The Biological Bases of Behavior

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Peripheral nervous system Central Peripheral (brain and spinal cord) ‘Autonomic (controls Somatic self-regulated action _(controts voluntary of internal organs movements of and glands) skeletal muscles) ‘Sympathetic Parasympathetic (arousing) (calming) 

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AP Psychology Unit 2: The Biological Bases of Behavior (Chapters 2 and 4) An Early History of Biopsychology  Plato: the mind is located in the brain  Franz Gall and Phrenology – – Touch my sexy head lumps. Go on….touch them! Early 1800s Read bumps on skull to understand traits Biopsychology Today  Everything and brain – – – – – we do is ultimately controlled by our body Body/brain composed of cells Brain cells called neurons communicate electrically and chemically Different parts of the brain have specific functions Our brains create meaningful experiences from sensory information Brain structure and function is influenced by experience Neurons: Defining and Types   A NEURON is a nerve cell. There are three basic types of neurons (diagram): – – – –  Sensory Neurons: Afferent neurons that detect stimuli from sense organs and relay this information TO the brain and/or spinal cord. Motor Neurons: Efferent neurons that receive signals from the brain and/or spinal cord and relay this information to glands and muscles. Interneurons: neurons in the brain and spinal cord that coodinate activity between sensory and motor neurons. Three Types of Neurons in action! Glial Cells: provide nutrients to neurons, insulate neurons, and remove debris when neurons die. Neuroanatomy (diagram) The Neural Impulse (diagram)    Intraneural transmission: within on neuron This is an ELECTRICAL process Occurs as a result of the exchange of charged particles called ions Neural Impulse: Resting Potential      When more negative ions are inside the neuron than outside Neuron is not transmitting information Similar to a compressed spring The neuron is POLARIZED – meaning it has a charge (-) System WANTS to reach equilibrium and balance charges, but selectively permeable membrane is closed when in this state known as resting potential Neural Impulse: Action Potential      Sudden, massive change in charge in the neuron Neuron reaches the threshold of excitation when neighboring neurons’ excitatory signals outnumber inhibitory signals Ions flow across cell membrane down axon (domino effect) facilitated by myelin sheath Na+ in, K+ out Neuron fires and DEPOLARIZES – no charge Neural Impulse: All-or-None Law    A neuron either fires or it does not When it does fire, it will always produce an impulse of the same strength Intensity of a stimulus is coded by the frequency of action potentials or the number of neurons that fire Neural Impulse: Refractory  Absolute refractory period –  Relative refractory period –  Period immediately after an action potential when another action potential cannot occur Period following absolute refractory period when a neuron will only respond to a stronger than normal impulse During the refractory period, the neuron is trying to get back to resting potential by pumping out K+ ions! Dude…I’m in refractory. No action potential here… Hmpf . So…?  Impulse has traveled down the length of the axon  Signal end up at terminal buttons, very end points of the axon terminals  Then what?  Signal must get to other neurons, but how? The Synapse (diagram)  The – synapse Composed of the terminal button of one neuron, the synaptic space, and the dendrites or cell body of the receiving neuron  Synaptic – – space (synaptic cleft) Tiny gap between neurons Messages must travel across the space to get from one neuron to the next Transmission Between Neurons    Interneural: between neurons a CHEMICAL process Synaptic vesicles –  Chemicals released by synaptic vesicles Receptor sites – –  Sacs in terminal button that release chemicals into synaptic space Neurotransmitters –  Presynaptic Neuron Location on receptor neuron for specific neurotransmitter Lock and key Reuptake – “Recycling” neurotransmitters Postsynaptic Neuron Putting it together… Neurotransmitters and Behavior (diagram)    Neurotransmitters regulate many aspects of behavior An imbalance of neurotransmitters may cause maladaptive behavior Neurotransmitters may be inhibitory, excitatory or both Drugs and Neurotransmitters   Drugs’ impact on the body has helped scientists discover neurotransmitters, neuropeptides (e.g. amino acids such as endorphins) and neuromodulators that can increase or decrease the activity of certain neurotransmitters How do drugs work? – – Agonists mimic or prevent reuptake (1, 3) Antagonists block neurotransmission (2) Psychopharmacology  Botulism – –  Blocks release of ACh at the neuromuscular junction, causing paralysis “Botox” is botulism toxin used to prevent facial muscles from making wrinkles Curare – found in vines in S. America; used as poison – – Can stun or kill prey quickly Blocks ACh receptors causing paralysis  Antipsychotic medications – –  Caffeine –  Block dopamine receptors Reduces schizophrenic hallucinations Increases the release of excitatory neurotransmitters by blocking the inhibitory neurotransmitter adenosine Cocaine – – Prevents reuptake of dopamine Leads to heightened arousal of entire nervous system The Nervous System (diagram) The Autonomic Nervous System (diagram)    Fight-or-flight response Sympathetic: Arouses Parasympathetic: Calms Central Nervous System Brain Spinal Cord Central Nervous System (CNS)  Brain – – – –  Enables all functioning Billions of neurons and their connections These neurons work together in neural networks to facilitate efficient output. As we learn, these networks strengthen Spinal Cord – – Connects brain to PNS Handles reflexes I rule. The Endocrine System (diagram) I hate being naked in front of all these students… Tell me about it!     Helps coordinate and integrate complex psychological reactions Endocrine glands secrete hormones into the bloodstream Hormones serve to organize the nervous system and body Hormones also activate behavior, such as sexual behavior, hunger and aggression Dunno. Got diabeeetus? diabeetusfetus Endocrine Glands (diagram)  Thyroid gland – –  – –  – – – Regulates blood-sugar levels Secretes insulin Diabetes? –  Referred to as the “master gland” regulates many other glands Adrenal glands – Sleep-wake cycle Secretes melatonin Pancreas Pituitary gland – Pineal gland –  Secretes hormones (primarily thyroxin) that control metabolism Hypothyroidism and Hyperthyroidism  Reaction to stress Secretes adrenaline (epinephrine) Gonads – – Ovaries and testes secrete estrogens and androgens The Brain  Without our brains, we would really be nothing!  “The mind is what the brain does” Studying the Brain  Studying the brain through lesions or damaged areas – –  “Ta” and Phineas Gage Experiments in rats – hypothalamus lesions Monitoring Electrical Activity: the EEG – – – Electroencephalograms provide information about cortical activity Record electrical activity of neurons on surface of brain (neural firing) A functional technique Studying the Brain: Structural Neuroimaging Techniques  CT Scan (Computerized tomography) – –  Computer-assisted x-ray of brain Used to create overall images of brain MRI (Magnetic Resonance Imaging) – – Produces detailed pictures of soft tissue in brain Can focus on specific regions when CT cannot produce clear images CT scan (top) and MRI (bottom) showing a tumor. Studying the Brain: Functional Neuroimaging Techniques  PET (positron emission tomography) – –  Image created by the rate at which radioactive glucose is metabolized Which areas of the brain are active during a particular activity fMRI (functional MRI) – – – Combines structural and functional techniques Multiple images of brain created during a particular task Records changes in blood flow to indicate regions of greater activity Primitive Brain Structures  Brainstem – – – –  Thalamus – –  Oldest part of brain Contains medulla, controlling heartbeat, blood pressure and breathing Also contains pons, which helps regulate sensory information and facial expressions Contains Reticular Formation (RF) for alertness/arousal, sleep/wakefulness Pair of egg-shaped structures on top of brainstem Routes all incoming sensory information except for smell to appropriate areas of brain Cerebellum – – “little brain” at read of brainstem Controls coordination, balance, and muscle tone These parts of the brain are our “autopilot” so other regions can deal with higher-level “human” functions The Limbic System  Located in between the primitive parts of the brain and the cerebral hemispheres – – – Hippocampus processes new memories (case of H.M.) Amygdala controls emotions such as aggression and fear – in animals, the “attack” response (rat study) Hypothalamus regulates hunger, thirst, body temperature and sex drive – also controls pituitary gland Rat study – self-stimulation of “pleasure centers”  Human implications? Mild pleasure, addiction tendencies?   Primarily, the limbic system processes drives, smell and various emotional responses The Cortex       Part of the cerebrum, the two large hemispheres comprising 85% of brain weight Wrinkled outer layer Why so convoluted? Higher level functions Designation of cortical space and “higher level” animals? Most highly evolved part of the human brain Cortex Breakdown…  Each hemisphere is divided into 4 lobes – – – –  Frontal lobe Temporal lobe Parietal lobe Occipital lobe The lobes are separated by deep convolutions known as fissures Homunculous! Cortex Breakdown…  Occipital Lobes Parietal Lobes Visual cortex Damage? – Temporal Lobes – – –   – – Auditory cortex Auditory hallucinations?  Primary sensory or somatosensory cortex Allocation of space? Frontal Lobes – – – Most evolved Motor cortex, which allows us to move Allocation of space? Motor and Sensory Cortex Revealed! The Cortex: Association Areas  We only use 10% of our brains?  Undifferentiated cortex  Association areas Phineas Gage: A Case Study in Frontal Lobe Association Area Damage  In 1848, railroad foreman Phineas Gage – accident!  No longer “himself”  Emotions, the frontal cortex, and the unchecked limbic system The skull of Phineas and rogue tamping iron, displayed proudly at Harvard University’s medical school! For real! Neuroplasticity    Brain’s to change and reorganize as a result of experience Mark Rosenzweig’s (19222009) Rat Studies (1950s-60s) Implications for humans? Shafted again. Hey guys! Check out our phat crib! Party! Neuroplasticity in Rats Neurogenesis?  Recent evidence has suggested that human brains may be able to generate new brain cells, known as Neurogenesis  Stem cell research? The Two Hemispheres  Two halves are NOT identical  Most have a dominant hemisphere – usually the left, which controls the right side of the body  Both sides serve important functions, revealed by studying split-brain patients Split-Brain  Epilepsy, seizures and the corpus callosum  Reduction in epileptic seizures  Different abilities in each hemisphere  The story of “Vicki”  Michael Gazzaniga Some Hemispheric Strengths  Left Hemisphere – – –  Language in most people: The cases of Ta of Charles Landry Logic Right side of body Right Hemisphere – – – Perception Sense of self Inferences Hemispheric Dominance: Handedness  90% of humans are right-handed  The 10% of left-handers show less predictable patterns of hemispheric dominance  Causes? – – – – A Genetics? Fetal testosterone levels? Learned? Handedness and sexual orientation? closer look: a curse or an advantage? Behavior Genetics: What’s the Point?  Behavior Genetics seeks to understand the relative influence of our heredity and our experiences  Nature vs. Nurture? It’s both – but how much of each? Behavior Genetics: Genetics Review   Heredity examines the transmission of trait from one generation to next Chromosomes – – –  Deoxyribonucleic acid (DNA) – –  Organic molecule arranged in a double-helix Contains the “code of life” Genes – –  Pairs of thread like bodies that contain genes Average human cell has 23 pairs Sex cells? Basic units of inheritance Segment of DNA Genome – – “map” for an organism’s genetic complete make-up Human Genome Project Behavioral Genetics: Studying Nature vs. Nurture  Animal – – Studies Strain Studies Selection Studies  Human – – – – – Studies Identical Twins Fraternal Twins Separated Twins Adoption Studies Family studies Behavioral Genetics: Temperament and Heritability  Temperament refers to emotional reactivity and seems to be set very early in life – – Thomas and Chess (easy, difficult, slowto-warm-up) Kagan’s “shy child”  Indicates this aspect of behavior is genetically manipulated  Environment can enhance or diminish this genetic predisposition Behavior Genetics: Heritability  Heritability: the extent to which differences among organisms are caused by genes  Does NOT refer to which percentage of a trait is determined by genetics in a given individual!  The more similar and controlled the environment of the organisms is, the more we can attribute differences to genes, and the higher the heritability! So…Nature vs. Nurture…?  Genes and environment interact like “two hands clapping…” – – – Environment can trigger genetic “switches” Our genes can provoke us to seek particular environments e.g. Eating Disorders Genetic predisposition (some are more susceptible than others)  Cultural regulation (Western culture)   Molecular Genetics – – – Studies how particular genes influence behavior e.g. Is there a gene that determines obesity? Sexual orientation? Promise and peril of molecular genetics? Genetic engineering  Eugenics  Evolutionary Psychology   Whereas behavior geneticists seek to explain our behavioral differences in terms of our genes, evolutionary psychologists focus on our similarities, as dictated by natural selection. Richard Dawkins The Selfish Gene (1976) – – – – Varied organisms in a population compete to survive Certain biological and behavioral variations facilitate survival Surviving organisms may reproduce and pass on their genes This leads to overall changing characteristics in a population Evolutionary Psychology: Natural Selection, Adaptation and Evolutionary Success  Selection – providing a reproductive advantage, either naturally or artificially (e.g. tame foxes), based on a trait/set of traits – –  Variation can result from mutations (errors in genetic replication right after conception) – –  These traits will endure over time Population will change as a result Some of these “errors” provide an advantage and are selected for, and therefore persist The errors are adaptive – increasing our fitness, or our chances to survive (and to reproduce) Humans have so many shared characteristics – How? – – Differences that were not “fit” were not passed on Those that increased survival were, as these organisms lived and reproduced Evolutionary Psychology    Selection happens SLOWLY and often our world changes faster than the gene pool can (e.g. fatty/sweet food cravings) Today, evolutionary psychologists examine persistent trends in human behavior and seek to explain them Keep in mind, however, that genetically driven tendencies only partially govern human behavior! Evolutionary Psychology: Explaining Human Sexuality and Mating    Males of all sexualities generally are more interested in sex, regard sex as a recreational activity and prefer young, attractive mates Females of all sexualities generally see sex as an outgrowth of relationships and prefer mature, stable, and affluent mates Have these trends genetically motivated? Evolutionary Psychology: Human Sexuality and Mating  Women – – – –  Men – – Perhaps males should invest more in childrearing? Quality over quantity More invested in bearing/nurturing children Seek men who either provide superb genes (heman strategy) or are good providers (domesticbliss strategy) “fast” vs. “coy” females – – – – Quantity over quality Increase reproductive success by spreading their genes as widely as possible Attraction to fertile females Not physically bound to pregnancy He-man strategy vs. opportunists Philanderers vs. Stable males? Evolutionary Psychology: Criticism    Do these arguments just provide excuses for bad behavior? Do humans have more of a social and cultural responsibility to make the world better? What about environmental influence? – – – How does the environment reinforce these trends? How much of a role does environment play in the persistence of these roles? Who benefits? Parents and Peers  Experience and Brain Development – – –  Parental Influence? – – – –  Critical Periods Rosenzweig revisited Brains are shaped by our genes AND experience If abusive or neglectful, can have major impact In non-extreme cases, parents probably deserve less credit, or less blame! Parents shape values, beliefs and habits, but not as much as we may believe Most important to provide unconditional love and support Peer Influence – – Peers teach us how to socialize and cooperate Selection effect: seeking peers with similar interests Cultural Influences  Culture – –  distinctive values, beliefs, language and characteristics of a society both tangible (food, clothing) and intangible (values, beliefs). Norms – – Rules that represent the typical behaviors of a particular group One example is expected personal space, the distance we like to keep ourselves from other people Individualism vs. Collectivism     Individualist cultures place value of singular person over that of the group Collectivist cultures value the group over the individual Which type of culture does the US have? Why? Implications? Gender Development Aggression, Power, and Connectedness     Aggression involves an intent to harm, whether verbal or physical: males admit to and exhibit more than females. Men are and are perceived as more powerful and engage in behaviors that exhibit and perpetuate this power inequity. Females place greater emphasis on social connections, choosing careers that involve social interaction or require nurturing roles Males have more difficulty admitting they are wrong Why Are We Different? Biological Explanations     X and Y Chromosomes Y triggers sex differentiation during fetal development, causing greater testosterone production in males Female infants exposed to elevated levels of testosterone exhibit “male” behavioral characteristics Males with normal male hormones but had their sex reassigned at birth for various reasons often embrace a male identity, despite efforts to raise them as females Why Are We Different? Social Explanations  Gender Roles – expected behaviors for males and females – – – – Women as caregivers? Men as breadwinners? The Reality? Women now OUTNUMBER men in the workplace in the US, yet in 87% of families with children, are still the primary caregivers. Variations across culture and time…  Gender Identity – our sense of being male or female – –  Gender typing – embracing a traditional masculine/feminine role Social Learning Theory and Gender Schemas What do these roles and stereotypes provide for us? – – Sense of stability and simplification Sense of confinement Nature vs. Nurture? Call the Whole Thing Off! genes and our experiences form us  Family, friends, and culture have an influence over the genes that make us  Our – – – These structures are constantly in flux We are adaptive creatures The world changes, and we change with it