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Chapter 3 Biopsychology and the Foundations of Neuroscience Copyright © Allyn & Bacon 2007 What is Biopsychology? Biopsychology: The specialty in psychology that studies the interaction of biology, behavior, and mental processes Neuroscience: Interdisciplinary field that focuses on the brain and its role in psychological processes How Are Genes and Behavior Linked? Evolution has fundamentally shaped psychological processes because it favors genetic variations that produce adaptive behavior. How Are Genes and Behavior Linked? Innate: Inborn; present at birth; part of the organism’s biological heritage Evolution: The gradual process of biological change that occurs in a species as it adapts to its environment Evolution and Natural Selection Natural selection: The driving force behind evolution, by which the environment “selects” the fittest organisms How Natural Selection Works Environmental pressure (changes in the environment) Competition (for resources) Selection of fittest phenotype (from among a variety of phenotypes) Reproductive success (genotype corresponding to fittest phenotypes passed to next generation) Frequency of that genotype increases (in next generation) Genes and Inheritance Genotype: An organism’s genetic makeup Phenotype: An organism’s observable physical characteristics Mutations: Genetic variations, which occur randomly, especially during the recombination of chromosomes in sexual reproduction Chromosomes, Genes, and DNA DNA: A long, complex molecule that encodes genetic characteristics Genes: The functional units of a chromosome Composed of nucleotides Chromosomes: Tightly coiled threadlike structures along which the genes are organized Sex chromosomes: The X and Y chromosomes that determine our physical sex characteristics Genes influence our psychological characteristics as well as our physical traits How Does the Body Communicate Internally? The body’s two communication systems, the nervous system and the endocrine system, both use chemical messengers to communicate with targets throughout the body The Neuron Types of Neurons (specialized cell that responds to and sends signals) • Sensory neurons: carry messages from sense receptors towards the CNS (afferent – approach CNS) • Motor neurons: carry messages from CNS toward muscles and glands (efferent – exit CNS) • Interneurons: carry messages between nerve cells The Structure of a Neuron The Neural Impulse Resting potential: Electrical charge of a neuron when it is ready to fire; it’s inactive state (-70mv) (+) potassium inside; (+) sodium outside; sodium wants in! Action potential: Nerve impulse caused by a reversal in the electrical charge across the axon (- to +) Depolarization: sodium gates open; let sodium (+) in Repolarization: sodium gates close, potassium gates open and let potassium (+) out; potassium gates close when charge is leveled (back to -) Refractory period: time period in which the neuron cannot reach its action potential; repolarizing to return to its resting potential (polarized) The Neural Impulse All-or-none principle: Action potential occurs full blown or not at all; must cross threshold (minimum level of stimulation needed) Impulses only move in one direction!!! Synapse: Gap that serves as a communication link between neurons b/w terminal buttons of one neuron and dendrites of another neuron Synaptic transmission: relaying of info across the synapse by means of neurotransmitters Plasticity and Glial Cells Plasticity: Ability of the nervous system to adapt or change as the result of experience Sometimes helps the nervous system adapt to physical damage Neurons make new connections Example - sprout new dendrites Glial cells Provide structural support for neurons Help in forming new synapses Form myelin sheath Cleans up dead cells Neurotransmitters Neurotransmitters: Chemical messengers that relay neural messages across the synapse Diffuse across synapse & connect like lock and key Agonist: drug/chemical that enhances or mimics the effects of NTs – facilitates messages; turns up volume Antagonist: drug/chemical that inhibits the effects of NTs – blocks receptor sites; turns down volume Reuptake: recycling of NT back into the presynaptic neuron Turns message volume down SSRI – inhibits reuptake, so turns up volume of serotonin Reuptake in the Synapse Neurotransmitters Dopamine Normal Function: Norepinephrine Produces sensations of pleasure and reward; used by CNS neurons in voluntary movement Acetylcholine Problems with Imbalance: GABA Schizophrenia, Parkinson’s disease Glutamine Substances that Affect: Endorphins Cocaine, amphetamines, Ritalin, alcohol Serotonin Neurotransmitters Dopamine Serotonin Norepinephrine Acetylcholine GABA Glutamine Endorphins Normal Function: Regulates sleep and dreaming, mood, pain, aggression, appetite and sexual behavior Problems with Imbalance: Depression, certain anxiety disorders, obsessivecompulsive disorder Substances that Affect: Prozac, hallucinogenics (e.g. LSD) Neurotransmitters Dopamine Serotonin Norepinephrine Normal Function: Controls heart rate, sleep, sexual responsiveness, stress, vigilance and appetite Acetylcholine Problems with Imbalance: GABA High blood pressure, depression Glutamine Substances that Affect: Endorphins Tricyclic antidepressants, beta blockers Neurotransmitters Normal Function: Dopamine Serotonin Norepinephrine Primary transmitter used by neurons carrying messages from CNS; involved in some kinds of learning and memory Acetylcholine Problems with Imbalance: GABA Certain muscular disorders, Alzheimer’s disease Glutamine Substances that Affect: Endorphins Nicotine, botulism toxin, curare, atropine Neurotransmitters Dopamine Normal Function: Serotonin Most prevalent inhibitory neurotransmitter in neurons of CNS Norepinephrine Problems with Imbalance: Acetylcholine Anxiety, epilepsy GABA Substances that Affect: Glutamine Barbiturates, tranquilizers (e.g. Valium, Librium), alcohol Endorphins Neurotransmitters Dopamine Serotonin Norepinephrine Acetylcholine Normal Function: Primary excitatory neurotransmitter in CNS; involved in learning and memory Problems with Imbalance: GABA Brain damage after stroke Glutamine Substances that Affect: Endorphins PCP (“angel dust”) Neurotransmitters Dopamine Serotonin Norepinephrine Acetylcholine Normal Function: Pleasurable sensations and control of pain Problems with Imbalance: GABA Lowered levels resulting from opiate addiction Glutamine Substances that Affect: Endorphins Opiates: opium, heroin, morphine, methadone The Organization of the Nervous System Nervous system Peripheral nervous system Autonomic nervous system Sympathetic nervous system Central nervous system (CNS) Somatic nervous system Parasympathetic nervous system The Endocrine System The body’s chemical messenger system The Endocrine System Pituitary gland : Master gland Produces hormones influencing the secretions of all other endocrine glands Produces hormone that influences growth Attached to hypothalamus How Does the Brain Produce Behavior and Mental Processes? The brain is composed of many specialized modules that work together to create mind and behavior. Windows on the Brain Brain waves: Patterns of electrical activity generated by the brain EEG (electroencephalograph): Records brain waves; electrodes placed on scalp Windows on the Brain Brain scans: Recordings of the brain’s electrical or biochemical activity at specific sites CAT/CT (computerized tomography) – soft tissue, structure, x-ray PET (positron emission tomography) – activity, not structure, detects glucose in active circuits fMRI (magnetic resonance imaging) – moving pic. of brain in action The Four Lobes of the Cerebral Cortex Frontal lobes (AKA pre-frontal cortex): planning, deciding, thinking, motor cortex, personality? Parietal lobes: touch sensation, spatial relationships, somatosensory cortex Occipital lobes: contain visual cortex Temporal lobes: sounds, including speech, auditory cortex Three Layers of the Brain Brain stem structures, cerebellum, and thalamus Limbic system Drive vital functions, such as heart rate, breathing, digestion Adds emotions, complex motives, increased memory abilities Cerebrum Enables reasoning, planning, creating, problem solving Cerebrum : The Cerebrum Topmost layer of the brain; the bulbous cap over the limbic system Cerebral cortex : Thin gray-matter covering of the cerebrum; carries on thinking and perceiving (higher-order processes) Cerebral hemispheres : The two walnut shaped halves of the cerebrum, connected by the corpus callosum Important Areas Thalamus Pons Cerebellum Medulla Brain stem Reticular Formation The Limbic System Hypothalamus – Serves as the brain’s bloodtesting laboratory, constantly monitors blood to determine the condition of the body The Limbic System Amygdala – Involved in memory and emotion, particularly fear and aggression The Limbic System Hippocampus – Involved in establishing long-term memories Aphasia The impairment of language (speech or understanding) Broca’s Area – interferes w/ speech production (frontal lobe damage) can understand language words not properly formed speech is slow and slurred some aware of deficits Wernicke’s Area – loss of ability to understand language (parietal/temporal) can speak clearly most of the time words put together make no sense; word salads not aware of deficits The Cooperative Brain Association cortex: Cortical regions that combine information from various other parts of the brain Cerebral dominance: Tendency of each brain hemisphere to exert control over different functions Specialization of the Cerebral Hemispheres Left Hemisphere Right Hemisphere • Spontaneous speaking and writing • Responses to complex commands • Word rec./ speech • Memory for words and numbers • Sequences of movements • Feelings of anxiety • Positive emotion • Repetitive but not spontaneous speaking • Responses to simple commands • Facial recognition • Memory for shapes and music • Spatial interpretation • Emotional responsiveness • Negative emotion The Split Brain Split-brain patients: Individuals who have had the corpus callosum surgically severed Duality of consciousness: Condition in which a splitbrain patient has a separate consciousness in each hemisphere