Chapter 3 Psychology 101 Notes (Comprehensive)

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Professor Stephen Killianski

- Neurons o Individual cells in the nervous system that receive, integrate, and transmit information o Permit communication within the nervous system/ external => internal stimuli o Parts of the neuron  Soma  Cell body  Contains the cell’s nucleus and much of the chemical machinery  Dendrites  Parts of the neuron that are specialized to receive information  Dendritic tree o Full set of dendrites that handle information exchange (accepting information)  Axon  Long, thin fiber that functions in the transmission of signals away from the soma -> other neurons or muscles or glands  Wrapped in cells covered with fatty substance known as myelin o Myelin sheath insulates the axons and speeds up the signal transmission (signal jumping) o Loss of muscle control due to myelin sheath degeneration = multiple sclerosis  Ends in cluster of terminal buttons o Small knobs which function in the secretion of neurotransmitters  The point at which neurons interconnect  Synapses o Junction where information is transmitted from one neuron to another  Pathway of information  Dendrites -> soma -> axon -> dendrites -> etc. - Glia o Cells found throughout the nervous system => provide neuron support o 50% brain volume o Supply nourishment to neurons, remove waste products, axon insulation o Can also send and receive signals to other glial cells o Play a role in memory formation  Deterioration could lead to Alzheimer’s - Neural impulse o At rest possesses a resting potential (-70 millivolts)  Its stable, negative charge when the cell is inactive  K and Na and Cl flowing together in equilibrium  The difference in the flow rate of ions => higher concentration of neg. charged ions inside the cell o Action potential  Brief shift in neuron’s electrical charge that travels along an axon  Stimulation of neuron => cell membrane open briefly allowing positively charged sodium ions to rush in => positively charged o After action potential fired, channels close up  Absolute refractory period = minimum length of time needed after action potential is fired during which another action potential cannot begin o Repolarization - All-or-nothing law o Once it starts it will not stop o Still can vary the strength at which the stimulus occurs by varying the rate at which the action potentials are fired - Various neurons with different variable s transmit impulses at different speeds o Thicker axons => impulses go more rapidly than thinner ones - Synaptic Transmission o Synapse = point where the axon and dendrite interconnect o Steps  Neurotransmitters, held in vesicles, are released from the axon when the neuron is stimulated  An action potential stimulates the neurotransmitter release across the synapse  The neurotransmitter binds itself to the receptor sites on the dendrites of the next neuron => change in potential => action potential, etc. o Postsynaptic potential  Voltage change at a receptor site on a postsynaptic membrane  Excitatory PSP is a positive voltage shift (increases likelihood that PSP will fire action potential  Inhibitory PSP = neg. voltage shift that decreases likelihood o Most neurotransmitters are reabsorbed through reuptake  Sponged up from synaptic cleft by presynaptic membrane - Integration of signals o If enough PSP excitatory occur in neuron => currents add up and voltage reaches threshold for action potential firing - elimination of old synapses appears to play a larger role in the sculpting of neural networks than the creation of new synapses - This elimination of old or less-active synapses is called synaptic pruning - Neurotransmitters o Acetylcholine  Activated motor neurons controlling skeletal muscles  Reg. of attention, arousal, and memory  Some reception stim. By nicotine  Agonist
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