Presentation on theme: "The Biological Bases of Behavior (Chapters 2 and 4)"— Presentation transcript:
The Biological Bases of Behavior (Chapters 2 and 4)
Plato: the mind is located in the brain Franz Gall and Phrenology Early 1800s Read bumps on skull to understand traits
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
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.
Intra neural transmission: within on neuron This is an ELECTRICAL process Occurs as a result of the exchange of charged particles called ions
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
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
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.
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!
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 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
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
Neurotransmitters regulate many aspects of behavior An imbalance of neurotransmitters may cause maladaptive behavior Neurotransmitters may be inhibitory, excitatory or both
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)
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
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
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!
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
Afferent and Efferent neurons carry messages to and from central nervous system to glands/muscles
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.
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?
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
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.
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
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
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
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
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
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!
We only use 10% of our brains? Undifferentiated cortex Association areas
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!
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.
Recent evidence has suggested that human brains may be able to generate new brain cells, known as Neurogenesis Stem cell research?
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
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
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
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?
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?
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
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
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!
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
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
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
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!
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?
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?
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?
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
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
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)
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?
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
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
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?
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