Biological Bases of Behavior: every key term you need (+ practice quiz)

More AP Psychology guides

• Scientific Foundations of Psychology
• Sensation and Perception
• Learning
• Cognitive Psychology
• Developmental Psychology

Neuron

The basic cell of the nervous system that receives, processes, and transmits electrochemical signals.

Dendrites

Branchlike extensions that receive incoming messages and conduct impulses toward the cell body.

Axon

The extension that carries neural impulses away from the cell body toward other neurons or muscles.

Myelin Sheath

A fatty layer insulating the axon that speeds neural transmission; its breakdown causes multiple sclerosis.

Action Potential

A brief electrical charge that travels down the axon when a neuron fires; operates all-or-none.

Resting Potential

The negative charge (about -70 mV) inside a neuron when it is not firing, ready to be triggered.

All-or-None Principle

A neuron either fires at full strength or not at all; stimulus intensity affects rate, not size, of firing.

Synapse

The tiny gap between neurons across which neurotransmitters diffuse to relay messages.

Neurotransmitters

Chemical messengers released into the synapse that bind to receptors on the next neuron.

Reuptake

The reabsorption of excess neurotransmitters by the sending neuron; blocked by many antidepressants.

Dopamine

Neurotransmitter influencing movement, reward, and attention; excess linked to schizophrenia, lack to Parkinson's.

Serotonin

Neurotransmitter affecting mood, sleep, and appetite; low levels are linked to depression.

Acetylcholine

Neurotransmitter enabling muscle action and memory; its loss is associated with Alzheimer's disease.

Central Nervous System

The brain and spinal cord; processes information and directs the body's responses.

Peripheral Nervous System

All nerves outside the CNS; includes the somatic and autonomic divisions.

Autonomic Nervous System

Controls involuntary functions; its sympathetic branch arouses ('fight or flight') and parasympathetic calms.

Medulla

Brainstem structure that controls vital reflexes such as heartbeat and breathing.

Cerebellum

'Little brain' at the rear that coordinates voluntary movement, balance, and some learning.

Amygdala

Limbic structure central to fear, aggression, and emotional responses.

Hippocampus

Limbic structure essential for forming new explicit (conscious) memories.

Hypothalamus

Regulates hunger, thirst, body temperature, and links the nervous system to the endocrine system.

Cerebral Cortex & Lobes

Wrinkled outer layer of higher thought; four lobes: frontal, parietal, temporal, occipital.

Endocrine System

Network of glands that secrete hormones into the bloodstream; the pituitary is the 'master gland.'

Neuroplasticity

The brain's ability to reorganize and form new connections, especially after damage or learning.

Action Potential

A brief electrical charge that travels down the axon when depolarization reaches threshold; sodium ions rush in, then potassium flows out.

All-or-None Principle

A neuron either fires at full strength or not at all; stronger stimuli increase the rate of firing, not the size of the impulse.

Refractory Period

Brief interval after an action potential during which the neuron cannot fire again while it resets its ion balance.

Reuptake

The sending neuron reabsorbs excess neurotransmitter from the synapse; SSRIs block serotonin reuptake, leaving more in the synapse.

Agonist vs Antagonist

An agonist mimics or boosts a neurotransmitter's effect (e.g., morphine at endorphin receptors); an antagonist blocks it (e.g., curare at ACh receptors).

Glutamate & GABA

Glutamate is the brain's main excitatory neurotransmitter (memory); GABA the main inhibitory one (calming; alcohol and benzodiazepines enhance it).

Sympathetic vs Parasympathetic

Sympathetic arouses (fight-or-flight: heart rate up, digestion down); parasympathetic calms and conserves energy afterward.

Reflex Arc

A simple automatic response handled by the spinal cord via sensory neuron → interneuron → motor neuron, before the brain is involved.

Hippocampus

Limbic structure that forms new explicit memories; damage (as in patient H.M.) causes anterograde amnesia.

Amygdala

Two limbic clusters linked to fear and aggression; lesions reduce fear responses, stimulation provokes rage or fear.

Hypothalamus

Directs maintenance activities (hunger, thirst, temperature, sexual behavior), governs the pituitary, and contains reward centers.

Broca's vs Wernicke's Area

Broca's (left frontal) controls speech production — damage causes halting speech; Wernicke's (left temporal) handles comprehension — damage yields fluent but meaningless speech.

Split-Brain Research

Sperry and Gazzaniga: after corpus callosum severing, a word flashed to the left visual field (right hemisphere) can be drawn with the left hand but not named.

Neuroplasticity

The brain's ability to reorganize after damage or experience, especially in childhood; e.g., blind people's visual cortex processing touch/Braille.

fMRI vs EEG vs PET

fMRI shows blood-flow changes (function + structure); EEG records electrical waves (fast timing); PET tracks radioactive glucose consumption.

Endocrine System

Slow chemical communication via hormones in the bloodstream; the pituitary ('master gland') is controlled by the hypothalamus.

Circadian Rhythm

Roughly 24-hour biological clock regulated by the suprachiasmatic nucleus; light suppresses melatonin from the pineal gland.

REM Sleep

Rapid-eye-movement stage with vivid dreams, active brain, and paralyzed muscles ('paradoxical sleep'); REM rebound follows deprivation.