AP Psychology Unit 1: Biological Bases of Behavior 2025/2026

Heredity

The passing of genetic traits from parents to offspring

Environmental Factors

External factors that one experiences that influence physical, behavioral, and mental traits and processes.

Evolutionary Perspective

Psychological approach that explores how natural selection effects the expression of behavior and mental.

Eugenics

A pseudo-science that applies the evolutionary perspective in ways that discriminate against others

Sympathetic Nervous System

the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations

Parasympathetic Nervous System

the division of the autonomic nervous system that calms the body, conserving its energy. A reversal of the effects of the sympathetic nervous system.

The Central Nervous System

Consists of the brain and spinal cord

Endocrine System

The body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream

Endocrine Glands

Glands that secrete hormones directly into the bloodstream

Neuron

A nerve cell; the basic building block of the nervous system; sends and receives signals that affect many aspects of behavior and motor function; also present in the brain to send and receive information

Glial Cells

Cells in the nervous system that support, nourish, and protect neurons

Sensory Neurons

Neurons that carry incoming information from the sensory receptors to the brain and spinal cord

Motor Neurons

Neurons that carry outgoing information from the brain and spinal cord to the muscles and glands

Interneurons

Neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs

Effector

An organ or cell that acts in response to a stimulus.

Receiver

Appendage that sends sensory information via neurons

Reflex

A simple, automatic, inborn response to a sensory stimulus, such as the knee-jerk response.

Refractory Period

A period of inactivity after a neuron has fired

All or Nothing Principle

The principle that once the electrical impulse reaches a certain level of intensity (its threshold), it fires and moves all the way down the axon without losing any intensity.

Depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

Resting Potential

The state of the neuron when not firing a neural impulse

Reuptake

A neurotransmitter's reabsorption by the sending neuron

Threshold

The level of stimulation required to trigger a neural impulse

Excitatory Transmission

Neurotransmitter transmission that makes an action potential more likely.

Inhibitory Transmission

Neurotransmitter transmission that makes an action potential less likely

Acetylcholine (ACh)

A neurotransmitter that enables learning and memory and also triggers muscle contraction. Associated with Alzheimer's

Glutamate

A major excitatory neurotransmitter; involved in memory, sensory, and motor function.

Dopamine

A neurotransmitter associated with movement, attention and learning and the brain's pleasure and reward system. Associated with Parkinson's.

Norepinephrine

A neurotransmitter that governs sympathetic arousal by activating the heart and blood vessels; neurotransmitter responsible for the "fight or flight" sensation

Serotonin

Neurotransmitter that affects mood, hunger, sleep, and arousal

Endorphins

Natural, opiate-like neurotransmitters linked to pain control and to pleasure

Substance P

A neurotransmitter that is involved in the transmission of pain messages to the brain.

Dendrite

The bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body

Cell Body

Contains nucleus and organelles of neuron.

Nucleus

Organelle that maintains the cell and keep the neuron functional.

Axon

The extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

Myelin Sheath

A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next.

Shawnn Cell

A special type of glial cell that produces myelin sheath

Nodes of Ranvier

Gaps in the myelin sheath to which voltage-gated sodium channels are confined.

Axon Terminal

The endpoint of a neuron where neurotransmitters are stored

Adrenaline

A hormone released into the bloodstream in response to physical or mental stress.

Leptin

A hormone produced by adipose (fat) cells that acts as a satiety factor in regulating appetite.

Ghrelin

Hormone secreted by empty stomach; sends "I'm hungry" signals to the brain

Melatonin

A hormone manufactured by the pineal gland that produces sleepiness.

Oxytocin

Hormone, often called the "love hormone," released by the pituitary gland that fosters social bonding, trust, empathy, and attachment

Pituitary Gland

The endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.

Pineal Gland

The gland that secretes melatonin

Hypothalamus

A neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion

Thyroid Gland

Produces hormones that regulate metabolism, body heat, and bone growth

Adrenal Gland

A pair of endocrine glands that sit just above the kidneys and secrete adrenaline that help arouse the body in times of stress.

Pancreas

Regulates the level of sugar in the blood

Testes/Ovaries (Gonads)

Primary sex organs

Agonist

A substance that increases neural firing

Anatagonist

A substance that discourages neural firing

Reuptake Inhibitors

A Substance that blocks the reabsorption of neurotransmitters.

Stimulants

Drugs (such as caffeine, nicotine, and the more powerful amphetamines, cocaine, and Ecstasy) that excite neural activity and speed up body functions.

Depressants

Drugs (such as alcohol, barbiturates, and opiates) that reduce neural activity and slow body functions

Hallucinogens

psychedelic ("mind-manifesting") drugs, such as LSD, that distort perceptions and evoke sensory images in the absence of sensory input

Opioids

Such as heroin; typically used as pain relivers

The Medulla

An extension of the spinal cord into the skull that coordinates heart rate, circulation, and respiration

Reticular Activating System

Controls some voluntary movement, eye movement, and some types of learning, cognition, and emotion

Cerebellum

A large structure of the hindbrain that controls fine motor skills.

Thalamus

The brain's sensory control center, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

Amygdala

Critical for processing information with emotional content, such as understanding facial expressions

Hippocampus

A neural center located in the limbic system that helps process explicit memories for storage.

Gyri

Elevated ridges in the brain

Sulei

Grooves in the brain

Fissures

A lager version of sulei

Occipital Lobes

Portion of the cerebral cortex lying at the back of the head; includes areas that receive information from the visual fields

Somatosensory Region

The part of the sensory system dealing with reception in the body wall and limbs; receives inputs from exteroceptors, proprioceptors, and interceptors

Motor Cortex

An area at the rear of the frontal lobes that controls voluntary movements

Auditory Cortex

The area of the temporal lobe responsible for processing sound information

Temporal Cortex

Brain region that is important for understanding written and spoken language.

Wernicke's Area

A brain area involved in language comprehension and expression.

Wernicke's Aphasia

Condition resulting from damage to Wernicke's area, causing the affected person to be unable to understand or produce meaningful language

Broca's Area

Controls language expression - an area of the frontal lobe, usually in the left hemisphere, that directs the muscle movements involved in speech.

Broca's Aphasia

Condition resulting from damage to Broca's area, causing the affected person to be unable to speak fluently, to mispronounce words, and to speak haltingly

Circadian Rhythm

the biological clock; regular bodily rhythms (for example, of temperature and wakefulness) that occur on a 24-hour cycle

Non-REM Stage 1 and 2 Sleep

Light Sleep

Non-REM Stage 3 Sleep

Deep Sleep

REM Sleep

Rapid eye movement sleep, a recurring sleep stage during which vivid dreams commonly occur. Also known as paradoxical sleep, because the muscles are relaxed (except for minor twitches) but other body systems are active.

Activation-Synthesis Theory

Theory that dreams reflect inputs from brain activation originating in the pons, which the forebrain then attempts to weave into a story

Consolidation Theory

The theory that sleep helps strengthen the neural connections that form our memories.

Sleep Apnea

A sleep disorder characterized by temporary cessations of breathing during sleep and repeated momentary awakenings

REM Sleep Disorder

A neurological disorder in which the person does not become paralyzed during REM sleep and thus acts out dreams

Narcolepsy

A sleep disorder characterized by uncontrollable sleep attacks. The sufferer may lapse directly into REM sleep, often at inopportune times.

Somnambulism

Sleepwalking

Insomnia

Difficulty in falling asleep or staying asleep

Reticular Formation

Regulates the transition between sleep and wakefulness

Pons

A brain structure that helps initiate REM sleep

Retina

The light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information

Blind Spot

Where the visual nerve exits the eye

Prosopagnosia

Caused by damage to the occipital lobes and characterized by the inability to recognize faces

Place Theory

In hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated

Frequency Theory

In hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch

Volley Theory

A theory that proposes that our brain decodes pitch by noticing the frequency at which groups of hair cells on the basilar membrane are firing

Conductive Deafness

Hearing loss caused by damage to the middle ear, thus interfering with the transmission of sound waves to the cochlea

Sensorineural Deafness

Deafness that results from damage to the auditory nerve

Pheromones

Odorless chemicals that serve as social signals to members of one's species

Gustation

Sense of taste