Unit 1 Psychology AP 2026 (copy)

1.1 Interactions of Heredity & Environment

• Biological Psychology – study of how biology (genes, brain, neurotransmitters) influences behavior.

• Evolutionary Psychology – studies how natural selection shaped behavior (e.g., phobias, mating preferences).

• Twin Studies – identical twins (share 100% DNA) vs. fraternal twins (share ~50% DNA) help separate nature vs. nurture influences.

• Epigenetics – environment can turn genes “on” or “off” without changing DNA (ex: trauma, diet, stress).

1.2 Overview of the Nervous System

• Central Nervous System (CNS) – brain & spinal cord (processing).

• Peripheral Nervous System (PNS) – nerves outside CNS (communication).

  • Somatic NS – voluntary control (skeletal muscles).

  • Autonomic NS – automatic functions (organs, glands).

    • Sympathetic – “fight or flight” (increases heart rate, pupils dilate).

    • Parasympathetic – “rest & digest” (slows heart, conserves energy).

1.3A Neural Communication & Endocrine System

• Neuron Parts – dendrites (receive), soma/cell body, axon (sends), myelin sheath (speeds impulses), terminal buttons (release neurotransmitters).

• Types of Neurons – sensory (afferent), motor (efferent), interneurons (connect within CNS).

• Glial cells – support, nourish, protect neurons.

Neural Firing Process

• Resting potential – neuron is at rest, negative inside.

• Action potential – brief electrical impulse → travels down axon.

• Refractory period – neuron recharges, can’t fire.

• All-or-nothing principle – fires completely or not at all.

Neurotransmitters

• Dopamine (movement, reward) – too much = schizophrenia; too little = Parkinson’s.

• Serotonin (mood, sleep, appetite) – low = depression.

• Acetylcholine (ACh) – muscle action, memory; deficit = Alzheimer’s.

• GABA – inhibitory, calming; low = seizures, insomnia.

• Glutamate – excitatory, memory; too much = migraines/seizures.

• Endorphins – natural painkillers, pleasure.

Agonist vs. Antagonist

• Agonist – mimics neurotransmitter (ex: morphine → endorphins).

• Antagonist – blocks neurotransmitter (ex: botox → blocks ACh).

Endocrine System

• Glands that release hormones into bloodstream.

• Pituitary gland – “master gland,” controls other glands, releases growth hormone.

• Adrenal glands – release adrenaline (fight or flight).

1.3B Substance Use Disorders & Psychoactive Drugs

• Psychoactive Drugs – alter perceptions, mood, behavior.

• Substance Use Disorder – craving + use despite negative consequences.

• Tolerance – need more for same effect.

• Withdrawal – discomfort when stopping.

• Addiction – compulsive drug seeking.

Categories of Drugs

• Depressants (slow CNS): alcohol, barbiturates, opiates → relaxation, slowed processing, dependence.

• Stimulants (speed CNS): caffeine, nicotine, cocaine, meth → alertness, energy, crashes.

• Hallucinogens: LSD, marijuana, ecstasy → distort perceptions, hallucinations.

1.4A The Brain: Neuroplasticity & Tools

• Neuroplasticity – brain’s ability to adapt/reorganize (esp. after damage).

• Brain Lesions – destroyed tissue used to study function.

• Brain Imaging Tools:

  • CT/MRI – structure (pictures).

  • EEG/MEG – brain waves, electrical activity.

  • PET – activity via glucose use.

  • fMRI – both structure + function (blood flow).

1.4B Brain Regions

• Hindbrain (brainstem):

  • Medulla – heartbeat, breathing.

  • Pons – movement, sleep.

  • Reticular Formation – arousal/alertness.

• Cerebellum – balance, coordination.

• Limbic System:

  • Hippocampus – memory.

  • Hypothalamus – hunger, thirst, body temp, reward.

  • Thalamus – sensory relay station.

  • Amygdala – emotion (fear, aggression).

  • Pituitary gland – hormones.

• Cerebral Cortex:

  • Occipital – vision.

  • Parietal – touch, spatial.

  • Temporal – hearing.

  • Frontal – thinking, planning, movement.

• Broca’s area – speech production.

• Wernicke’s area – speech comprehension.

• Corpus callosum – connects hemispheres.

• Lateralization – left = language, right = creativity/spatial.

• Association areas – higher mental functions.

1.5 Sleep & Consciousness

• Consciousness – awareness of self & environment.

• Dual processing – conscious + unconscious tracks.

• Circadian rhythm – 24-hour biological clock.

• Sleep Stages:

  • NREM-1: light sleep, hypnagogic sensations.

  • NREM-2: sleep spindles.

  • NREM-3: deep sleep, delta waves.

  • REM: dreams, brain active, body paralyzed.

• Melatonin – hormone controlling sleep.

Theories of Sleep – protects, helps recuperation, restores memories, growth.
Sleep Loss – weakens immune system, memory issues, obesity risk.
Sleep Disorders: insomnia, narcolepsy, sleep apnea, sleepwalking, REM behavior disorder.

Dream Theories:

• Freud’s wish-fulfillment.

• Information-processing.

• Activation-synthesis (brain makes sense of random activity).

• Cognitive development (dreams reflect brain maturation).

1.6 Sensation & Perception

Key Concepts:

• Sensation – sensory input.

• Perception – brain’s interpretation.

• Bottom-up – raw data → brain.

• Top-down – expectations influence perception.

• Transduction – sensory → neural signals.

• Absolute threshold – minimum stimulus detected 50% of the time.

• Signal detection theory – detecting depends on experience, alertness.

• Difference threshold (JND) – smallest difference detectable.

• Weber’s Law – constant % difference needed.

• Sensory adaptation – less sensitivity after constant exposure.

Vision:

• Structures: cornea, iris, pupil, lens, retina (rods = B/W, cones = color), fovea, optic nerve, occipital lobe.

• Feature detectors – respond to shapes, edges, movements.

• Parallel processing – multiple aspects at once.

• Theories:

  • Trichromatic (3 cones: red, green, blue).

  • Opponent process (afterimages, red-green, blue-yellow).

• Vision problems: myopia (near), hyperopia/presbyopia (far).

Hearing:

• Outer ear: pinna, canal.

• Middle ear: hammer, anvil, stirrup.

• Inner ear: cochlea, basilar membrane, semicircular canals.

• Place theory – pitch = location on cochlea.

• Frequency theory – pitch = frequency of impulses.

• Hearing loss: conduction (mechanical), sensorineural (cochlea/nerve damage).

Other senses:

• Touch – pressure, warmth, cold, pain.

• Gate-control theory – spinal cord “gate” blocks or allows pain.

• Smell (olfaction) – linked to memory (bypasses thalamus).

• Taste (gustation) – sweet, sour, salty, bitter, umami.

• Vestibular sense – balance (semicircular canals).

• Kinesthetic sense – body position, movement.

Unit 0: Research Methods (Quick Review)

• Longitudinal Study – same group studied over time.

• Cross-sectional Study – compare different groups at one time.