Unit 1 (Biological Bases of Behavior) is the foundation of AP Psychology — concepts from this unit appear in FRQs across all 5 units, not just Unit 1 prompts. Learn these terms precisely.
Neuron Structure and Function
Dendrites — branch-like extensions that receive signals from other neurons. Cell body (soma) — integrates incoming signals and keeps the cell alive. Axon — long fiber that transmits impulses away from the cell body toward other neurons or muscles. Myelin sheath — fatty insulating layer around the axon; speeds signal transmission; produced by glial cells (Schwann cells in PNS, oligodendrocytes in CNS). Axon terminals (synaptic knobs) — release neurotransmitters into the synapse. Synapse — the tiny gap between one neuron's axon terminal and another neuron's dendrite; neurotransmitters travel across it. Reuptake — the axon terminal reabsorbs unused neurotransmitters from the synapse; SSRIs block serotonin reuptake.
Action potential — the electrical signal that travels down the axon; all-or-nothing (either fires fully or doesn't fire). Threshold — the minimum level of stimulation needed to trigger an action potential. Resting potential — neuron's default electrical charge (−70 mV inside) when not firing.
Key Neurotransmitters
Acetylcholine (ACh) — muscle movement and memory; low ACh → Alzheimer's; botulinum toxin blocks ACh release. Dopamine — movement, reward, motivation; low → Parkinson's; excess → schizophrenia symptoms; cocaine/amphetamines flood dopamine system. Serotonin — mood, sleep, appetite; low → depression; SSRIs (Prozac, Zoloft) increase serotonin. Norepinephrine — alertness, arousal, fight-or-flight; also implicated in depression. GABA — main inhibitory neurotransmitter; reduces neural firing; low GABA → anxiety; alcohol and benzodiazepines enhance GABA. Glutamate — main excitatory NT; learning and memory. Endorphins — natural pain relief and pleasure; released during exercise ("runner's high") and injury; opiates mimic endorphins.
The Nervous System
CNS — Central Nervous System: brain + spinal cord. PNS — Peripheral Nervous System: all nerves outside brain and spinal cord. Somatic nervous system — voluntary muscle control. Autonomic nervous system — involuntary organs (heart, lungs, digestion). Sympathetic division — fight-or-flight: heart rate up, digestion down, pupils dilate, adrenaline released. Parasympathetic division — rest-and-digest: heart rate down, digestion resumes, pupils constrict.
Brain Regions
Brainstem — oldest brain structure; regulates survival functions (breathing, heart rate, arousal). Contains medulla (vital reflexes), pons (sleep/arousal), and reticular formation (alertness filter). Cerebellum — balance, motor coordination, and learned motor sequences. Limbic system — emotion and memory: hippocampus (new memory formation), amygdala (fear and emotion processing), hypothalamus (hunger, thirst, temperature, sex drive; controls pituitary). Cerebral cortex — higher thinking; 4 lobes: Frontal (reasoning, planning, motor strip, Broca's area for speech production), Parietal (touch, spatial awareness, sensory strip), Temporal (hearing, language comprehension — Wernicke's area, face recognition), Occipital (vision).
Research Methods
Experiment — only method that can establish causation; requires random assignment to conditions. Correlation — shows relationship (positive, negative, zero) but NOT causation. Survey — large sample, self-report bias. Case study — in-depth single subject; not generalizable. Naturalistic observation — behavior in natural setting; no cause-effect.
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