase area which info can be stored▯ • Functional brain imaging techniques allow us to watch the brain in action. (Activity level)▯ positron emission tomography (PET)▯ functional magnetic resonance imaging (fMRI)▯ ▯ Structural Imaging Techniques▯ • Pictures in two types ▯ • Older tech is CT or cat, less expensive low resolution▯ • Newer tech MRI, higher resolution more expensive harder to get▯ ▯ Functional Imaging Techniques▯ • Older tech pET, not as preferred by of radiation, harmless but still avoided, not good for changes (red is major activity)▯ • FMRI preferred no radiation and can pick up quick changes▯ ▯ How Does the Nervous System Work? Neurons▯ • Neurons: cells in the nervous system that communicate with one another to perform information-processing tasks▯ • About 100 billion neurons in the brain▯ ▯ How Does the Nervous System Work? Glia▯ • Glia—Cells that help support neurons▯ • Examples of types:▯ • Oligodendroglia—Provide myelin (insulation material to speed things up) to speed up transmission of neurons▯ • Microglia—Clean up dead cells and prevents infection in the brain (cleaners)▯ ▯ Different Kinds of Neurons▯ • Neurons vary in size and shape, depending on their location and function▯ • Motor (moving), sensory (senses info), & interneurons (connectors)▯ ▯ The Structure of Neurons▯ • 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, only one in a neuron (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, information can jump making it move faster (A)▯ ▯ Damage to Myelin▯ • In multiple sclerosis, myelin sheath deteriorates▯ • Myelin is decaying, how to stop and why is it happening▯ Neuroscience ▯ How Neurons Communicate▯ • Neurons don't touch, space is called synapse▯ • 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.▯ • Sender neuron, presynaptic neuron▯ ▯ How Do Neurons Work?▯ • Resting potential—When a neuron is at rest▯ • It is negatively charged inside and positively charged outside. This resting charge is maintained through the actions of sodium-potassium pumps. (-70mv)▯ • Action potential—When a neuron fires▯ • 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. (+50mv)▯ ▯ The Action Potential▯ -70 mv plus sodium ion =-69▯ Enters through pores, will open up to certain chemicals (Na,K)▯ ▯ ▯ All-or-None Principle▯ • Either a neuron is sufficiently stimulated to start an action potential (all) or it is not (nothing).▯ • Refractory period—After firing, a neuron can’t fire for 1000th of a second.▯ • Absolute refractory period—a short time after an action potential (rising phase), during which a neuron is completely unable to fire again▯ • Relative refractory period—just after the absolute refractory period (undershoot), 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 become less negative, making it more likely that the neuron will initiate an action potential. (Like a power up, raises volt)▯ • Hyperpolarized areas
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