AP Psychology Unit 1: Biological Bases of Behavior and Sleep

A comprehensive vocabulary review of AP Psychology biological bases of behavior, brain anatomy, biological rhythms, sleep disorders, dream theories, and psychoactive drug classes.

Neuron

The basic building block of the nervous system; a nerve cell specialized in receiving, processing, and transmitting information.

Dendrites

Bushy, branching extensions of a neuron that receive messages from other cells and conduct impulses toward the cell body.

Axon

The long extension of a neuron ending in branching terminal fibers that passes messages away from the cell body to other neurons, muscles, or glands.

Myelin sheath

A layer of fatty tissue segmentally encasing the fibers of many neurons that insulates the axon and speeds neural transmission; degeneration leads to Multiple Sclerosis.

Glial cells

Cells in the nervous system that support, nourish, and protect neurons, while also contributing to learning, thinking, and memory.

Terminal branches

The branched ends of an axon containing vesicles that store neurotransmitters and form junctions with other cells.

Synapse

The junction or microscopic gap (synaptic cleft) between the axon terminal of the sending neuron and the dendrite or cell body of the receiving neuron.

Action potential

A brief electrical charge that travels down an axon, generated by the movement of positively charged ions across the cell membrane.

All-or-nothing response

The principle that a neuron fires completely or does not fire at all; stimulus strength increases firing frequency rather than impulse strength.

Refractory period

A brief resting pause after a neuron fires during which subsequent action potentials cannot occur until resting membrane potential is restored.

Neurotransmitters

Chemical messengers released by the sending neuron that cross the synaptic gap to bind to matching receptor sites on the receiving neuron.

Reuptake

The reabsorption process by which excess neurotransmitters in the synaptic gap are taken back into the sending neuron's terminal branches.

Neurotransmitter receptors

Protein molecules on the postsynaptic membrane specifically shaped to bind with incoming chemical messengers in a lock-and-key fashion.

Excitatory vs. inhibitory signals

Excitatory signals stimulate the neuron to trigger an action potential (accelerator), whereas inhibitory signals decrease the likelihood of firing (brakes).

Agonist vs. antagonist

An agonist binds to a receptor site to mimic or amplify neurotransmitter effects, while an antagonist binds to block and inhibit neurotransmitter action.

Acetylcholine (ACh)

A neurotransmitter enabling muscle action, learning, and memory; deterioration of producing neurons is linked to Alzheimer's disease.

Dopamine

A neurotransmitter influencing movement, learning, attention, and emotion; excess is linked to schizophrenia, while undersupply leads to Parkinson's tremors.

Serotonin

A neurotransmitter regulating mood, hunger, sleep, and arousal; deficits are linked to depression, while dangerous excess causes serotonin syndrome.

Norepinephrine

A neurotransmitter controlling alertness and physical arousal; deficits can depress mood, while excess triggers anxiety and hypertension.

GABA (gamma-aminobutyric acid)

The primary inhibitory neurotransmitter in the brain; an undersupply is linked to seizures, tremors, and insomnia.

Glutamate

The primary excitatory neurotransmitter involved in memory; an oversupply overstimulates the brain, causing migraines or seizures.

Endorphins

Opiate-like neurotransmitters linked to pain control and pleasure; an undersupply causes hypersensitivity to pain.

Central nervous system (CNS)

The primary decision-making component of the nervous system, consisting of the brain and spinal cord.

Peripheral nervous system (PNS)

The sensory and motor neurons connecting the central nervous system to the rest of the body.

Somatic vs. autonomic nervous system

The somatic system directs voluntary movements of skeletal muscles, whereas the autonomic system regulates involuntary actions of internal organs and glands.

Sympathetic vs. parasympathetic nervous system

The sympathetic branch mobilizes the body during fight-or-flight emergencies, while the parasympathetic branch calms the body during rest-and-digest states.

Sensory vs. motor neurons

Sensory (afferent) neurons carry inward information to the CNS, whereas motor (efferent) neurons transport outward commands from the CNS to tissues.

Spinal reflex

An automatic response to a stimulus routed through sensory neurons, interneurons, and motor neurons inside the spinal cord prior to brain processing.

Endocrine system

The body's slower chemical communication network, consisting of glands that secrete hormones directly into the bloodstream.

Hormones

Chemical messengers synthesized by endocrine glands that circulate through the bloodstream and produce longer-lasting physiological effects.

Cortisol

The primary glucocorticoid stress hormone released by adrenal glands to elevate blood glucose and modulate immune functions during stress.

Pituitary gland

The endocrine system's master gland regulated by the hypothalamus, responsible for governing other glands and releasing growth hormone and oxytocin.

Growth hormone and oxytocin

Hormones secreted by the pituitary gland; one promotes physical growth while the other enables contractions, milk ejection, and social bonding.

Electroencephalogram (EEG)

A neuroimaging method recording electrical wave activity across the brain's surface via scalp electrodes, commonly applied in sleep and seizure research.

Functional MRI (fMRI)

A neuroimaging technique detecting blood flow and metabolic activity through successive MRI scans to reveal both structure and real-time function.

Brainstem

The central core and oldest evolutionary region of the brain, starting where the spinal cord swells into the skull, directing automatic survival functions.

Medulla

The base region of the brainstem controlling vital involuntary autonomic functions, including heartbeat and respiration.

Thalamus

The central sensory routing hub positioned atop the brainstem, relaying incoming sensory signals (except smell) to cortical processing centers.

Reticular formation

A nerve pathway extending from the brainstem into the thalamus that plays a fundamental role in controlling arousal and wakefulness.

Cerebellum

The rear hindbrain structure coordinating voluntary movements, physical balance, fine motor control, and nonverbal procedural memory.

Limbic system

A neural network beneath the cerebral hemispheres containing the amygdala, hypothalamus, and hippocampus, associated with emotions and basic drives.

Amygdala

Two neural clusters in the limbic system centrally involved in emotional processing, particularly fear responses and aggressive behaviors.

Hypothalamus

A limbic structure below the thalamus coordinating bodily maintenance drives (hunger, thirst, body temperature), reward systems, and the endocrine system.

Hippocampus

A limbic system component essential for processing and consolidating conscious, explicit memories before long-term cortical storage.

Cerebral cortex

The outermost neural tissue layer covering the cerebral hemispheres, functioning as the ultimate control and information-processing center.

Frontal lobe

The cortical area behind the forehead governing executive functioning, motor movement, speech expression, and abstract decision-making.

Motor cortex

A strip situated at the posterior edge of the frontal lobe that controls voluntary muscular movements.

Broca’s area

A left frontal lobe region directing the physical muscle movements required for expressive speech production.

Parietal lobe

The cortical area positioned at the top-rear of the skull that receives and interprets sensory information regarding tactile touch and body position.

Somatosensory cortex

A strip at the anterior edge of the parietal lobe that registers and processes bodily touch sensations and movement feedback.

Temporal lobe

The lateral region of the cerebral cortex situated above the ears containing primary auditory processing fields.

Wernicke’s area

A cortical structure typically located in the left temporal lobe essential for language comprehension and meaningful expression.

Occipital lobe

The cortical region situated at the posterior base of the skull containing visual reception and interpretation centers.

Association areas

Non-primary sensory or motor cortical regions dedicated to higher-order mental tasks such as interpreting, planning, and contextual reasoning.

Neuroplasticity

The capacity of neural circuits to adapt and reorganize structurally following brain injury or through novel environmental experiences.

Corpus callosum

The dense transverse band of neural axons bridging the two cerebral hemispheres to enable interhemispheric communication.

Split brain

A clinical condition caused by severing the corpus callosum to alleviate severe epilepsy, demonstrating hemispheric lateralization of cognitive faculties.

Circadian rhythm

The intrinsic 24-hour biological cycle governing physiological patterns such as body temperature and sleep-wake schedules.

Sleep stages and brain waves

Alert waking (beta waves), relaxed resting (alpha waves), NREM-1 (theta waves / hypnagogic sensations), NREM-2 (sleep spindles / K-complexes), NREM-3 (delta waves), and REM (rapid sawtooth waves).

REM vs. NREM sleep

REM entails paradoxical sleep marked by vivid dreams and motor paralysis alongside high internal arousal; NREM represents all non-REM sleep stages.

REM rebound

The compensatory increase in the frequency and duration of REM sleep episodes following periods of prior REM sleep deprivation.

Insomnia

A persistent sleep disorder involving recurring difficulty with initiating sleep or maintaining unbroken sleep.

Narcolepsy

A neurological sleep disorder marked by sudden uncontrollable sleep attacks where individuals lapse directly into REM sleep.

Sleep apnea

A sleep disorder involving repeated cessations of respiration during sleep resulting in frequent micro-arousals and oxygen desaturation.

Somnambulism

The clinical diagnostic designation for sleepwalking, an episode typically arising during stage NREM-3 deep sleep.

REM sleep behavior disorder

A sleep disturbance where normal motor atonia during REM sleep fails, causing individuals to physically act out dream scenarios.

Activation-synthesis theory

The hypothesis that dreams represent the cortex's attempt to synthesize and construct meaning from spontaneous brainstem neural activity during REM.

Consolidation theory

The hypothesis proposing that sleep serves to reorganize, consolidate, and stabilize experiences into permanent long-term memory.

Psychoactive drugs

Chemical compounds that cross the blood-brain barrier to alter sensory perceptions, mood, and cognitive functioning.

Tolerance vs. addiction

Tolerance is neuroadaptation requiring higher doses to produce the target effect, while addiction involves compulsive usage despite negative fallout.

Depressants

Psychoactive agents such as alcohol, barbiturates, and opiates that reduce overall neural activity and depress central bodily operations.

Stimulants

Psychoactive substances including caffeine, cocaine, and nicotine that elevate neural firing and accelerate physiological processes.

Hallucinogens

Psychoactive drugs like LSD and THC that induce vivid perceptual distortions and sensory impressions without external stimuli.