BioPsych Exam 1

Resting Potential

The baseline electrical charge of an inactive neuron's membrane, typically around $-70\,\text{mV}$ (ranging between $-40\,\text{mV}$ and $-80\,\text{mV}$), maintained by closed voltage-gated channels and active sodium-potassium pumps.

Threshold

The critical membrane potential voltage level, typically around $-55\,\text{mV}$, required to open voltage-gated sodium channels and trigger an action potential.

Local Potential (Graded Potential)

A small depolarization on the neuronal membrane that varies in magnitude according to stimulus intensity and decreases in strength over distance and time without reaching threshold.

Ungraded

A characteristic of action potentials indicating that once threshold is reached, the neuron fires at a uniform, fixed intensity regardless of the strength of the initiating stimulus.

Nondecremental

A property of action potentials specifying that the signal maintains a constant magnitude as it propagates down the entire length of the axon.

Decremental

A property of graded signals meaning that the electrical disturbance gradually diminishes in magnitude over distance and time.

All-or-None Law

The principle that an action potential is either generated completely at full intensity once threshold is met or fails to fire entirely if threshold is not reached.

Axon Hillock

The specialized region at the junction of the soma and axon where incoming signals are integrated and the initial spike is generated.

Depolarization

The initial phase of an action potential during which voltage-gated $\text{Na}^+$ channels open, allowing sodium ions to rush into the cell and shifting the membrane potential from negative to positive (approximately $+30\,\text{mV}$ to $+40\,\text{mV}$).

Repolarization

The resetting phase of an action potential in which sodium channels close and potassium channels open, allowing $\text{K}^+$ ions to exit the cell and restoring a negative internal membrane charge.

Hyperpolarization

A temporary phase following the restoration of baseline potential where the membrane becomes more negative than rest (around $-80\,\text{mV}$) due to lingering open potassium channels.

Absolute Refractory Period

The brief duration during depolarization and repolarization when sodium channels are inactivated, rendering the neuron completely incapable of firing another spike regardless of stimulus strength.

Relative Refractory Period

The duration during hyperpolarization when a neuron can fire a second signal, but requires a stronger-than-normal excitatory stimulus to reach threshold.

Nodes of Ranvier

Small, unmyelinated gaps of approximately $1\,\text{mm}$ along a wrapped axon where voltage-gated ion channels are concentrated to rapidly regenerate signal intensity.

Sodium-Potassium Pumps

Active transport mechanisms in the neural membrane that maintain baseline voltage by expelling $3\,\text{Na}^+$ ions out of the cell for every $2\,\text{K}^+$ ions brought in.

Ion Channels

Protein pores spanning the lipid bilayer that selectively regulate the flow of specific charged particles across the neuronal membrane.

Ligand

A chemical molecule (such as a neurotransmitter) that specifically binds to a receptor to open/close gated pores.

Voltage

The potential difference in electrical charge between two points, such as the inside and outside of a neuronal membrane.

Polarization

The existence of a difference in electrical charge across a cell membrane, characterized by an excess of negative ions inside relative to the outside.

Diffusion

The passive movement of molecules or ions from an area of higher concentration to an area of lower concentration down their gradient.

Electrostatic Pressure

The electrical force causing like-charged ions to repel each other and oppositely charged ions to attract each other.

Neural Membrane

A semi-permeable lipid bilayer containing embedded protein channels and pumps that encloses the cell and regulates ionic environments.

Anions ($\text{A}^-$)

Large, negatively charged protein molecules located inside the intracellular fluid that cannot cross the lipid boundary.

Biopsychology

The scientific branch of psychology that investigates the physiological, neural, and genetic bases of behavior and mental processes.

Behavior

All observable actions and internal states of an organism, encompassing overt actions, speech, thoughts, and emotional responses.

Dualism

The philosophical view asserting that the mind (or soul) and the physical body are two distinct, non-identical entities.

Monism

The philosophical perspective asserting that the mind and body are components of a single, unified reality or physical substance.

Idealistic Monism

A philosophical position holding that all existing reality consists exclusively of non-physical mind or mental phenomena.

Materialistic Monism

A philosophical position proposing that everything in existence is physical matter, meaning mental processes are entirely products of physical brain activity.

Trephining

An ancient surgical technique dating back to $5000\,\text{BCE}$ in which holes were drilled into a patient's skull.

Ebers and Edwin Smith Papyrus

Ancient Egyptian medical texts dating to $1550\,\text{BCE}$ (with origins up to $1500$ years earlier) containing $48$ clinical case reports detailing brain anatomy and injuries while attributing the soul to the heart.

Hydraulic Theory of Human Behavior

René Descartes's early 17th-century model proposing that human movement is produced by pressurized fluids flowing through hollow nerves.

Luigi Galvani

An 18th-century researcher who demonstrated that electrical stimulation of frog leg nerves produced muscle contractions, establishing that nerve conduction is electrical in nature.

Gustav Fritsch and Eduard Hitzig

19th-century researchers who applied electrical stimulation to dog cerebral cortexes in $1870$, demonstrating localized motor control in the brain.

Hermann von Helmholtz

A 19th-century scientist who measured the speed of nerve conduction, proving neural transmission is an electrochemical process rather than pure electricity.

Localization of Function

The principle that distinct brain regions are specialized to control specific behaviors, cognitive operations, or sensory processes.

Phrenology

A pseudoscientific 19th-century theory developed by Franz Gall and J.G. Spurzheim claiming that personal traits and faculties could be determined by measuring bumps on the human skull.

Broca's Area

A region in the left frontal lobe identified in $1861$ as essential for motor speech production.

Equipotentiality

Karl Lashley's early 20th-century hypothesis proposing that all parts of the cerebral cortex contribute equally to complex cognitive functions like learning and memory.

Distributed Function

The modern consensus model showing that complex psychological functions rely on integrated neural networks spanning multiple brain regions, evidenced by studies with Patient H.M., Brenda Milner, and Mortimer Mishkin.

Tabula Rasa

John Locke's 17th-century concept describing the human mind at birth as a blank slate shaped entirely by sensory experiences and environmental input.

Sir Francis Galton

A 19th-century scientist who coined and popularized the phrase 'Nature vs. Nurture' to debate the relative contributions of heredity and environment.

Natural Selection

Charles Darwin's evolutionary mechanism wherein organisms possessing traits better suited to environmental pressures are more likely to survive and pass those heritable traits to offspring.

Strategic Pluralism

An evolutionary psychology concept proposing that multiple, distinct behavioral strategies can co-exist within a population due to environmental trade-offs.

Evolution of Skin Tone

An adaptive trait driven by solar UV radiation levels: high UV equatorial regions selected for darker pigmentation to protect against folate breakdown, while low UV high-latitude regions selected for lighter pigmentation to allow sufficient UV absorption for Vitamin D synthesis.

Adaptive Emotion

The perspective that emotional states evolved as functional behavioral adaptations that increase survival and reproductive fitness.

Watson and Crick Model of DNA

The $1953$ structural model proposing that genetic material is organized as a double helix composed of nucleotide chains.

Nucleotides

The fundamental building blocks of DNA, consisting of a sugar, phosphate group, and nitrogenous base pair (Adenine with Thymine, and Cytosine with Guanine).

Chromosomes

Structures made of tightly coiled DNA containing genes, organized into $23$ pairs in human cells ($22$ autosome pairs and $1$ pair of sex chromosomes, X and Y).

Alleles

Alternative molecular variations or sequences of a specific gene.

Homozygous

Possessing two identical variations of a given gene on homologous chromosomes.

Heterozygous

Possessing two different variations of a given gene on homologous chromosomes.

Genotype

The specific genetic makeup or complete set of inherited alleles of an organism.

Phenotype

The observable physical, physiological, or behavioral traits produced by the interaction of inherited genes with the environment.

Monogenic Effect

A pattern of genetic inheritance in which a single gene determines the expression of a specific trait.

Polygenic Effect

A pattern of genetic inheritance in which a trait is influenced by the combined additive effects of multiple genes.

Gene Expression

The biological mechanism through which genetic information encoded in DNA is transcribed and translated to produce functional proteins, effectively turning traits on or off.

Epigenetics

The study of heritable changes in gene activity or cellular phenotype caused by environmental influences without altering the underlying DNA sequence.

X-Linked Recessive Traits

Conditions caused by recessive alleles carried on the X chromosome, such as red-green color blindness, hemophilia A, and male-pattern baldness, which express more frequently in males.

X-Linked Dominant Traits

Conditions caused by dominant alleles on the X chromosome, such as Rett syndrome and Vitamin D resistant rickets, which express with a single copy in both males and females.

Twin Studies

Research designs comparing identical (monozygotic) pairs sharing $100\%$ of their genes with fraternal (dizygotic) pairs sharing approximately $50\%$ of their genes to estimate heritability versus environmental influence.

Central Nervous System (CNS)

The primary structural division of the nervous system consisting of the brain and the spinal cord.

Peripheral Nervous System (PNS)

The structural division of the nervous system comprising all neural tissue located outside the brain and spinal cord.

Motor Neurons

Efferent multipolar cells that convey neural signals away from the Central Nervous System to muscles and glands.

Sensory Neurons

Afferent unipolar or bipolar cells that transmit information from receptors toward the Central Nervous System.

Interneuron

Multipolar cells located entirely within the Central Nervous System that process local reflex pathways and connect input and output pathways.

Afferent

Neural pathways or messages moving inward toward the Central Nervous System.

Efferent

Neural pathways or messages moving outward away from the Central Nervous System toward effector organs.

Myelin Sheath

A fatty insulating layer surrounding many axons that increases the conduction velocity of action potentials.

Dendrites

Branching neuronal extensions that receive inputs and chemical signals from neighboring cells and conduct graded potentials toward the cell body.