Neurobiology: Cellular Neurophysiology, Synaptic Transmission, and Psychopharmacology

Comprehensive vocabulary flashcards covering neurophysiology, resting potentials, action potential mechanics, neurotransmitter synthesis and pathways, receptor classes, and psychopharmacological mechanisms.

Resting Membrane Potential

The baseline electrical difference across a neuronal membrane when inactive, typically measuring $-65\,\text{mV}$, maintained by membrane impermeability and ion transport.

Concentration Gradient (Force of Diffusion)

The physical force driving ions to disperse from a region of higher concentration to a region of lower concentration.

Electrical Gradient (Electrostatic Pressure)

The electrical force that attracts ions toward regions of opposite charge and repels them away from regions of the same charge.

Depolarization

A shift in a neuron's membrane potential that makes the interior of the cell less negative (less different from the outside), typically driven by an influx of positive ions such as $Na^+$ or $Ca^{2+}$.

Hyperpolarization

A shift in a neuron's membrane potential that makes the interior of the cell more negative (more different from the outside), produced when positive ions like $K^+$ leave or negative ions like $Cl^-$ enter.

Sodium-Potassium ($Na^+/K^+$) Pump

A primary active transporter that maintains resting potential by expelling $3\,Na^+$ ions from the neuron for every $2\,K^+$ ions it imports.

Threshold of Excitation

The critical membrane voltage at the axon hillock, approximately $-40\,\text{mV}$, that triggers the opening of voltage-gated $Na^+$ channels to initiate an action potential.

"All-or-None" Property

The principle that an action potential fires completely or not at all, always regenerating to the same size and peak voltage (up to approximately $+40\,\text{mV}$).

Saltatory Conduction

The rapid propagation of action potentials along myelinated axons in which the electrical signal regenerates at and leaps between successive nodes of Ranvier.

Conduction Velocity Determinants

The two structural factors that govern the speed of an action potential: axon diameter (wider diameters conduct faster) and myelination (greater myelin insulation conducts faster).

Excitatory Postsynaptic Potential (EPSP)

A local, graded depolarization of the postsynaptic membrane caused by the influx of cations such as $Na^+$, $K^+$, or $Ca^{2+}$.

Inhibitory Postsynaptic Potential (IPSP)

A local, graded hyperpolarization of the postsynaptic membrane generated by the influx of $Cl^-$ or the efflux of $K^+$.

Spatial Summation

The integration of postsynaptic potentials (EPSPs and IPSPs) simultaneously triggered across distinct synaptic locations on a single postsynaptic neuron.

Temporal Summation

The integration of successive postsynaptic potentials generated at the exact same synapse in rapid succession over time.

Ionotropic Receptor

A ligand-gated channel protein that directly opens an integral ion pore upon neurotransmitter binding, yielding immediate, rapid, and short-lived ion flux.

Metabotropic Receptor

A membrane receptor coupled to an intracellular G-protein that initiates slower, longer-lasting intracellular signaling cascades and can induce changes in gene expression.

Basal Forebrain

The synthesis nucleus in the forebrain that produces acetylcholine for distribution to targets involved in learning, memory, attention, and arousal.

Substantia Nigra

The midbrain nucleus responsible for synthesizing dopamine, critical for motor control/movement, reward/motivation, and executive function.

Raphe Nuclei

The collection of nuclei spanning the medulla, pons, and midbrain that synthesize serotonin to regulate mood, sleep-wake cycles, and appetite.

Locus Coeruleus

The pontine nucleus that synthesizes norepinephrine, serving functions in arousal, vigilance, attention, and the fight-or-flight response.

Reuptake

A synaptic clearance mechanism where specialized transporter proteins in the presynaptic terminal or surrounding glial cells retrieve neurotransmitters (such as dopamine, serotonin, norepinephrine, GABA, or glutamate) from the synaptic cleft.

Enzymatic Degradation

The clearance of neurotransmitters from the synaptic cleft via chemical breakdown by specific enzymes, such as the degradation pathway used for acetylcholine.

Catecholamines

A family of monoamine neurotransmitters synthesized from phenylalanine, tyrosine, and L-DOPA that consists specifically of dopamine, norepinephrine, and epinephrine.

Monoamines

A classical group of biogenic amine neurotransmitters comprising the three catecholamines (dopamine, norepinephrine, epinephrine) along with serotonin.

Peptide Neurotransmitters

Neuropeptide chemical messengers—such as oxytocin, endorphins, substance P, and vasopressin—that commonly double as hormones circulating in the bloodstream.

Gas Neurotransmitters

Gaseous signaling molecules such as nitric oxide that cannot be packaged into synaptic vesicles because they freely diffuse through lipid bilayers, requiring on-demand synthesis.

Agonist

A substance that activates signaling by directly binding and activating a receptor, stimulating neurotransmitter release, or blocking reuptake transporters or degrading enzymes.

Antagonist

A substance that reduces signaling by binding to a receptor and blocking it, or by inhibiting neurotransmitter release.

Drug Tolerance

A state of decreased drug responsiveness resulting from repeated exposure, causing the dose-response curve to shift to the right and requiring higher doses to elicit the same effect.

Drug Sensitization

An enhancement in drug responsiveness produced by repeated exposure, shifting the dose-response curve to the left.

Therapeutic Index

The margin of safety separating a drug's effective therapeutic dose from its toxic or lethal dose; a narrow therapeutic index indicates a high risk of overdose.

Methadone

A long-acting opioid agonist that binds to heroin and morphine receptors to combat opioid addiction without producing an intense rush or crash.

Naloxone

An opioid receptor antagonist that reverses life-threatening opioid overdoses by outcompeting opioid agonists due to its higher binding affinity for the receptor.

Acamprosate

A pharmacological agent acting on NMDA receptors used to diminish withdrawal symptoms associated with alcohol dependence.

Naltrexone

An opioid antagonist utilized in treating alcohol use disorder by blunting the activation of the alcohol reward system.

Positive Symptoms

Psychopathological features characterized by the presence or addition of abnormal experiences (e.g., hallucinations), which are effectively reduced by first-generation antipsychotics that block $D_2$ receptors.

Negative Symptoms

Psychopathological features characterized by the absence or deficit of normal psychological functions (e.g., lack of pleasure, limited motivation), targeted preferentially by atypical antipsychotics that influence serotonin systems.

Mesolimbic Dopaminergic Pathway

The neural tract extending from the ventral tegmental area (VTA) to the nucleus accumbens that encodes reward, motivation, and reinforcement, naturally activated by eating food and social interaction.

Disinhibition (VTA Circuitry)

The process by which opioids increase dopamine neuron firing in the VTA by inhibiting local GABAergic interneurons, thereby eliminating their baseline inhibitory control.

Cocaine

A psychostimulant drug that augments synaptic dopamine levels in the nucleus accumbens by directly blocking the dopamine reuptake transporter.

Amphetamine

A psychostimulant that increases extracellular dopamine by acting on dopamine transporters to stimulate reverse transport and enhance neurotransmitter release.

MDMA (Ecstasy)

A psychoactive drug that enters serotonergic terminals via serotonin transporters to increase synaptic serotonin availability, while simultaneously raising dopamine, oxytocin, and vasopressin levels.

CB1 Receptor

The cannabinoid receptor stimulated by THC (endogenous ligand: anandamide), located predominantly within the hippocampus, cerebellum, and basal ganglia.

Moral Model of Addiction

A model of addiction positing that substance abuse is the consequence of individual personal choices and character deficits.

Disease Model of Addiction

A medical framework defining substance addiction as an identifiable, treatable physical disorder rather than a moral failure.