Unit 2: Biological Bases of Behavior
AP Psychology: 67 practice questions with detailed explanations.
Unit Study Guide
Executive Summary
Unit 2 grounds behavior in biology: neurons, brain structures, endocrine signals, and the altered states produced by sleep and drugs.
Neurons and firing
Neurons receive signals at dendrites, integrate them at the soma, and fire action potentials down the axon. The resting potential is negative inside; depolarization past the threshold triggers the all-or-none spike. Neurotransmitters cross the synapse: excitatory (glutamate) or inhibitory (GABA). Reuptake, enzymes, and diffusion end the signal.
Nervous system
The CNS (brain and spinal cord) is surrounded by the peripheral nervous system: somatic (voluntary) and autonomic, which splits into sympathetic (arousal, fight-or-flight) and parasympathetic (calm, rest-and-digest).
The brain
Brainstem handles life support; cerebellum coordinates movement; the limbic system (amygdala, hippocampus, hypothalamus) drives emotion and memory; the cerebral cortex handles complex cognition. The four lobes: frontal (executive function, Broca's area), parietal (sensation), occipital (vision), temporal (hearing, Wernicke's area). Left hemisphere: language and logic; right: spatial processing — but the brain is highly interconnected.
Endocrine system
Hormones act slowly and last long: adrenaline/epinephrine and cortisol (stress), oxytocin (bonding), melatonin (sleep). The pituitary is the master gland.
Sleep and dreaming
Sleep cycles through NREM stages and REM (rapid eye movement, vivid dreams) about every 90 minutes. Sleep serves restoration and memory consolidation. Insomnia, narcolepsy, and sleep apnea are the major disorders.
Psychoactive drugs
Depressants (alcohol, barbiturates) slow the CNS; stimulants (caffeine, cocaine, amphetamines) speed it; hallucinogens (LSD) distort perception; opioids relieve pain. Tolerance and withdrawal mark physical dependence.