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PSYC1000 - Module 04

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PSYC 1000
Harvey Marmurek

Course: PSYC*1000 (DE) Professor: Harvey Marmurek Schedule: Summer, 2012 Textbook: Psychology – Tenth Edition in Modules authored by David G. Myers Textbook ISBN: 9781464102615 Module 04: Neural and Hormonal Systems Why are psychologists concerned with human biology? • German physician Franz Gall proposed phrenology (studying bumps on skull); Britain had 29 phrenology societies at one time • Localization of function – the idea that various brain regions have particular functions • Biological Perspective o The body is composed of cells o Among these are nerve cells that conduct electricity and ‘talk’ to one another by sending chemical messages across a tiny gap that separates them. o Specific brain systems serve specific functions (though not the functions that Gall proposed) o We integrate information processed in these different brain systems to construct our experience of sights and sounds, meanings and memories, pain and passion. o Our adaptive brain is wired by our experience. What do phrenology and psychology’s biological perspective have in common? They share a focus on the links between biology and behaviour Phrenology faded because it had no scientific basis – skull bumps don’t reveal mental traits and abilities. What are neurons, and how do they transmit information? (See pg 48 for image) • Building blocks are neurons (or nerve cells) o Each neuron consists of a cell body and its branching fibres (dendrites) o Dendrites receive info and conduct it toward cell body o Axon fiber passes message through its terminal branches to other neurons o Drendites listen, axons speak o Dendrites short, axons long (projecting several feet through the body) o Myelin laid don up to age 25 – neural efficiency, judgment and self-control grow o Myelin sheath degenerates – MS results – communications to muscles slow and eventual loss of muscle control • Neurons generate electricity from chemical events.  Neuron’s chemistry-to-electricity process, ions (positively charged atoms) are exchanged  Fluid outside an axon’s membrane mostly positively charged ions  Resting axon’s fluid interior has mostly negatively charged ions  This positive-outside/negative-inside state is called the resting potential.  Axon’s surface is selectively permeable • Neuron fires – security parameters change  First section of axon opens its gates; positively charged sodium ions flood through cell membrane – depolarizes that section, causing another axon channel to open, and then another, etc.  Resting pause (refractory period), pumps positively charged sodium ions back outside; then it can fire again • Each neuron is itself a miniature decision-making device performing complex calculations as it receives signals from hundreds, even thousands, of other neurons. Most signals are excitatory, and some are inhibitory. If excitatory signals minus inhibitory signals exceed a minimum intensity, or threshold, the combined signals trigger an action potential. The action potential then travels down the axon, which branches into junctions with hundreds or thousands of other neurons or with the body’s muscles and glands. o Increasing the level of stimulation above the threshold will not increase the neural impulse’s intensity. The neuron’s reaction is an all-or-none response. (Squeezing the trigger of a gun harder won’t make the bullet go faster When a neuron fires an action potential, the information travels through the axon, the dendrites, and the axon’s terminal branches, but not in that order. Place these three structures in the correct order. Dendrites, axon, axon’s terminal branches. How does our nervous system allow us to experience the difference between a slap and a tap on the back? Stronger stimuli (the slap) cause more neurons to fire more frequently than happens with weaker stimuli (the tap). How do nerve cells communicate with other nerve cells? • Sir Charles Sherrington, physiologist, (1857-1952) noticed that neural impulses were taking an unexpectedly long time to travel a neural pathway – meaning there must be a brief interruption in the transmission; meeting point between neurons called a synapse • Spanish anatomist Santiago Ramon y Cajal (1852-1934) – near-unions called “protoplasmic kisses” What happens in the synaptic gap? What is reuptake? Neurons send transmitters (chemical messengers) to one another across this tiny space between one’s neuron’s terminal branch and the next neuron’s dendrite. In reuptake, a sending neuron reabsorbs the extra neurotransmitters. How do neurotransmitters influence behaviour, and how do drugs and other chemicals affect neurotransmission? • Neurotransmitters affect specific behaviours and emotions o Acetylcholine (Ach) * enables muscle action, learning, and memory  with Alzheimer’s disease, Ach-producing neurons deteriorate o Dopamine * influences movement, learning, attention, and emotion  Oversupply linked to schizophrenia. Undersupply linked to tremors and decreased mobility in Parkinson’s disease o Serotonin * affects mood, hunger, sleep, and arousal  Undersupply linked to depression. Some antidepressant drugs raise serotonin levels o Norepinephrine * helps control alertness and arousal  Undersupply can depress mood o GABA (gamma-amniobutyric acid) * A major inhibitory neurotransmitter  Undersupply linked to seizures, tremors, and insomnia o Glutamate * A major excitatory neurotransmitter; involved in memory  Oversupply can stimulate brain, producing migraines or seizures (whih is why some people avoid MSG, monosodium glutamate in food • Candace Pert and Solomon Snyder (1973) – radioactive tracer to morphine • Drugs and other chemicals alter neurotransmission o Suppressing the body’s own neurotransmitter production – nature charges a price o Agonists – bind to its receptor and mimic its effects o Antagonists – produce a temporary high by amplifying normal sensations of arousal or pleasure – bind receptors but their effect is instead to block a neurotransmitter’s functioning Serotonin, dopamine, and endorphins are all chemical messengers call Neurotransmitters What are the functions of the nervous system’s main divisions, and what are the three main types of neurons? • Peripheral Nervous System (PNS) o Somatic  Enables voluntary control of skeletal muscles o Autonomic  Controls glands and muscles of internal organs  Sympathetic Nervous System – arouses and expends energy  Parasympathetic Nervous System – conserves energy, calms • Central Nervous System (CNS)
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