AP Psychology: Biological Bases of Behavior (High School)

What is the function of dendrites?

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

What is the soma (cell body) and what does it do?

Answer: The part of the neuron containing the nucleus; it integrates incoming signals from the dendrites and sustains the cell's life.

What is the axon, and what is the myelin sheath?

Answer: The axon is the extension that carries the neural impulse away from the cell body to other neurons/muscles/glands. The myelin sheath is a fatty layer of tissue segments that insulates the axon and speeds up neural transmission.

What are Nodes of Ranvier and why do they matter?

Answer: Small gaps between segments of the myelin sheath where the impulse 'jumps' from node to node (saltatory conduction), greatly increasing conduction speed.

What is a synapse, and what is the synaptic gap?

Answer: The junction between the axon terminal of a sending neuron and the dendrite/body of a receiving neuron; the synaptic gap (cleft) is the tiny fluid-filled space neurotransmitters cross to reach the receiving neuron.

Describe the neuron's resting potential.

Answer: About -70 mV; the inside of the neuron is negatively charged relative to the outside because of the distribution of ions (more Na+ outside, more K+ and negative protein ions inside), maintained by the sodium-potassium pump.

What happens when stimulation reaches the threshold (~-55 mV)?

Answer: Sodium (Na+) channels open, Na+ rushes into the axon, and the neuron depolarizes (becomes momentarily positive inside) — this triggers the action potential.

What is the all-or-none principle?

Answer: A neuron either fires a full action potential or it does not fire at all; the strength of the stimulus doesn't change the size of the impulse, only the firing rate.

Describe repolarization and the refractory period.

Answer: After depolarization, K+ channels open and K+ flows out, restoring the negative charge inside (repolarization). During the refractory period that follows, the neuron cannot fire again until it resets to resting potential.

How is a neurotransmitter's action in the synapse ended?

Answer: Either through reuptake (the sending neuron reabsorbs excess neurotransmitter) or enzymatic degradation (enzymes break the neurotransmitter down in the synaptic gap).

Distinguish an agonist from an antagonist.

Answer: An agonist is a molecule that mimics a neurotransmitter and increases its action at the receptor; an antagonist blocks or inhibits a neurotransmitter's normal effect at the receptor.

Acetylcholine (ACh): function and disorder link

Answer: Enables muscle action, learning, and memory. Undersupply is linked to Alzheimer's disease.

Dopamine: function and disorder links

Answer: Influences movement, learning, attention, and emotion. Oversupply linked to schizophrenia; undersupply linked to Parkinson's disease (and to addiction/reward pathways).

Serotonin: function and disorder link

Answer: Affects mood, hunger, sleep, and arousal. Undersupply linked to depression.

Norepinephrine: function

Answer: Helps control alertness and arousal; undersupply can depress mood.

GABA: function and disorder link

Answer: The major inhibitory neurotransmitter in the CNS; undersupply linked to seizures, tremors, and insomnia.

Glutamate: function and disorder link

Answer: The major excitatory neurotransmitter, important in memory; oversupply can overstimulate the brain, producing migraines or seizures.

Endorphins: function

Answer: Natural opiate-like neurotransmitters that reduce pain and produce feelings of pleasure/well-being.

Distinguish the CNS from the PNS.

Answer: Central Nervous System (CNS) = brain and spinal cord. Peripheral Nervous System (PNS) = all other nerves connecting the CNS to the rest of the body.

Distinguish the somatic and autonomic nervous systems.

Answer: Somatic nervous system controls voluntary movements of skeletal muscles. Autonomic nervous system controls involuntary/automatic functions of internal organs and glands.

Distinguish the sympathetic and parasympathetic nervous systems.

Answer: Sympathetic nervous system arouses the body for action (fight-or-flight: increases heart rate, releases stress hormones). Parasympathetic nervous system calms the body (rest-and-digest: slows heart rate, conserves energy).

What is the endocrine system and how does it differ from neural communication?

Answer: A system of glands that secretes hormones directly into the bloodstream; hormone messages travel slower than neural impulses but their effects last longer.

What is the pituitary gland and why is it called the 'master gland'?

Answer: A pea-sized gland at the base of the brain that, under control of the hypothalamus, releases hormones that regulate growth and trigger other endocrine glands to secrete their hormones.

What do the adrenal glands do?

Answer: Sit atop the kidneys; release epinephrine (adrenaline) and norepinephrine, which increase heart rate, blood pressure, and blood sugar to prepare the body for the stress response.

What is the HPA axis?

Answer: The hypothalamus-pituitary-adrenal axis: the hypothalamus signals the pituitary, which signals the adrenal glands, to coordinate the body's stress response.

What do the medulla and pons do (brainstem)?

Answer: Medulla: controls heartbeat and breathing. Pons: helps coordinate movements and control sleep; both sit atop the spinal cord.

What is the reticular formation?

Answer: A nerve network running through the brainstem that plays an important role in controlling arousal and attention.

What is the thalamus's function?

Answer: The brain's sensory relay station, located atop the brainstem; it directs incoming sensory messages (except smell) to the appropriate cortical areas.

What is the cerebellum's function?

Answer: Located at the rear of the brainstem; coordinates voluntary movement, balance, and helps process procedural (implicit) memory.

What is the limbic system?

Answer: A neural system (including the hippocampus, amygdala, and hypothalamus) located below the cerebral hemispheres, associated with emotions and drives such as fear and aggression.

What is the hippocampus's role?

Answer: A limbic system structure that processes conscious (explicit) memories for storage.

What is the amygdala's role?

Answer: Two lima-bean-sized limbic structures linked to emotion, particularly fear and aggression.

What is the hypothalamus's role?

Answer: A limbic structure that maintains homeostasis (hunger, thirst, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward.

Frontal lobe: location and functions

Answer: Located behind the forehead; involved in speaking, muscle movements (motor cortex), making plans, judgments, decision-making, and personality.

Parietal lobe: location and functions

Answer: Located at the top/rear of the head; includes the somatosensory cortex, which registers and processes touch, temperature, and body position sensations.

Occipital lobe: location and function

Answer: Located at the back of the head; contains the visual cortex and receives/processes visual information.

Temporal lobe: location and functions

Answer: Located above the ears; includes the auditory cortex (processes sound) and Wernicke's area (language comprehension).

Distinguish the motor cortex from the somatosensory cortex.

Answer: Motor cortex (rear of frontal lobe) controls voluntary movements. Somatosensory cortex (front of parietal lobe) processes body sensations like touch and pressure. Both are mapped in proportion to body part sensitivity/control, not actual size.

How are the brain's two hemispheres specialized?

Answer: The left hemisphere typically dominates language, logic, and analytical processing; the right hemisphere typically dominates spatial perception, creativity, and holistic processing.

What is the corpus callosum and what happens if it's cut?

Answer: The large band of neural fibers connecting the two hemispheres. Cutting it (split-brain surgery, historically used to treat severe epilepsy) prevents the hemispheres from directly communicating.

What did split-brain research (Sperry & Gazzaniga) reveal?

Answer: When information was presented to only one hemisphere of a split-brain patient (e.g., an image to the left visual field/right hemisphere), the person couldn't verbally name it (since language is in the left hemisphere) but could still select/point to the matching object with the left hand, showing the hemispheres can function independently.

What does an EEG measure?

Answer: Electroencephalogram: records electrical activity (brain waves) of neurons via scalp electrodes; used to study sleep stages and overall brain activity.

Distinguish MRI from fMRI.

Answer: MRI uses magnetic fields and radio waves to produce detailed images of brain structure. fMRI (functional MRI) measures blood flow/oxygen use to reveal brain function and activity in real time.

What does a PET scan measure?

Answer: Positron Emission Tomography tracks a radioactive form of glucose to show which brain areas are metabolically active (using more energy) during a given task.

What is neuroplasticity?

Answer: The brain's ability to change and reorganize itself by forming new neural connections, especially in response to learning or damage.

What is heritability?

Answer: The proportion of variation among individuals in a population that can be attributed to genes, rather than environment.

How do twin and adoption studies help separate nature and nurture?

Answer: Researchers compare trait similarity between identical twins (share 100% of genes) and fraternal twins (share ~50%), and between adopted children and both biological and adoptive parents, to estimate genetic vs. environmental contributions.

What is the evolutionary psychology perspective?

Answer: Explains behavior and mental processes by how natural selection favored traits/behaviors that enhanced survival and reproductive success, passed on through genes.

What is a circadian rhythm?

Answer: The roughly 24-hour biological clock that regulates the cycle of sleep and wakefulness (and other bodily rhythms), influenced by light exposure.

Describe NREM sleep stages N1–N3.

Answer: N1: light sleep, hypnagogic sensations (falling, floating); N2: deeper sleep with sleep spindles and K-complexes; N3: deep slow-wave sleep, hardest to wake from, important for physical restoration.

What characterizes REM sleep?

Answer: 'Paradoxical sleep' with rapid eye movements, high brain activity resembling wakefulness, vivid dreaming, and temporary muscle paralysis (atonia).

How does sleep architecture change across a typical night?

Answer: Sleep cycles through NREM stages N1→N2→N3 and back, then into REM, roughly every 90 minutes; early cycles have more N3 (deep sleep), while REM periods lengthen as the night progresses.

Compare Freud's and the activation-synthesis theory of dreaming.

Answer: Freud: dreams have manifest content (storyline we remember) and latent content (hidden, symbolic meaning fulfilling wishes). Activation-synthesis theory: dreams result from the brain synthesizing and interpreting random neural activity during REM sleep, without inherent hidden meaning.

What is insomnia?

Answer: A sleep disorder involving persistent difficulty falling or staying asleep.

What is narcolepsy?

Answer: A sleep disorder characterized by uncontrollable sleep attacks and sudden lapses into REM sleep during waking hours, often with cataplexy (sudden muscle weakness).

What is sleep apnea?

Answer: A disorder in which a person repeatedly stops breathing during sleep, often resulting in fragmented sleep and daytime fatigue.

Distinguish night terrors from nightmares.

Answer: Night terrors occur during N3 (deep NREM sleep), involve intense fear, screaming, and autonomic arousal with no memory of the episode. Nightmares occur during REM sleep and are typically remembered.

What is somnambulism?

Answer: Sleepwalking; occurs during N3 deep sleep, more common in children.

What are depressants and give examples.

Answer: Psychoactive drugs that slow down neural/bodily activity (e.g., alcohol, barbiturates, opioids); they can reduce anxiety and impair judgment/memory, and depress respiration at high doses.

What are stimulants and give examples.

Answer: Psychoactive drugs that excite neural activity and speed up body functions (e.g., caffeine, nicotine, amphetamines, cocaine); increase energy and elevate mood.

What are hallucinogens and give examples.

Answer: Psychedelic drugs that distort perceptions and evoke sensory images without sensory input (e.g., LSD, marijuana/THC).

Distinguish tolerance, withdrawal, and physical vs. psychological dependence.

Answer: Tolerance: needing larger doses for the same effect. Withdrawal: discomfort/craving when stopping use. Physical dependence: body requires the drug to avoid withdrawal symptoms. Psychological dependence: craving the drug for emotional/mental reasons without a physiological need.