Biological Bases of Behavior and Sensation & Perception

Comprehensive practice flashcards covering biological bases of behavior, genetics, neuroanatomy, neurotransmission, sleep, and sensation and perception.

Twin studies

Research that compares identical and fraternal twins to determine the influence of genetics and environment on human traits, behaviors, and conditions; identical twins share $100\%$ of their genes, whereas non-identical twins share $50\%$.

Family studies

A key research tool in behavioral genetics that assesses how similar biological family members are in their physical, psychological, and behavioral characteristics to determine the relative contribution of genes and environment.

Adoption studies

Research studies that compare the behavior of adopted children to their biological and adoptive parents to evaluate the influence of genetics and environment, noting that adoptive parents typically share $0\%$ of genes with adopted children.

Psychology

The scientific study of mind and behavior, covering conscious and unconscious phenomena, mental processes like thoughts, feelings, and motives, as well as how biology influences thought and behavior.

Nature-nurture issue

The question of how much an individual's characteristics are formed by innate biological factors such as genetics ("nature") versus upbringing and life experiences ("nurture").

Heredity

The transmission of traits, characteristics, and predispositions from parents to offspring through genetic material (chromosomes, DNA, and genes) and the study of how genetic factors contribute to individual differences.

Natural selection

An evolutionary mechanism stating that organisms better suited to their environment are more likely to survive and reproduce, passing on their genes to subsequent generations and causing species to adapt over time.

Reproductive success

The ability of an individual to produce offspring that can pass on their genes to the next generation; a central component of evolutionary fitness.

Eugenics

A pseudoscientific movement that promoted the idea that the human population could be improved through selective breeding and genetics by allowing only certain individuals to reproduce.

Chromosomes

Thread-like structures located within the nucleus of a cell, composed of DNA and proteins, which carry genetic packages of genes passed from parents to offspring.

DNA

The molecule within cells that carries genetic information, serving as the blueprint for an organism's development, physical functions, and behavioral and psychological traits.

Genes

Segments of DNA that act as the fundamental units of heredity; they code for proteins that determine bodily structure and both physical and psychological characteristics.

Central nervous system (CNS)

The division of the nervous system composed of the brain and spinal cord that acts as the body's primary processing center, receiving sensory input, integrating it, and directing motor commands.

Peripheral nervous system (PNS)

The network of nerves branching outward from the brain and spinal cord that connects the central nervous system to organs, muscles, and sensory structures throughout the body.

Autonomic nervous system

The branch of the nervous system responsible for regulating involuntary bodily functions—such as heart rate, respiration, and digestion—without conscious control; subdivided into sympathetic and parasympathetic branches.

Somatic nervous system

The division of the peripheral nervous system that governs voluntary muscle contractions and relays sensory information from the body back to the central nervous system.

Parasympathetic nervous system

The "rest and digest" branch of the autonomic nervous system that conserves energy, promotes digestion and salivation, and restores the body to a calm physiological state after stress.

Sympathetic nervous system

The branch of the autonomic nervous system that mobilizes the body's "fight, flight, or freeze" response by elevating heart rate, dilating pupils, and redirecting energy to prepare for acute action.

Spinal cord

A central nervous system structure connecting the brain to the rest of the body that acts as a sensory-motor relay station, contains central pattern generators, and coordinates automatic spinal reflexes.

Glial cells

Non-neuronal cells in the nervous system that support, nourish, and protect neurons, form myelin sheaths, maintain chemical homeostasis, and aid in brain repair without generating electrical impulses.

Reflex arc

A complete neural pathway that produces an automatic, involuntary motor response to a sensory stimulus without requiring brain processing, comprising a receptor, sensory neuron, interneuron, motor neuron, and effector.

Sensory neuron (afferent neuron)

A specialized nerve cell that detects sensory input from receptor organs and transmits this information as electrical signals to the central nervous system.

Motor neuron (efferent neuron)

A nerve cell located in the brain or spinal cord that transmits instructional motor signals from the central nervous system to effector muscles to cause movement.

Interneuron

A central nervous system neuron (also called an association neuron) that connects sensory and motor pathways and participates in complex cognitive functions including memory and learning.

All-or-none principle of neural firing

The principle that a neuron fires an action potential at full strength if stimulation surpasses threshold, or it does not fire at all; stimulus intensity does not alter impulse magnitude.

Resting potential

The stable electrical membrane charge maintained by a neuron when it is inactive and not transmitting a nerve impulse, typically measured around $-70\text{ mV}$.

Depolarization

The process by which the interior of a neuron becomes less negative due to an influx of positive ions across the membrane, initiating an action potential once threshold is reached.

Refractory period

The brief recovery phase following the generation of a response or action potential during which a neuron, muscle, or organ cannot immediately fire another response.

Reuptake

The reabsorption of excess neurotransmitter molecules from the synaptic cleft back into the presynaptic neuron that released them.

Threshold for neural firing

The minimum membrane potential level of stimulation—typically around $-55\text{ mV}$\—required to trigger an action potential in a neuron.

Multiple sclerosis

An immune-mediated disorder wherein the body's immune system attacks and damages the myelin sheath insulating central nervous system neurons, degrading nerve signal propagation.

Myasthenia gravis

An autoimmune disorder characterized by antibodies attacking acetylcholine receptors (AChR) on muscle fibers, interrupting neuromuscular communication and inducing muscle weakness.

Dopamine

A neurotransmitter that functions in the brain's reward and pleasure pathways, voluntary movement, and decision-making; implicated in Parkinson's disease when deficient and schizophrenia when excessive.

Serotonin

An inhibitory neurotransmitter synthesized from tryptophan (mostly found in the gut) that modulates mood, behavior, sleep, and memory; low levels are linked to depression.

Norepinephrine

A neurotransmitter and hormone (noradrenaline) that stimulates the "fight, flight, or freeze" response by increasing alertness, elevating heart rate, and constricting blood vessels during stress.

Glutamate

The primary and most abundant excitatory neurotransmitter in the brain and central nervous system, playing a critical role in cognitive processes, learning, and memory formation.

GABA

The principal inhibitory neurotransmitter in the central nervous system that reduces neural hyperactivity to promote calmness; absence can cause tremors, convulsions, and seizures.

Endorphins

Endogenous opioid neuropeptides and hormones that act as natural painkillers by inhibiting pain signal transmission in the nervous system, elevating mood, and generating euphoric sensations.

Substance P

An excitatory neurotransmitter and neuromodulator involved in transmitting pain information to the central nervous system, elevating pain sensitivity, and mediating inflammatory processes.

Acetylcholine

An excitatory neurotransmitter active at neuromuscular junctions that triggers muscle contractions and plays critical roles in learning, short-term memory, and attention.

Hormones

Chemical messengers secreted directly into the bloodstream by endocrine glands that travel systemically to influence physiology, mood, aggression, growth, and reproduction.

Leptin

A hormone produced by adipose (fat) tissue that signals satiety to the hypothalamus to suppress appetite and maintain long-term energy balance.

Ghrelin

The stomach-produced "hunger hormone" that travels through the bloodstream to the brain to stimulate appetite and signal the need to consume food.

Melatonin

A neurohormone synthesized by the pineal gland during darkness that synchronizes the sleep-wake cycle and circadian rhythms.

Oxytocin

A hormone often called the "love hormone" or "cuddle chemical" that fosters pair bonding, trust, empathy, social reward, and reduction of stress and anxiety.

Agonist

A chemical or pharmacological agent that binds to a neurotransmitter receptor site and mimics or amplifies the biological action of that neurotransmitter.

Antagonist

A chemical substance that binds to a receptor site and blocks or dampens the normal physiological response elicited by a neurotransmitter.

Reuptake inhibitor

A class of drugs (such as SSRIs and SNRIs) that prevent the presynaptic reabsorption of neurotransmitters, increasing their concentration and persistence in the synaptic cleft.

Stimulants

A class of psychoactive drugs (e.g., caffeine, cocaine, amphetamines) that accelerate central nervous system activity, boosting energy, arousal, alertness, and cardiovascular output.

Depressants

Substances (such as alcohol) that decrease central nervous system arousal, slowing neural processing, coordination, and bodily reflexes while diminishing inhibition.

Opioids

A category of natural and synthetic analgesic compounds derived from or modeled after the opium poppy that alleviate pain and produce euphoria, carrying substantial risks of addiction.

Medulla

A lower brainstem structure situated at the base of the skull that regulates essential involuntary survival reflexes, including respiration, heart rate, blood pressure, and vomiting.

Reticular activity system (reticular formation)

A neural network residing in the brainstem that filters extraneous sensory information and regulates states of consciousness, wakefulness, and general cortical arousal.

Cerebellum

A hindbrain structure located beneath the cerebrum responsible for voluntary movement precision, balance, posture maintenance, and procedural motor learning.

Limbic system

An interconnected cluster of subcortical brain structures (including the amygdala, hippocampus, hypothalamus, and thalamus) dedicated to emotion processing, memory consolidation, and motivation.

Thalamus

The subcortical sensory routing hub that directs incoming sensory impulses from all modalities (except olfaction) to corresponding primary sensory regions of the cerebral cortex.

Hypothalamus

A limbic structure below the thalamus that maintains internal homeostasis by directing the autonomic nervous system and governing fundamental biological drives like hunger, thirst, sex, and temperature.

Hippocampus

A limbic structure critical for memory consolidation—converting temporary short-term memories into enduring long-term storage—and spatial cognition.

Amygdala

A limbic structure primarily responsible for detecting environmental threats and orchestrating emotional processing, specifically fearful and aggressive responses.

Corpus callosum

The broad, dense band of neural axon fibers connecting the cerebral hemispheres, permitting continuous interhemispheric communication.

Frontal lobes

The anterior lobes of the cerebral cortex responsible for motor control via the motor cortex, expressive speech via Broca's area, impulse regulation, and executive cognitive functioning.

Prefrontal cortex

The anterior-most portion of the frontal lobe that acts as the brain's executive control center, directing working memory, top-down inhibition, planning, and personality expression.

Parietal lobes

Cerebral lobes positioned at the superior rear of the brain containing the somatosensory cortex, which processes sensations of touch, pressure, temperature, and body positioning.

Occipital lobes

The posterior cortical lobes of the brain dedicated primarily to processing visual information received from the eyes.

Temporal lobes

The lateral cortical lobes situated along the sides of the brain, containing primary auditory processing regions and Wernicke's area for speech comprehension.

Broca's area

A region situated in the left frontal lobe that directs speech articulation and motor language production; damage induces expressive aphasia.

Wernicke's area

A region in the left temporal lobe essential for comprehending spoken and written language; damage results in receptive aphasia where speech remains fluent but meaningless.

Brain plasticity (neuroplasticity)

The nervous system's capacity to structurally and functionally reorganize its neural pathways and connections throughout life in response to learning, experience, or neurological injury.

Neurogenesis

The biological generation and integration of new neurons in the brain, predominantly observed throughout life in specialized regions such as the hippocampus.

Circadian rhythm

An endogenous biological cycle spanning approximately $24\text{ hours}$ that synchronizes sleep-wake patterns, temperature variations, and endocrine release with environmental light-dark changes.

NREM 3

The deepest slow-wave stage of non-rapid eye movement sleep, distinguished by high-amplitude delta brain waves, physical restoration, and high arousal thresholds.

REM (rapid eye movement)

A sleep stage marked by rapid saccadic eye movements, wake-like cortical electrical patterns, vivid narrative dreaming, and complete skeletal muscle atonia (paradoxical sleep).

Activation-synthesis theory

A neurobiological dream hypothesis proposing that dreams represent the cerebral cortex's synthetic interpretation of random neural discharges originating in the brainstem during REM sleep.

Transduction

The conversion of ambient environmental physical energy (such as photons or pressure waves) into neurological electrochemical signals by specialized sensory receptors.

Absolute threshold

The minimum stimulus intensity required for sensory receptors and the brain to detect a sensory input at least $50\%$ of the time.

Difference threshold (just noticeable difference)

The smallest perceptible variation between two physical stimuli required for an observer to distinguish them at least $50\%$ of the time.

Weber's law

The psychophysical principle asserting that the difference threshold is a constant proportion or ratio of the initial stimulus magnitude, rather than a fixed quantitative value.

Sensory adaptation

The progressive reduction in sensory receptor firing rate and neural sensitivity that occurs when exposed to a continuous, unchanging physical stimulus.

Rods

Photoreceptors situated primarily in the retinal periphery that exhibit high light sensitivity, process black, white, and shades of gray, and detect peripheral motion under scotopic conditions.

Cones

Retinal photoreceptors densely packed within the central fovea that provide high visual acuity and mediate color discrimination across red, green, and blue wavelengths in bright light.

Opponent process theory

A visual theory positing that color perception relies on antagonistic ganglion cell channels arranged in three opposing pairs: red-green, blue-yellow, and black-white, accounting for color afterimages.

Place theory

An auditory pitch theory proposing that individual sound wave frequencies displace distinct physical regions along the cochlear basilar membrane, with higher pitches stimulating the base.

Volley theory

An auditory principle stating that intermediate pitch frequencies ($500\text{ - }5000\text{ Hz}$) are encoded by clusters of auditory neurons firing in staggered, rapid succession.

Gate control theory

A pain perception model stating that non-painful sensory input can close neural gates in the spinal cord's substantia gelatinosa, inhibiting pain signals from traveling onward to the brain.

Vestibular sense

The sensory system regulated by the fluid-filled semicircular canals and otolith organs of the inner ear that detects head orientation, movement through space, and balance.

Kinesthetic sense

The somatosensory system relying on proprioceptors embedded within muscles, tendons, and joints that detects limb positioning, bodily motion, and mechanical effort without visual guidance.