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Module 4.docx

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PSYC 1000
Dan Meegan

Module 4: Neural and Hormonal Systems Biology, Behaviour and Mind - Everything is a biological happening o Ideas, moods urges - Plato o Placed the mind in the head  Aristotle  Placed it in the heart - Gall o Phrenology, study bumps on the head  Reveal persons mental abilities and character traits  Would give skull readings o Failed but focused attention on localization of function  Various brain regions have particular functions - Biological perspective o Concerned with the links between biology and behaviour o Biology of the mind has lead to  The body is composed of cells  Among them nerve cells conduct electricity and “talk” to one another by sending chemical messages across tiny gap separating them  Specific brain systems serve specific function (different from Galls)  And they have subsystems  We integrate information processed in these different brain systems to construct our experiences of sights and sounds, meanings and memories, pain and passion  Our adaptive brain is wired by our experience o Cells organize to form body organs, which form larger bodily systems o Thus biopsychosocial systems Neural Communication - Brain samples of humans and monkeys are same - Able to study neural systems of squids and slugs o All operate similarly Neurons - A nerve cell, a basic building block of the nervous system o Each consists of cell body and branching fibers  Dendrite fibers are bushy branching extensions receiving messages and conduct impulses toward the cell body o Dendrites listen, axons speak o Axons very long several feet  Encased in myelin sheath  Fatty tissue, insulates and speeds impulses  Myelin laid up to age 25, neural efficiency, judgment and self control grow - Transmit messages when stimulated by signals from senses or by chemical signals from neighbouring neurons o Response is firing an impulse  Action potential, brief electrical charge travels down axon  Travels 2-180 miles an hour  3 mil times slower than actual electricity  Brain is more complex than a computer but much slower at simple responses  Slower the bigger the animal - Neurons generate electricity from chemical events (chemistry-to-electricity process) o Ions (electrically charged atoms) are exchanged  Axon outside membrane fluid is positive  Axons interior is negative  This is known as resting potential - Surface picky about what comes through, selectively permeable o Security changes when a neuron fires  First section on axon opens, positive sodium ions come in  Depolarizes axon section causing next to open and so on.. - During resting period (refractory period) o Positive ions are pumped back outside o After this can fire again - In myelin neurons speeds up because hopes from one end to the next - Types of signals o Excitatory  Pushes a neurons accelerator o Inhibitory  Pushes the brake o Is excitatory minus inhibitory exceed threshold  Level of stimulation required to trigger a neural impulse  Combined signal trigger action potential - Then travels down axon, and branches into junctions - Increasing level of stimulation does not increase neural impulse’s intensity o All or nothing response o Strong stimulus trigger more neurons to fire  Doesn’t affect potential strength or speed How Neuron’s Communicate - Once thought neurons were fused to each other - Sherrington o Neural impulses take longer than they should  Brief interruption in transmission o Synapse  Meeting point between neurons  Less than millionth of an inch wide - Cajal o Protoplasmic kisses - When action potential reaches axon end releases chemical messengers o Neurotransmitter molecules cross synaptic gap, bind to receptor sites on receiving neuron, electric charged ions flow in - Reuptake o Neurotransmitters reabsorption by the sending neuron How Neurotransmitters Influence Us - Neurotransmitters interact, effects vary with receptors they stimulate - Acetylcholine o Learning and memory o Messenger between every junction of:  Motor neurons  Carry info from spinal cord to tissue  And skeletal muscles o When Ach released muscle cell receptors, muscle contracts  When blocked we cannot move (under anesthesia) - Pert+Solomon o Attached radioactive tracer to morphine  Showed where it was taken in the brain  Bound to receptors linked with mood and pain - Brain produces own natural opiates o Released on response to pain and exercise, endorphins Nerotransmittters and Their Functions Neurotransmitter Function Examples of Malfunctions Acetylcholine Enables muscle action, learning With alzheimer
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