PSY12000.003 1 1 Neuroscience and Behavior Chapter 2 PSY 12000-003 Study Tips • Space your learning. – A little bit at a time, within a day, and across days. • Paraphrase – In your own words • Transmitter Mind Set (“Teaching”) rather than Receiver Mind Set (“Student”) – Pretend your are reading material in preparation for teaching someone. 2 Scientific American Video • Michael Gazzaniga and Alan Alda talk about split brain research 3 http://www.pbs.org/saf/transcripts/transcript703.htm#5 4 Overview of Chapter History Neural Communication Neurons How Neurons Communicate How Neurotransmitters Influence Us The Nervous System The Peripheral Nervous System The Central Nervous System The Endocrine System The Brain The Tools of Discovery Older Brain Structures The Cerebral Cortex Our Divided Brain Left Brain-Right Brain 5 History of Mind Plato correctly placed mind in the brain. However, his student Aristotle believed that mind was in the heart. Ancient Conceptions About Mind Today we believe that everything that is psychological is simultaneously biological. 6 History of Mind In 1800, Franz Gall suggested that bumps of the skull represented mental abilities. His theory, though incorrect, nevertheless proposed that different mental abilities were modular. Phrenology Bettman/ CorbisPSY12000.003 2 7 Neural Communication The body’s information system is built from billions of interconnected cells called neurons. Note: This is a motor neurons. Other types of neurons look different How Do The Neurons Communicate? • Until the early 20th century, scientists assumed that synaptic communication was electrical. However, through the careful histological examinations of Ramón y Cajal (1852–1934), a 20 to 40 nm gap between neurons, known today as the synaptic cleft, was discovered. This discovery cast doubt on the existence of electrical transmission. • In 1921, German pharmacologist Otto Loewi (1873–1961) confirmed that neurons communicate by releasing chemicals. Furthermore, Otto Loewi is accredited with discovering acetylcholine—the first known neurotransmitter. 8 9 Levels of Analysis We are a biopsychosocial system. Cellular Level (Interconnected Neurons) Organ Level (Brain) System Level (Information Processing) Individual Level (Human Being) Group Level (Family) Ethnic Level (Culture) Community Level (Society) 10 Neural Communication Note the similarities in the above brain regions, which are all engaged in information processing. Neurobiologists and other investigators understand that humans and animals operate similarly when processing information. 11 Neuron A nerve cell, or a neuron, consists of many different parts. ? Axons carry signals “away” Dendrites “detect” messages 12 Let’s Review: Parts of a Neuron Cell Body: Life support center of the neuron. Dendrites: Branching extensions at the cell body. Receive messages from other neurons. Axon: Long single extension of a neuron, covered with myelin [MY-uh-lin] sheath to insulate and speed up messages through neurons. Demyelinating disease leads to multiple sclerosis, Guillain-Barré Syndrome. Conduction of signals are impaired or lost. Terminal Branches of axon: Branched endings of an axon that transmit messages to other neurons.PSY12000.003 3 13 Action Potential A neural impulse. A brief electrical charge that travels down an axon and is generated by the movement of positively charged atoms in and out of channels in the axon’s membrane. 14 Depolarization & Hyperpolarization Depolarization: Depolarization occurs when positive ions enter the neuron, making it more prone to firing an action potential. Hyperpolarization occurs when negative ions enter the neuron, making it less prone to firing an action potential. 15 Threshold Threshold: Each neuron receives depolarizing and hyperpolarizing currents from many neurons. When the depolarizing current (positive ions) minus the hyperpolarizing current (negative ions) exceed minimum intensity (threshold) the neuron fires an action potential. 16 Refractory Period & Pumps Refractory Period: After a neuron fires an action potential it pauses for a short period to recharge itself to fire again. Sodium-Potassium Pumps: Sodium-potassium pumps pump positive ions out from the inside of the neuron, making them ready for another action potential. 17 Action Potential Properties All-or-None Response: When the depolarizing current exceeds the threshold, a neuron will fire. If the depolarizing current fails to exceed the threshold, a neuron will not fire. Intensity of an action potential remains the same throughout the length of the axon. 18 Synapse Synapse [SIN-aps] a junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. This tiny gap is called the synaptic gap or cleft.PSY12000.003 4 19 Neurotransmitters Neurotransmitters (chemicals) released from the sending neuron travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing it to generate an action potential. (Electrical impulse) 20 Reuptake Neurotransmitters in the synapse are reabsorbed into the sending neurons through the process of reuptake. This process applies the brakes on neurotransmitter action. 21 How Neurotransmitters Influence Us? Serotonin pathways are involved with regulating mood, sleep, food intake, and pain tolerance. Low levels of serotonin produce: insomnia, depression, food cravings, increased pain sensitivity, aggression, and poor body-temperature regulation. From Mapping the Mind, Rita Carter, © 1989 University of California Press 22 Dopamine Short term surges of dopamine are normally associated with feelings of pleasure. Abnormally HIGH concentrations of dopamine are associated with schizophrenia. Delusions (false beliefs) Hallucinations (false perceptions) Abnormally LOW levels of dopamine are associated with Parkinson’s disease hand shaking lack of facial expressions, weak voice slowness of movement shuffling steps, muscle stiffness, imbalance, intellectual decline), and attention deficit disorder. From Mapping the Mind, Rita Carter, © 1989 University of California Press 23 Neurotransmitters 24 Lock & Key Mechanism Neurotransmitters bind to the receptors of the receiving neuron in a key-lock
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