AP Psychology Unit 1 - Biological Basis of Behavior

Biological Psychology

The scientific study of the links between biological (genetic, neural, hormonal) and psychological processes.

Neuron

A nerve cell; the basic building block of the nervous system.

Presynaptic Neuron

The neuron that sends the signal across the synapse.

Postsynaptic Neuron

The neuron that receives the signal across the synapse.

Dendrites

Branchlike extensions of a neuron that receive messages and conduct impulses toward the cell body.

Dendritic Spines

Small protrusions on dendrites that increase surface area for synaptic connections.

Axon

The long extension of a neuron that carries impulses away from the cell body.

Axon Terminal

The endpoint of an axon where neurotransmitters are stored and released.

Vesicles

Small sacs in the axon terminal that contain neurotransmitters.

Myelin Sheath

Fatty tissue layer encasing axons; increases transmission speed of neural impulses.

Resting Potential

The neuron’s stable, negative charge when inactive (~ -70mV).

Action Potential

A brief electrical charge that travels down the axon when a neuron fires

Refractory Period

A brief time after an action potential during which a neuron cannot fire again

Threshold

The level of stimulation required to trigger a neural impulse.

All-or-None Response

A neuron either fires completely or not at all—no partial firing

Synapse

The junction between the axon tip of the sending neuron and the dendrite of the receiving neuron.

Adrenaline

A hormone and neurotransmitter involved in the fight-or-flight response; increases heart rate, blood flow, and energy. High levels can lead to anxiety and restlessness, while low levels may cause fatigue and poor stress response.

Noradrenaline

Helps control alertness and arousal; linked to stress response and mood regulation. Excess can cause elevated blood pressure and mania; deficiency is associated with depression and low energy.

Dopamine

Influences movement, learning, attention, and emotion; central to reward and pleasure systems. High levels are linked to schizophrenia and addictive behaviors, while low levels can result in Parkinson’s disease symptoms and depression.

Serotonin

Regulates mood, hunger, sleep, and arousal; promotes emotional stability. Too much may cause serotonin syndrome (rare), while too little is associated with depression, anxiety, and insomnia.

GABA

The brain’s primary inhibitory neurotransmitter; calms neural activity and prevents overstimulation. High levels can lead to sedation and impaired cognition; low levels are linked to anxiety, seizures, and sleep disturbances.

Acetylcholine

Enables muscle action, learning, and memory; essential for voluntary movement. Excess may cause muscle spasms, while deficiency is associated with Alzheimer’s disease and paralysis.

Glutamate

The brain’s main excitatory neurotransmitter; involved in memory and learning. High levels can trigger migraines and seizures, while low levels may impair cognitive function and energy.

Endorphins

Natural painkillers produced by the brain; reduce pain and boost pleasure. Elevated levels can cause euphoria and numbness to pain, while low levels may increase pain sensitivity and contribute to mood disorders.

Substance P

A neurotransmitter involved in the transmission of pain signals; high levels intensify pain perception.

Oxytocin

A hormone and neurotransmitter linked to bonding, trust, and social connection; elevated levels promote attachment and emotional closeness.

Excitatory

Describes neurotransmitters or signals that increase the likelihood of a neuron firing an action potential (e.g., glutamate)

Inhibitory

Describes neurotransmitters or signals that decrease the likelihood of a neuron firing (e.g., GABA)

Reuptake

The process by which neurotransmitters are reabsorbed by the presynaptic neuron after transmission; affects how long neurotransmitters influence the postsynaptic cell.

Agonist

A chemical or drug that mimics a neurotransmitter and activates its receptor (e.g., morphine mimics endorphins).

Antagonist

A chemical or drug that blocks a neurotransmitter’s receptor, preventing its action (e.g., naloxone blocks opioid receptors).

Nervous System

The body’s electrochemical communication network, consisting of all nerve cells in the central and peripheral systems.

Central Nervous System (CNS)

Composed of the brain and spinal cord; responsible for processing and decision-making.

Peripheral Nervous System (PNS)

All nerves outside the brain and spinal cord; connects the CNS to the rest of the body.

Somatic Nervous System

A subdivision of the PNS that controls voluntary movements of skeletal muscles.

Sympathetic Nervous System

A branch of the autonomic nervous system that activates the fight-or-flight response; increases heart rate, dilates pupils, and inhibits digestion.

Synaptic Gap/Cleft

The tiny space between the axon terminal of the sending neuron and the dendrite of the receiving neuron where neurotransmitters are released.

Parasympathetic Nervous System

A branch of the autonomic nervous system that calms the body after stress; slows heart rate and promotes digestion.

Spinal Reflex

An automatic response to a stimulus that occurs without brain involvement; processed by the spinal cord.

Endocrine System

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

Hormones

Chemical messengers produced by endocrine glands that travel through the bloodstream to affect other tissues.

Adrenal Glands

Endocrine glands above the kidneys that release adrenaline and noradrenaline during stress.

Pituitary Gland

The “master gland” of the endocrine system; regulates growth and controls other glands under the influence of the hypothalamus.

Lesion

Tissue destruction; used in neuroscience to study brain function by observing effects of damage

Electroencephalogram (EEG)

A recording of electrical activity in the brain using electrodes placed on the scalp; useful for studying sleep and seizures.

fMRI (Functional Magnetic Resonance Imaging)

A brain imaging technique that shows blood flow and brain activity by comparing successive MRI scans.

Brainstem

The oldest part of the brain; responsible for automatic survival functions like heartbeat and breathing.

Medulla

Located at the base of the brainstem; controls vital functions such as heartbeat and breathing.

Thalamus

The brain’s sensory relay station; directs messages to sensory receiving areas in the cortex (except smell).

Reticular Formation

A nerve network in the brainstem that plays a role in arousal and alertness.

Cerebellum

The “little brain” at the rear of the brainstem; coordinates voluntary movement and balance.

Limbic System

A neural system including the hippocampus, amygdala, and hypothalamus; associated with emotions and drives.

Amygdala

Two lima bean-sized neural clusters in the limbic system; linked to emotion, especially fear and aggression.

Hypothalamus

A neural structure below the thalamus; regulates hunger, thirst, body temperature, and controls the pituitary gland.

Cerebral Cortex

The brain’s outer layer of neural tissue; responsible for higher-order functions like thinking, planning, and decision-making.

Glial Cells

Support cells in the nervous system that nourish, protect, and insulate neurons.

Frontal Lobes

Located behind the forehead; involved in speaking, muscle movements, planning, and judgment.

Parietal Lobes

Located at the top of the head; processes sensory input for touch and body position.

Occipital Lobes

Located at the back of the head; responsible for visual processing.

Temporal Lobes

Located above the ears; involved in auditory processing and memory.

Eugenics

A controversial and unethical movement aimed at improving genetic quality through selective breeding; historically linked to discrimination and human rights abuses.

Myasthenia Gravis

A chronic autoimmune neuromuscular disorder that causes weakness in voluntary muscles due to impaired acetylcholine transmission.

Basal Ganglia

A group of structures deep in the brain that help coordinate voluntary movement and procedural learning; dysfunction is linked to Parkinson’s and Huntington’s disease.

Motor Cortex

Located in the rear of the frontal lobes; controls voluntary movements by sending signals to muscles.

Somatosensory Cortex

Located in the front of the parietal lobes; processes sensory input like touch, temperature, and pain.

Association Areas

Regions of the cerebral cortex not involved in primary motor or sensory functions; responsible for higher mental functions like learning, memory, and reasoning.

Plasticity

The brain’s ability to change and adapt, especially after injury or through learning; more pronounced in younger brains.

Neurogenesis

The formation of new neurons in the brain; occurs in limited regions like the hippocampus and can be stimulated by exercise and learning.

Corpus Callosum

A large band of neural fibers connecting the two brain hemispheres and allowing communication between them.

Split Brain

A condition resulting from surgery that severs the corpus callosum; reveals how each hemisphere processes information independently.

Behavior Genetics

The study of how genetic and environmental factors influence behavior

Nature vs. Nurture

A longstanding debate over the relative contributions of genetics (nature) and environment (nurture) to psychological traits.

Twin Studies

Research comparing identical and fraternal twins to assess genetic influence on traits and behaviors

Epigenetics

The study of how environmental factors can influence gene expression without changing DNA; explains how nurture can affect nature

Phrenology

A discredited theory that claimed bumps on the skull could reveal mental abilities and personality traits.

Contralateral Hemispheric Organization

The concept that each hemisphere of the brain controls the opposite side of the body (e.g., left brain controls right hand).

Broca’s Area

A region in the left frontal lobe responsible for speech production; damage causes difficulty speaking (Broca’s aphasia).

Wernicke’s Area

A region in the left temporal lobe involved in language comprehension; damage leads to fluent but nonsensical speech (Wernicke’s aphasia).