AP Psychology / Unit 2: Biological Bases of Behavior

Nature

genetic predisposition, inherited, innate, hereditary

Nurture

environmental influences

Evolutionary explanations of behavior

behavior explained by the need for survival (e.g. survival of the fittest, adaptation, passing on genes)

Natural selection

principle that the inherited traits enabling an organism to survive or reproduce in a particular environment will most likely be passed down over time

Eugenics

idea that humans can be improved through selective breeding of populations to eradicate genetic defects and improve the human species (based on Darwin’s theory of evolution, Francis Galton’s research on hereditary genius)

Behavioral genetics

the study of the relative power and limits of genetic/environmental influences on behavior

Heritability

the genetic contribution (%) of a particular trait or behavior

Epigenetics

the study of how genetics are controlled by factors other than an individual’s DNA sequence

Identical (monozygotic) twins

develop from a single fertilized egg, splits in two (organisms genetically identical)

Fraternal (dizygotic) twins

develop from separate fertilized eggs (genetically no closer than ordinary siblings but shared a prenatal parent)

Adoption studies

compares adoptive child to biological/adoptive parents

Neuron

receive sensory input (sensory), process info and integrate with prior experiences (inter), output to guide our actions (motor neurons)

Soma

cell body, maintains neuron health, Na+/K+

Dendrites

receive messages from other cells (neurotransmitters)

Axon

passes messages away from the cell body to other neurons, muscles, glands

Action potential

electrical signal traveling down axon

Terminal buttons/branches

neurotransmitters flow out of the neuron, junctions with other cells

Myelin sheath

speeds up action potentials, most important axons myelinated, cover axon

Multiple Sclerosis

autoimmune disorder where immune system attacks myelin

Synapse

space between neurons (don’t touch)

Glial (glia) cells

support neurons (stimulate growth, repair damage, keep them in place)

Action Potential Step 1

Dendrites receive info from other neurons and send the info to the soma (cell body)

Action Potential Step 2

When a neuron is at its resting potential, the soma is polarized (highly negative charge): message causes soma to depolarize (positive ions come inside and causes the cell to be less negative)

Action Potential Step 3

If the cell reaches its threshold, an action potential (electrical impulse) is fired

Action Potential Step 4

Impulse moves down axon (sodium gates are opening in a chain reaction, allowing more positive ions to enter); energy/impulse pushed along axon

Action Potential Step 5

Vesicles pushed down to the axon terminals where they release neurotransmitters (chemicals) into the synapse/synaptic cleft

Action Potential Step 6

Neurotransmitters bind to receptors on dendrites of the next neuron

Reuptake (step 7)

after binding, the sending neuron reabsorbs the neurotransmitters back into the axon terminal

Refractory period (step 8)

cell going back to rest (polarized again), another action potential can’t fire

All-or-none principle

a cell is either firing an action potential or not firing

Neurotransmitters

chemical messengers released from a neuron’s terminal branches, bind to receptor sites on a neighboring neuron, bind in a lock/key fashion (specific neurotransmitters bind to specific reception sites)

Excitatory signals

more positive ions, neuron more likely to fire an action potential (depolarizing and likely to hit threshold)

Inhibitory signals

less likely to fire an action potential (remains highly polarized)

Agonist

mimics a neurotransmitter (binds to receptor to activate), prevents reuptake, or increases production/release

Antagonist

blocks receptor sites, preventing neurotransmitter from binding, or decreases production/release

Acetylcholine (ACh)

enables movement (transmitted from motor neurons to muscles), involved in learning and memory, many ACh receptors in hippocampus (e.g. pushing the brake/accel), undersupply = Alzheimer’s; deterioration of ACh brain neurons)

Dopamine

helps brain coordinate and initiate physical movement, released in response to pleasurable experiences (good, more likely to do again, reward pathway); influences motivation/goal directed behavior, influences cognition + executive function (e.g. enjoyment going past traffic), oversupply = schizophrenia, undersupply = Parkinson’s (deterioration of dopamine producing neurons)