Unit 1: Biological Bases of Behavior Redo

Nature vs. Nurture: The Big Question

The core debate about how much behavior and mental processes are due to inherited traits (nature) versus environmental influences (nurture)

Heredity (Nature)

Genetic or inherited traits that influence physical, behavioral, and mental characteristics

Environmental Factors (Nurture)

External influences—family, education, experiences—that shape behavior and mental processes

Evolutionary Psychology

The study of how evolution and natural selection have shaped human behavior to maximize survival and reproduction

Behavior Genetics

Examines the role of both genes and environment in shaping behavior, often using twin and adoption studies

Twin Studies

Comparisons of identical (100% shared genes) versus fraternal (≈50% shared genes) twins to estimate genetic influence

Identical Twins

Twins from one fertilized egg; share 100% of their genes

Fraternal Twins

Twins from two separate eggs; share about 50% of their genes

Minnesota Twin Project

Longitudinal study of identical twins reared apart; showed high similarity in IQ and personality despite different environments

Adoption Studies

Compare adoptees with their biological and adoptive families to separate genetic and environmental influences

Heritability

The proportion of trait variation in a population attributable to genetic differences

Central Nervous System (CNS)

The brain and spinal cord; processes information and directs actions

Brain

The control center for thoughts, emotions, and actions

Spinal Cord

The “information highway” that transmits messages between the brain and body

Peripheral Nervous System (PNS)

Nerves branching from the CNS to the rest of the body

Autonomic Nervous System (ANS)

Regulates involuntary bodily functions (e.g., heart rate, digestion)

Sympathetic Nervous System

Branch of the ANS that activates “fight-or-flight” responses

Parasympathetic Nervous System

Branch of the ANS that promotes rest, digestion, and homeostasis

Somatic Nervous System

Controls voluntary muscle movements and transmits sensory information

Neuron

The basic building block of the nervous system; a cell that transmits information via electrical and chemical signals

Dendrites

Branch-like extensions of a neuron that receive messages from other cells

Soma (Cell Body)

The neuron's life-support center containing the nucleus

Nucleus

Houses the cell’s genetic material and controls firing decisions

Axon

A long fiber that carries an action potential (electrical message) away from the soma

Myelin Sheath

Fatty insulation around the axon that speeds up signal transmission

Nodes of Ranvier

Gaps in the myelin sheath where the action potential jumps, further speeding conduction

Schwann Cells

Glial cells in the PNS that produce the myelin sheath

Axon Terminal

The endpoint of an axon where neurotransmitters are released

Terminal Buttons

Small knobs at the axon’s end that store and release neurotransmitters

Reuptake

The process of excess neurotransmitters being reabsorbed by the sending neuron

Glial Cells

Support cells in the nervous system that provide structure, insulation, and waste removal

Reflex Arc

A simple neural circuit in the spinal cord that produces an automatic response to a stimulus

Sensory Neurons

Afferent neurons that carry messages from sensory receptors to the CNS

Interneurons

Neurons within the CNS that communicate between sensory and motor neurons

Motor Neurons

Efferent neurons that carry instructions from the CNS to muscles or glands

Resting Potential

The neuron’s stable, negative charge (≈–70 mV) when not firing

Threshold

The minimum level of stimulation (≈–55 mV) needed to trigger an action potential

Action Potential

A brief electrical charge that travels down the axon when a neuron fires

Depolarization

Sodium (Na⁺) gates open, Na⁺ rushes in, making the inside of the neuron positive

Repolarization

Potassium (K⁺) gates open, K⁺ rushes out, restoring the negative interior charge

Refractory Period

A short period after firing during which a neuron cannot fire again

All-or-None Principle

A neuron either fires completely or not at all; no partial action potentials

Synapse

The tiny gap between the axon terminal of one neuron and the dendrites of another

Receptor Sites

Specialized spots on the receiving neuron where neurotransmitters bind

Excitatory Neurotransmitters

Cause the next neuron to be more likely to fire

Inhibitory Neurotransmitters

Cause the next neuron to be less likely to fire

Dopamine

Mood, reward, arousal; too much → schizophrenia/addiction; too little → Parkinson’s

Serotonin

Mood, appetite, sleep; too much → hallucinations; too little → depression

Norepinephrine

Alertness, arousal, mood; too much → anxiety; too little → depression

Glutamate

Main excitatory neurotransmitter; too much → migraines, seizures

GABA

Main inhibitory neurotransmitter; too little → anxiety, epilepsy, insomnia

Endorphins

Pain relief and pleasure; too little → possible addiction link

Acetylcholine (ACh)

Muscle movement, learning, memory; too little → Alzheimer’s

Substance P

Transmits pain signals in the brain and spinal cord

Agonists

Drugs that mimic or enhance a neurotransmitter’s effects

Antagonists

Drugs that block or inhibit a neurotransmitter’s effects

Endocrine System

A slow-acting communication system using hormones to regulate body processes

Pituitary Gland

The “master gland” that controls other endocrine glands; secretes growth hormone

Pineal Gland

Secretes melatonin to regulate circadian rhythms and sleep-wake cycles

Adrenal Glands

Produce adrenaline for short-term stress and cortisol for long-term stress

Leptin

Hormone from fat cells that decreases hunger and increases metabolism

Orexin

Hormone from the hypothalamus that triggers hunger

Ghrelin

Hormone from an empty stomach that signals hunger to the brain

PYY

Hormone from the digestive tract that signals fullness

Oxytocin

Hormone associated with bonding, empathy, and trust

Psychoactive Drugs

Chemicals that alter perceptions, moods, and consciousness

Tolerance

The diminishing effect of a drug with regular use, requiring larger doses

Withdrawal

Unpleasant symptoms when a drug use is reduced or stopped

Dependence (Addiction)

A compulsive craving and use of a drug despite negative consequences

Depressants

Drugs that slow down brain activity (e.g., alcohol, barbiturates, opiates)

Alcohol

Reduces inhibitions and judgment, impairs memory and reaction time

Barbiturates

Sedatives that can be addictive and dangerous in overdose

Opiates

Painkillers (e.g., morphine, heroin) that can lead to overdose

Stimulants

Drugs that increase brain activity and bodily functions (e.g., caffeine, amphetamines)

Caffeine

Boosts alertness and energy by blocking adenosine receptors

Nicotine

Highly addictive stimulant found in tobacco products

Amphetamines

Suppress appetite and increase energy; risk of anxiety and dependence

Methamphetamine

A potent, illegal stimulant with severe health risks

Cocaine

Intense euphoria by blocking dopamine reuptake; high addiction potential

Ecstasy (MDMA)

Increases empathy and euphoria; risks include dehydration and serotonin damage

Hallucinogens

Alter perceptions and cause hallucinations (e.g., LSD, THC)

LSD

Powerful hallucinogen causing unpredictable sensory effects and “trips”

Marijuana (THC)

Alters perception, impairs coordination and memory; potential lung damage

Lesions and Ablation

Intentional damage/removal of brain tissue to study function

Electroencephalogram (EEG)

Records electrical brain activity via scalp electrodes

Magnetic Resonance Imaging (MRI)

Uses magnetic fields and radio waves to produce detailed brain images

Functional MRI (fMRI)

Measures brain activity by tracking blood flow changes

Positron Emission Tomography (PET)

Uses radioactive tracers to map brain metabolism and activity

Computerized Tomography (CT)

X-ray “slices” to produce cross-sectional brain images

Deep Brain Stimulation (DBS)

Electrical impulses delivered by implanted electrodes to treat disorders

Transcranial Magnetic Stimulation (TMS)

Noninvasive magnetic pulses to stimulate or inhibit brain regions

Cerebral Cortex

The brain’s outer layer, divided into two hemispheres, for higher mental functions

Corpus Callosum

Bundle of nerve fibers connecting left and right cerebral hemispheres

Frontal Lobe

Executive functions, decision-making, motor planning, personality

Parietal Lobe

Sensory processing for touch, pressure, temperature, and pain

Occipital Lobe

Primary area for visual processing

Temporal Lobe

Auditory processing, language comprehension (Wernicke’s area), pattern recognition

Agnosia

Loss of ability to recognize familiar objects, often from temporal lobe damage

Medulla

Brainstem structure that regulates heart rate, breathing, and vital reflexes

Pons

“Bridge” in the brainstem that relays signals between brain regions