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Psychology 1000
Biggs- Universityof Western Ontario

Chapter 3: Biological Psychology a) The Neural Bases of Behaviour Neurons:  The basic building blocks of the nervous system are linked together in circuits and composed of: 1. A cell body (soma) - contains necessary chemical structures to keep the neuron alive. The nucleus carries the genetic information. 2. Dendrites- branchlike fibers emerging from the cell body, which, like antennas, collect messages from neighbouring neurons and send them to the cell body. Incoming information is combined and processed. 3. Axon- conducts electrical impulses away from the cell body to other neurons, muscles or glands. They branch out to dendrites and transfer information.  Glial cells surround neurons and hold them in place, manufacture nutrients, form the myelin sheath around axons and absorb toxins.  Blood- brain barrier- prevents substances (i.e. toxins) from entering the brain Nerve Conduction:  Neurons generate electricity and release chemicals  Neurons are electronegative- polarized Action Potential:  Depolarization- a sudden reversal in the neuron’s membrane voltage, during which the membrane voltage momentarily moves from -70 millivolts to +40  Potentials- when dendrites are stimulated by axons, a shift occurs  Need enough stimulation to reach the action potential threshold  Neuron discharges with an action potential  All-or-none law- either occurs with maximum intensity or doesn’t occur at all.  Graded potentials add ion channels (protein structures) to change the membrane potential  Ion channels allow ions to cross the membrane or enter/leave the cell  If the threshold is reached, a neuron will fire  Refractory period- when the membrane is not excitable and cannot discharge an action potential The Myelin Sheath:  A fatty, whitish insulation layer derived from glial cells during development  Interrupted by the nodes of Ranvier  Create high conduction speeds  Cause for timing of nerve impulses Synaptic Transmission:  Synapse- a functional (but not physical) connection between a neuron and it’s target  Synaptic cleft- a tiny group or space between the axon terminal of one neuron and the dendrite of the next neuron 1. Neurotransmitters  Chemical substances that carry messages across the synapse to either other neurons or inhibit their firing a) Synthesis- chemical molecules formed in neuron b) Storage- molecules stored in synaptic vessels within axon terminals c) Release- when AP comes down the axon, molecules release into fluid space d) Binding- cross synaptic space and bind to receptor sites e) Deactivation 2. Excitation, Inhibition and Deactivation  Binding produces a chemical reaction, which can: a) Depolarize (excite) the postsynaptic membrane by stimulating the flow of sodium ions - called excitatory transmitters, which can exceed APT b) Chemical reaction can hyperpolarize the membrane by stimulating ion channels, allowing sodium ions to flow out and Cl to flow in - becomes more negative, harder to reach APT - called inhibitory transmitters  Deactivation occurs by: - By other chemicals - By reuptake- transmitter molecules are reabsorbed into the axon terminal Specialized Transmitter Systems:  Simple amino acids, glutamate (glutamic acid) and gamma-amino-butyric acid (GABA) a) Glutamate- excitatory, learning and memory b) GABA- inhibitory, motor control and anxiety control c) Acetylcholine (Ach)- memory and muscle activity, excitatory d) dopamine- can treat schizophrenia e) serotonin- mood, eating, sleep and sexual behaviour f) endorphins- increased well-being, lessened pain b) The Nervous System 1. Sensory Neurons- carry input messages from sense organs to the spinal cord and brain (afferent). 2. Motor Neurons- transmit output impulses from the brain and spine to muscles and organs (efferent). 3. Interneurons- connective/associative functions, linking input and output  Central nervous system- neurons in the brain and spinal cord  Peripheral nervous system- neurons that connect central with muscles, glands and sensory receptors The Peripheral Nervous System:  All neutral structures outside of the brain and spinal cord a) The Somatic Nervous System - sensory neurons- transmit messages from eyes, ears, etc. and the motor neurons that send messages from the brain and spinal cord to the muscles that control our voluntary movements - groups of sensory organs= sensory nerves - groups of motor neuron axons= motor nerves b) The Autonomic Nervous System - controls the glands and the smooth (involuntary) muscles that form the heart, blood vessels and lining of the stomach/intestines - respiration, circulation, digestion, motivation, emotional behaviour and stress responses i) sympathetic- activation/arousal function, “fight or flight”, a unit, heart rate rises ii) parasympathetic- slows down body processes, heart rate lowers The Central Nervous System - Spinal cord and the brain a) The Spinal Cord  Nerves enter/leave central nervous system via spine  Neurons protected by vertebrae (bones of the spine)  Spinal reflexes- simple stimulus/response sequences, triggered without brain, speeding up reaction time b) The Brain  Most complex structure in the universe  Never rests  Methods of study: 1. Neuropsychological Tests - Used in clinical evaluations of people with brain damage - Brain-behaviour relations 2. Destruction/Stimulation Techniques - Brain damage (lesions) under controlled conditions where nervous tissue is destroyed with electricity, cold, heat or chemicals - Surgically remove a part and study consequences - Stimulating neurons by mild electric current/chemicals to excite - Electrodes implanted for repeated stimulation 3. Electrical Recording - Neuron activity measured by inserting small electrodes into areas of the brain or neurons - Placing large electrodes on scalp to measure activity of large groups of neurons with an electroenophalogram (EEG) - Abnormal sleep patterns- brain disorders, sensory stimulus 4. Brain Imaging - CT scans, PET scans, MRI (magnetic resonance imaging) - Computerized axial tomography (CT)- X-ray technology to study brain structures - Positron emission tomography (PET)- measure brain activity, including metabolism, blood flow, neurotransmitter activity  Glucose is injected into the bloodstream and travels to the brain  Energy is measured by PET- brain area lights up on the screen - MRI- creates images based on how atoms in living tissue
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