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– Early 1800s– Read bumps on skull

to understand traitsTouch my sexy

head lumps. Go on….touch them!

Biopsychology Today

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

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– 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!

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

– 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

PresynapticNeuron

PostsynapticNeuron

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– 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

The Nervous System (diagram)

The Autonomic Nervous System (diagram)

Fight-or-flight response

Sympathetic: Arouses Parasympathetic:

Calms

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

Central Nervous System

Brain Spinal Cord

I rule.

The Endocrine System (diagram)

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

I hate being naked in

front of all these

students…

Tell me

about it!

Endocrine Glands (diagram)

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

Got diabeeetus?

Dunno.

diabeetusfetus

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– 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

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

Cortex Breakdown…

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!

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 (1922-2009) Rat Studies (1950s-60s)

Implications for humans?

Party!

Hey guys! Check out our phat crib!

Shafted again.

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?

– Genetics? – Fetal testosterone levels?– Learned?– Handedness and sexual orientation?

A 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– 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

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,

slow-to-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

– 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

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– 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?

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– Critical Periods– Rosenzweig revisited– Brains are shaped by our genes AND

experience 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

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 DevelopmentAggression, 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!

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