NPLEX I key terms

The body's active maintenance of stable internal conditions, such as temperature, pH, and blood glucose, through continuous feedback adjustments despite changes in the external environment.

A control mechanism in which the output of a process suppresses or reverses the stimulus that produced it, restoring a variable toward its set point. Most endocrine and autonomic regulation works this way.

A control mechanism in which the output of a process amplifies the original stimulus, driving a rapid change to completion rather than stability. Examples include childbirth contractions and blood clotting.

A rapid, all-or-none reversal of membrane voltage that travels along an excitable cell. Sodium channels open to depolarize, then potassium channels open to repolarize the membrane.

The steady electrical charge difference across a neuron's membrane at rest, typically about minus seventy millivolts, created mainly by potassium leak and the sodium-potassium pump.

An energy-consuming membrane protein that moves three sodium ions out and two potassium ions in per cycle, maintaining the ion gradients that underlie resting potential and secondary active transport.

A brief interval after an action potential during which the neuron cannot fire again (absolute) or requires a stronger stimulus to fire (relative), limiting firing frequency and direction of impulse travel.

The regulation of water and solute balance across body compartments, primarily through renal handling of sodium and water and through antidiuretic hormone and thirst mechanisms.

The volume of plasma filtered by the kidney glomeruli per unit time, a key index of renal function influenced by filtration pressure, surface area, and permeability.

A hormonal cascade triggered by low renal perfusion or low sodium that produces angiotensin II and aldosterone, raising blood pressure and promoting sodium and water retention.

The regulation of hydrogen ion concentration in body fluids, achieved by chemical buffers, respiratory control of carbon dioxide, and renal control of bicarbonate excretion and reabsorption.

The principal extracellular buffer, in which carbon dioxide and water equilibrate with carbonic acid and bicarbonate, allowing hydrogen ion changes to be moderated and exhaled as carbon dioxide.

A calculated difference between measured cations and anions (sodium minus chloride plus bicarbonate) used to classify metabolic acidosis and detect unmeasured acids such as ketones or lactate.

The cytoplasmic pathway that splits glucose into pyruvate, generating a small net yield of ATP and reducing equivalents, and which can proceed with or without oxygen.

A mitochondrial series of reactions that oxidizes acetyl coenzyme A derived from carbohydrates, fats, and proteins, producing reducing equivalents and carbon dioxide for later energy extraction.

The mitochondrial process in which electrons passed along a chain of carriers drive proton pumping and ATP synthesis, accounting for most cellular energy production and consuming oxygen.

The body's immediate, non-specific defense system including barriers, phagocytes, complement, and inflammation, which responds rapidly to threats without memory for specific pathogens.

A slower, antigen-specific defense system mediated by lymphocytes that develops memory, allowing faster and stronger responses upon re-exposure to the same pathogen.

A Y-shaped protein produced by plasma cells that binds a specific antigen, neutralizing pathogens or marking them for destruction by complement and immune cells.

A localized vascular and cellular response to injury or infection, classically marked by redness, heat, swelling, pain, and possible loss of function, aimed at removing the cause and repairing tissue.

The study of what the body does to a drug, encompassing absorption, distribution, metabolism, and elimination, which together determine the time course of drug concentration at its site of action.

The fraction of an administered drug dose that reaches systemic circulation unchanged, which is complete for intravenous dosing but often reduced for oral dosing.

Presystemic breakdown of an oral drug in the intestinal wall or liver before it reaches general circulation, reducing bioavailability and sometimes producing active or toxic metabolites.

The time required for the plasma concentration of a drug to fall by half, reflecting clearance and volume of distribution and guiding dosing intervals and time to steady state.

A ratio comparing a drug's toxic or lethal dose to its effective dose; a low index means small differences between therapeutic and harmful concentrations, requiring careful monitoring.

In diagnostic testing, the proportion of people who truly have a condition and are correctly identified as positive; a highly sensitive test is useful for ruling out disease when negative.

In diagnostic testing, the proportion of people without a condition who are correctly identified as negative; a highly specific test is useful for confirming disease when positive.

The probability that a person with a positive test result actually has the condition, which rises as disease prevalence in the tested population increases.

A reasoned list of possible conditions that could explain a patient's presentation, ranked and then narrowed through history, examination, and targeted testing before a working diagnosis is chosen.

A symptom, sign, or historical feature suggesting serious or urgent disease that warrants prompt investigation or referral rather than routine conservative management.

Standard physiological measurements, typically temperature, pulse, respiratory rate, blood pressure, and oxygen saturation, used to detect instability and track a patient's clinical course.

A life-threatening state of inadequate tissue perfusion that deprives cells of oxygen and nutrients, producing organ dysfunction; types include hypovolemic, cardiogenic, distributive, and obstructive.

A clinical circumstance in which a treatment or procedure should be withheld or altered because the risk of harm outweighs the expected benefit for that patient.

A harmful or unintended response to a medication given at appropriate doses, ranging from predictable dose-related effects to idiosyncratic reactions and interactions with other agents.

Systematically developed recommendations intended to guide practitioner and patient decisions about appropriate care for specific clinical circumstances, usually graded by strength of supporting evidence.

The integration of the best available research evidence with clinical expertise and patient values and preferences when making decisions about individual patient care.

A patient's voluntary agreement to a proposed treatment after receiving and understanding information about its nature, benefits, risks, and reasonable alternatives, including the option of refusal.

The range of duties, procedures, and responsibilities a licensed practitioner is legally and professionally permitted to perform based on training, licensure, and jurisdictional rules.