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The Biological Bases of Behavior (Chapters 2 and 4)

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1 The Biological Bases of Behavior (Chapters 2 and 4)

2  Plato: the mind is located in the brain  Franz Gall and Phrenology  Early 1800s  Read bumps on skull to understand traits

3  Everything we do is ultimately controlled by our body and brain  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

4  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! Three Types of Neurons  Glial Cells: provide nutrients to neurons, insulate neurons, and remove debris when neurons die.


6  Intra neural transmission: within on neuron  This is an ELECTRICAL process  Occurs as a result of the exchange of charged particles called ions

7  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

8  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

9  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  In other words, if there are several neighboring neurons firing, or one neuron firing repeatedly, the stimulus may be intense enough for the neuron to fire.

10  Absolute refractory period  Period immediately after an action potential when another action potential cannot occur  Relative refractory period  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!

11  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?

12  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

13  Inter neural: between neurons  a CHEMICAL process  Synaptic vesicles  Sacs in terminal button that release chemicals into synaptic space  Neurotransmitters  Chemicals released by synaptic vesicles  Receptor sites  Location on receptor neuron for specific neurotransmitter  Lock and key  Reuptake  “Recycling” neurotransmitters Presynaptic Neuron Postsynaptic Neuron


15  Neurotransmitters regulate many aspects of behavior  An imbalance of neurotransmitters may cause maladaptive behavior  Neurotransmitters may be inhibitory, excitatory or both

16  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)

17  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  Block dopamine receptors  Reduces schizophrenic hallucinations  Caffeine  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

18  All of our physical and emotional reactions are the product of communication between the brain and the rest of the body  Endocrine System = Glands (hormones)  Nervous System = Neurons  Our brain is the “supercomputer” and may instruct our glands to release hormones AS IT IS instructing the neurons in the central and peripheral nervous systems to fire  Example: You are being chased by a bear!  Brain -> Endocrine- Release adrenaline from adrenal gland  Brain -> CNS- communicate via epinephrine (NT) to excite SNS

19  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  Slower communication than Nervous System (but impacts last longer) I hate being naked in front of all these students… Tell me about it!

20  Thyroid gland  Secretes hormones (primarily thyroxin) that control metabolism  Hypothyroidism and Hyperthyroidism  Pineal gland  Sleep-wake cycle  Secretes melatonin  Pancreas  Regulates blood-sugar levels  Secretes insulin  Diabetes?  Pituitary gland  Referred to as the “master gland”  regulates many other glands  Adrenal glands  Reaction to stress  Secretes adrenaline (epinephrine)  Gonads  Ovaries and testes  secrete estrogens and androgens Brain  Pituitary  other glands  hormones  brain


22  Afferent and Efferent neurons carry messages to and from central nervous system to glands/muscles

23  Fight-or-flight response  Sympathetic: Arouses  Parasympathetic: Calms

24  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 Central Nervous System BrainSpinal Cord I rule.

25  Without our brains, we would really be nothing!  “The mind is what the brain does”  Brain + Body = Mind  We live somewhere “north of the neck”  What would happen if our brains were placed into another human’s body?

26  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

27  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.

28  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

29  Brainstem  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  Thalamus  Pair of egg-shaped structures on top of brainstem  Routes all incoming sensory information except for smell to appropriate areas of brain  Communicates with higher level of brain  Penn Station  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

30  Located in between the primitive parts of the brain and the cerebral hemispheres  Hippocampus processes new memories (case of H.M.) Hippocampus processes new memories  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 Primarily, the limbic system processes drives, smell and various emotional responses

31  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

32  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

33  Occipital Lobes  Visual cortex  Damage?  Temporal Lobes  Auditory cortex  Auditory hallucinations?  Parietal Lobes  Primary sensory or somatosensory cortex  Allocation of space?  Frontal Lobes  Most evolved  Motor cortex, which allows us to move  Allocation of space? Homunculous!


35  We only use 10% of our brains?  Undifferentiated cortex  Association areas

36  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!

37  Brain’s ability to change and reorganize as a result of experience  Mark Rosenzweig’s ( ) Rat Studies (1950s- 60s)  Implications for humans? Party! Hey guys! Check out our phat crib! Shafted again.

38  Recent evidence has suggested that human brains may be able to generate new brain cells, known as Neurogenesis  Stem cell research?

39  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

40  Epilepsy, seizures and the corpus callosum  Reduction in epileptic seizures  Different abilities in each hemisphere  The story of “Vicki” The story of “Vicki”  Michael Gazzaniga

41  Left Hemisphere  Language in most people: The cases of Ta of Charles Landry Language in most people  Logic  Right side of body  Right Hemisphere  Perception  Sense of self  Inferences

42  90% of humans are right-handed  The 10% of left-handers show less predictable patterns of hemispheric dominance  Causes?  Genetics?  Fetal testosterone levels?  Learned?  Handedness and sexual orientation?  A closer look: a curse or an advantage?

43  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?

44  Heredity examines the transmission of trait from one generation to next  Chromosomes  Pairs of thread like bodies that contain genes  Average human cell has 23 pairs  Sex cells?  Deoxyribonucleic acid (DNA)  Organic molecule arranged in a double- helix  Contains the “code of life”  Genes  Basic units of inheritance  Segment of DNA  Genome  “map” for an organism’s genetic complete make-up  Human Genome Project

45  Animal Studies  Strain Studies  Selection Studies  Human Studies  Identical Twins  Fraternal Twins  Separated Twins  Adoption Studies  Family studies

46  Temperament refers to emotional reactivity and seems to be set very early in life  Thomas and Chess (easy, difficult, slow-to-warm-up)  Kagan’s “shy child”  Indicates this aspect of behavior is genetically manipulated  Environment can enhance or diminish this genetic predisposition

47  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!

48  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 (Behavioral 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- successful in breeding “intelligent” rats  Eugenics- Blood tests before marriage; prescreening for genetic disorders

49  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

50  Selection – providing a reproductive advantage, either naturally or artificially (e.g. tame foxes), based on a trait/set of traits  These traits will endure over time  Population will change as a result  Variation can result from mutations (errors in genetic replication right after conception)  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

51  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!

52  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?

53  Women  Quality over quantity  More invested in bearing/nurturing children  Seek men who either provide superb genes (he-man strategy) or are good providers (domestic-bliss strategy)  “fast” vs. “coy” females  Men  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? Perhaps males should invest more in child-rearing?

54  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?

55  Experience and Brain Development  Critical Periods – “Use it or lose it”  Rosenzweig revisited  Brains are shaped by our genes AND experience- Lines and colors on a coloring page  Parental Influence?  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

56  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

57  Do you base your self-perception on the traits you possess (athleticism, looks, intelligence) or on your sense of belonging (relationship with friends/family)  Do you define success as performance in career or in terms of the relationships you form and the roles you fulfill.  The most important thing about a marriage is personal happiness. (T/F)  You see a froshie being teased by a group of girls for the shirt she’s wearing. The girls don’t think she heard, but you know she did. Do you step in or mind your own beeswax?  Popularity is based on  a) quality of friendship  b) amount of friends.  Your behavior (success included) is controlled by who you are and what you want to do. (T/F)

58  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?

59  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  Women internalize emotions and behavior; Men see the source of the problem as external

60  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   Tom boy!  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

61  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 Identity – our sense of being male or female  Gender typing – embracing a traditional masculine/feminine role  Social Learning Theory and Gender Schemas  Close contact, imitation of superiors  Learn about what it means to be male/female from culture  What do these roles and stereotypes provide for us?  Sense of stability and simplification  Sense of confinement  Fluidity of gender?

62  Our genes and our experiences form us  Family, friends, and culture have an influence over the genes that make us  These structures are constantly in flux  We are adaptive creatures  The world changes, and we change with it



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