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Psychology - Biological Basis of Behaviour.docx

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PSYC 2510
Richard N Lalonde

` September 26, 2012 Psychology – Lecture #4 Biological Basis of Behaviour Organization of the Nervous System Nervous System Central Nervous System Peripheral Nervous System (processes, interprets, stores (transmits information to information; issues orders to and from the CNS) muscles, glands & organs Brain Spinal Cord Somatic Nervous System Autonomic Nervous System (bridge between brain (controls skeletal (regulates glands, blood & peripheral nerves muscles) vessels, internal organs Sympathetic Parasympathetic Nervous System Nervous System The Central Nervous System (mobilizes body for (conserves energy, quiet • Brain action, energy output) state) • Spinal cord o from the base of the brain down the center of the back o protected by spinal column The Withdrawal Reflex Peripheral Nervous System • Somatic o nerves connected to sensory receptors & skeletal muscles o afferent (incoming) & efferent (outgoing) nerves • Autonomic o sympathetic system mobilizes resources & increases energy during emotion and stress (eg. you’re alone on a dark street and you hear footsteps – overdrive kicks in) o parasympathetic system operates during relaxed states & conserves energy (eg. you see that the footsteps were those of a runner who just passed you – you feel relieved) The Autonomic Nervous System Communication in the Nervous System • Neurons (nerve cells): workers ‐‐ transmit info o glial cells: bodyguards -- feed & protect Structure of a Neuron • Dendrites - receive info from other neurons and transmit to cell body. • Cell body - contains nucleus; decides “to fire or not to fire” • Axon - conducts impulses (fire signal) away from cell body Structure of a Neuron o Myelin Sheath o fatty insulation from glial cells surrounding axon o multiple sclerosis: loss of myelin causes erratic signals New view on neurons • neurogenesis: production of new neurons from immature stem cells • stem cells: immature cells that renew themselves and can develop into any cell type in the appropriate environment o harvested from embryos, fetuses, umbilical cords, placentas, & in adults How Neurons Communicate • Axon terminals release neurotransmitters • Neurotransmitter enters synaptic gap • Neurotransmitter binds to receptors that it fits • Excitatory signal (positive) Fire! • Inhibitory signal (negative) Hold your fire! Action Potential • Cell at rest (resting potential): polarized membrane (neg. molecules/ions inside & pos. outside) • Cell body averages out signals & decides if it should fire. • Cell in action (action potential ‐‐ AP): membrane depolarised & pos. sodium ions flood in • AP is an electrical signal that follows an all‐or-none law (same strength); the intensity of stimulation is determined by the rate of firing (the more intense the stimulation, the more the neuron fires) From Postsynaptic Potentials to Neural Networks • One neuron gets signals from thousands of others • Requires integration of signals – PSPs (+ & ‐) add up, balance out • Neural networks – patterns of neural activity: interconnected neurons that fire together/sequentially • Synaptic connections – elimination and creation: synaptic pruning (peak in baby months) Neurotransmitters • Specific neurotransmitters work at specific synapses – lock & key • Acetylcholine (ACh): muscle control, memory & emotion - Alzheimer’s – ACH deficit Example neurotransmitters – Monoamines • Dopamine: movement, learning, emotion Parkinson’s -- dopamine degeneration • Norepinephrene: heart rate, learning, memory, emotion, dreaming & waking • Serotonin: arousal, sleep, mood, pain suppression, & appetite Prozac – antidepressant Redux – appetite suppressant Other chemical messengers • Endorphins (endogenous opioid peptides): natural opiates – reduce
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