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Unit 1 Essentials

26 must-know vocabulary terms and the 6 big ideas anchoring Unit 1: Biological Bases of Behavior.

Unit 1: Biological Bases of Behavior🏠 Unit Hub📁 Flashcards🗺 Cheat Sheet⭐ The Essentials🎙 Podcast🎨 Visual Review📝 MC Practice✍ FRQ Practice
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Heredity (nature)
Genetic or predisposed characteristics that influence physical, behavioral, and mental traits.
Heredity & Env.
Environment (nurture)
External factors — family, education, culture — that shape behavior alongside heredity.
Heredity & Env.
Evolutionary perspective
Explains behavior through natural selection — traits increasing survival/reproduction were passed on.
Heredity & Env.
Twin/adoption studies
Research designs comparing relatives with different shared DNA or upbringing to estimate genetic vs. environmental influence.
Heredity & Env.
Central nervous system (CNS)
The brain and spinal cord — the body's central command center.
Nervous System
Peripheral nervous system (PNS)
Nerves outside the CNS relaying signals between the brain/spinal cord and the rest of the body.
Nervous System
Autonomic nervous system
Controls involuntary processes; split into sympathetic (arousing) and parasympathetic (calming) branches.
Nervous System
Somatic nervous system
Controls voluntary movement of skeletal muscles.
Nervous System
Neuron
Basic cell of the nervous system — dendrites receive, axon sends, terminal buttons release neurotransmitters.
Neuron
Action potential
Brief electrical impulse traveling down a neuron's axon when it fires.
Neuron
Synapse
Tiny gap between neurons where neurotransmitters cross to enable chemical communication.
Neuron
Neurotransmitter
Chemical messenger (dopamine, serotonin, GABA, acetylcholine) released at the synapse.
Neuron
Reuptake
Reabsorption of neurotransmitters by the sending neuron after crossing the synapse; targeted by SSRIs.
Neuron
Endocrine system
Network of glands releasing hormones into the bloodstream — slower than neural signals but longer-lasting.
Brain & Body
Cerebral cortex
Wrinkled outer layer of the brain responsible for higher functions — thinking, planning, language, perception.
Brain
Frontal lobe
Brain region handling planning, decision-making, voluntary movement (motor cortex), and personality.
Brain
Hippocampus
Seahorse-shaped structure critical for forming new long-term memories.
Brain
Amygdala
Almond-shaped structure processing emotions, especially fear and aggression.
Brain
Cerebellum
Structure coordinating voluntary movement, balance, and motor learning.
Brain
Plasticity
The brain's ability to reorganize itself by forming new neural connections — greatest early in life but lifelong.
Brain
Sleep stages (NREM/REM)
Sleep cycles including deeper NREM stages and REM sleep — where vivid dreams occur and the body is largely paralyzed.
Sleep
Circadian rhythm
Roughly 24-hour internal biological clock regulating the sleep-wake cycle and other daily processes.
Sleep
Absolute threshold
Minimum stimulus intensity detectable 50% of the time.
Sensation
Sensory adaptation
Reduced sensitivity to a constant stimulus over time.
Sensation
Transduction
Conversion of physical sensory energy into neural signals the brain can process.
Sensation
Sensation vs. perception
Sensation: detecting raw stimuli. Perception: the brain's interpretation and organization of those stimuli.
Sensation
Big Idea 1
All behavior has a biological basis
Every thought, feeling, and action is grounded in the activity of your nervous system. Genes, neurons, neurotransmitters, hormones, and brain structures all interact to produce behavior — making psychology a biological science at its core.
BiologyFoundations
Big Idea 2
Heredity and environment interact — it's never just one
AP Psychology replaces the old nature-vs.-nurture debate with a more accurate view: genes set predispositions, but the environment shapes how those predispositions develop. Twin and adoption studies show both factors at work in nearly every trait.
Nature & NurtureGenes
Big Idea 3
Neurons communicate through electrochemical signals
When a neuron fires, an electrical action potential travels down its axon and triggers the release of neurotransmitters into the synapse. These chemicals influence whether the next neuron fires — small changes in this process shape mood, learning, and behavior.
NeuronsNeurotransmitters
Big Idea 4
The brain is specialized but also remarkably plastic
Different regions handle different functions — the frontal lobe for planning, the hippocampus for memory, the amygdala for emotion — but the brain can also reorganize itself after injury or with learning. Plasticity is greatest early in life but never fully disappears.
BrainPlasticity
Big Idea 5
Sleep is biologically essential, not optional
The circadian rhythm and the sleep cycle actively support memory consolidation, emotional regulation, and physical health. Disruptions like insomnia, narcolepsy, and sleep apnea have measurable consequences for thinking and well-being.
SleepWellness
Big Idea 6
Sensation is biological; perception is psychological
Sensation is the conversion of physical energy into neural signals (transduction). Perception is the brain's active interpretation of those signals, shaped by attention, expectation, and context — the same input can produce different experiences.
SensationPerception