Full Psyc Unit 1

Nature–nurture

The debate over whether traits are inborn (nature) or shaped by experience (nurture).

Behavior genetics

Study of how genes and environment influence behavior.

Mutation

Random DNA replication error introducing genetic variation.

Heredity

Genetic transfer of traits from parents to offspring.

Genome

Complete genetic instructions for making an organism.

Identical twins

One egg splits into two; genetically identical.

Fraternal twins

Two eggs; genetically like normal siblings.

Interaction

When gene effects depend on environment.

Epigenetics

Study of environmental effects on gene expression.

Epigenetic marks

Chemical tags (e.g., methyl) that turn genes on/off.

Heritability

Proportion of variation explained by genes in a group.

Gene–environment

Example: genetic anxiety appears only under stress.

Nervous system

Electrochemical communication network of the body.

CNS

Brain and spinal cord; decision center.

PNS

Sensory and motor neurons connecting CNS to body.

Sensory neurons

Carry incoming info to CNS.

Motor neurons

Send outgoing instructions from CNS.

Interneurons

Communicate within CNS between sensory and motor.

Somatic NS

Controls voluntary skeletal muscles.

Autonomic NS

Controls glands and internal organs automatically.

Sympathetic NS

Arouses body for “fight or flight.”

Parasympathetic NS

Calms body after stress (“rest and digest”).

Homeostasis

Body’s tendency to maintain internal balance.

Neuron

Basic nerve cell; dendrites, soma, axon.

Myelin sheath

Fatty layer speeding neural impulses; damage = MS.

Glial cells

Support, nourish, and protect neurons.

Action potential

Electrical impulse traveling down axon.

Resting potential

Negative charge when neuron inactive (~–70 mV).

Threshold

Stimulation level required to trigger firing.

Depolarization

Na⁺ ions enter; inside becomes positive.

Repolarization

Positive ions exit; charge returns negative.

Excitatory signal

Increases chance neuron will fire.

Inhibitory signal

Decreases chance neuron will fire.

Refractory period

Time after firing when neuron cannot fire again.

All-or-none

Neuron fires completely or not at all.

Synapse

Gap between neurons where signals cross.

Reuptake

Reabsorption of neurotransmitters by sending neuron.

Axon terminal

Releases neurotransmitters into synaptic gap.

Neurotransmitters

Chemical messengers crossing synapses.

Acetylcholine

Muscle action, learning, memory; low = Alzheimer’s.

Myasthenia gravis

Immune attack on ACh sites → muscle weakness.

Dopamine

Motion, learning, emotion; high = schizophrenia, low = Parkinson’s.

Serotonin

Mood, hunger, sleep; low = depression.

Norepinephrine

Arousal, alertness; imbalance → anxiety/depression.

GABA

Main inhibitory transmitter; low = seizures/insomnia.

Glutamate

Main excitatory transmitter; excess = migraines/seizures.

Endorphins

Natural painkillers; opiates suppress production.

Substance P

Transmits pain signals; more = higher pain.

Adenosine

Promotes sleep; caffeine blocks its receptors.

Oxytocin

Bonding and trust hormone; released during affection.

Vasopressin

Regulates water and social bonding/aggression.

Histamine

Arousal and immune response; antihistamines cause drowsiness.

Melatonin

Pineal hormone controlling sleep–wake cycle.

Agonist

Mimics or enhances neurotransmitter effect.

Antagonist

Blocks neurotransmitter action at receptor sites.

Neuromodulator

Chemical altering neurotransmitter release/sensitivity.

LTP

Long-term strengthening of synapses; basis of learning.

Endocrine system

Chemical communication via hormones in blood.

Hormones

Chemical messengers affecting distant organs.

Pituitary gland

“Master gland”; releases growth hormone, controls others.

Hypothalamus

Links nervous and endocrine systems; regulates drives.

Thyroid

Controls metabolism.

Parathyroid

Regulates calcium levels.

Adrenal glands

Release epinephrine/norepinephrine for stress.

Pancreas

Controls blood sugar with insulin and glucagon.

Gonads

Produce sex hormones (testosterone, estrogen).

Pineal gland

Secretes melatonin for sleep.

HPA axis

Stress-response loop (hypothalamus–pituitary–adrenal).

Feedback loop

Hypothalamus → pituitary → glands → hormones → brain.

Psychoactive drugs

Chemicals altering perception, mood, behavior.

Tolerance

Needing larger dose for same effect.

Withdrawal

Discomfort after stopping drug use.

Depressants

Slow neural activity (alcohol, barbiturates, opiates).

Stimulants

Excite neural activity (caffeine, nicotine, cocaine, meth).

Hallucinogens

Alter perception (LSD, THC, psilocybin).

Alcohol

Enhances GABA/dopamine; impairs memory, control.

Barbiturates

Reduce anxiety but impair coordination; overdose risk.

Opiates

Mimic endorphins; relieve pain, cause euphoria.

Amphetamines

Increase dopamine; high energy, then crash.

Cocaine

Blocks dopamine/serotonin reuptake; brief euphoria.

Caffeine

Blocks adenosine; increases alertness.

Nicotine

Stimulates dopamine/norepinephrine; addictive.

LSD

Mimics serotonin; vivid hallucinations.

THC

Activates cannabinoid receptors; slows reactions.

Reward pathway

Dopamine circuit (VTA → nucleus accumbens → cortex).

EEG

Measures brain waves (electrical activity).

MEG

Measures magnetic fields from neural firing.

CT scan

X-ray images showing brain structure.

PET scan

Measures glucose use → activity.

MRI

Shows detailed brain structure.

fMRI

Shows blood flow → structure + function.

Structure vs function

CT/MRI = structure; EEG/MEG/PET/fMRI = function.

Hindbrain

Breathing, heartbeat, balance (medulla, pons, cerebellum).

Midbrain

Relays sensory info; coordinates movement.

Forebrain

Higher thought and emotion (limbic system, cortex).

Brainstem

Oldest part; automatic survival functions.

Medulla

Controls heartbeat and breathing.

Pons

Coordinates movement and sleep.

Reticular formation

Arousal and alertness; damage = coma.

Thalamus

Sensory relay (except smell) to cortex.