AP Psychology Unit 1 Cheatsheet: Biological Bases of Behavior

Start with the first 3 sections of the Unit 1 one-page cheatsheet below. The full sheet is a PDF you can print.

1.1 Heredity × Environment

Behavior and mental processes result from interaction between heredity (genetic predispositions) and environment (family, culture, education, experience).
Evolutionary perspective: natural selection favors traits that increase survival/reproductive success; beware deterministic or discriminatory misuse such as eugenics.
Twin, family, and adoption studies compare biological relatedness and shared environments; they show influence, not that one factor acts alone.

Outside scope: genotype/phenotype, DNA/chromosome mechanics, dominant/recessive expression.

1.2 Nervous-System Map

Nervous system → CNS (brain + spinal cord) and PNS

PNS division	Job
Somatic	Voluntary skeletal movement; sensory/motor messages.
Autonomic	Involuntary organs and glands.
Sympathetic	Arouses: fight-or-flight; mobilizes energy.
Parasympathetic	Calms: rest-and-digest; conserves energy.

1.3 Neurons, Signaling + Drugs

Neurons transmit information; glia provide structure, insulation, communication, and waste transport.
Reflex arc: sensory neuron → spinal interneuron → motor neuron; response can occur before brain processing.

resting potential → threshold → all-or-none depolarization → refractory period → neurotransmitter release → receptor binding → reuptake/breakdown

Excitatory messages make firing more likely; inhibitory messages make it less likely.
Agonist increases/mimics action; antagonist blocks/reduces; reuptake inhibitor leaves more transmitter in synapse.

Neurotransmitter	High-value association
Dopamine	reward, movement, learning
Serotonin	mood, sleep
Norepinephrine	alertness, arousal
Glutamate / GABA	major excitatory / inhibitory
Endorphins / substance P	pain relief / pain signaling
Acetylcholine	muscle action, learning, memory

Hormones: adrenaline—arousal; leptin—satiety; ghrelin—hunger; melatonin—sleep timing; oxytocin—bonding. Drug classes: stimulants ↑ activity; depressants ↓; hallucinogens distort perception/cognition; opioids relieve pain. Repeated use can produce tolerance, addiction, and withdrawal.

The rest of the Unit 1 sheet

6 more sections are on the one-page PDF:

1.4 Brain Structures + Methods
1.5 Sleep
1.6 Sensation Basics
Vision + Hearing
Chemical + Body Senses
High-Frequency Confusions

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