Lecture 1.2: The Scientific Method & Principles of Homeostasis

Vocabulary flashcards covering core terms and principles of homeostasis, feedback mechanisms, physiological limits, steady-state vs. equilibrium, and the scientific method.

Homeostasis

The condition in which the body's internal environment remains relatively constant within physiological limits.

Claude Bernard

Famous French physiologist (1813–1878) who stated that the constancy of the internal environment is the condition for a free and independent life ("La fixité du milieu intérieur est la condition d'une vie libre et indépendante").

La Leton de Claude Bernard (The Lesson of Claude Bernard)

An 1899 painting by French Naturalist painter and printmaker Léon-Augustin L'hermitte (1844–1925) depicting Claude Bernard demonstrating an experiment in his laboratory.

Physiological Parameters

Measurable physical and chemical characteristics of an organism (e.g., temperature, pH, concentrations of important molecules) that tend to remain constant over time.

Hypothesis

A tentative answer to a question derived from observations, which can be tested experimentally (distinct from the question itself).

Controlled Condition

A physical or chemical parameter of the internal environment (such as body temperature, blood sugar, or blood pressure) that is monitored and maintained near a stable mean.

Set Point

The stable mean value around which a controlled condition varies within the internal environment.

Physiological Limits

The threshold range of environmental and physical conditions (such as heat, moisture, pressure, and chemical composition) required to maintain the body's viability and keep it alive.

Negative Feedback Loop

A control mechanism that reverses or negates the original stimulus to maintain homeostasis, commonly used for conditions needing frequent adjustment like body temperature, blood sugar levels, and blood pressure.

Positive Feedback Loop

A control mechanism that intensifies or reinforces the original stimulus, seen during processes like normal childbirth (cervical stretch and oxytocin release).

Receptor

A feedback loop component (e.g., temperature sensor or stretch receptor) that monitors changes in a controlled condition and sends input signals.

Control Center

A feedback loop component (e.g., the brain) that evaluates input from receptors and determines the required output signals.

Effector

A feedback loop component (e.g., a sweat gland or uterine muscle) that receives output from the control center and produces a response that alters the controlled condition.

Steady-State

A constant state maintained over time that requires continuous energy expenditure (energetically expensive), maintaining living systems far away from equilibrium.

Equilibrium

A constant state achieved naturally without any energy expenditure; a special case of steady-state.

Core Body Temperature Set Point

The stable core temperature maintained by homeostasis in humans, sitting around $37.0^\text{o}\text{C}$ ($98.6^\text{o}\text{F}$) even when exposed to external temperatures like $20.0^\text{o}\text{C}$ ($68.0^\text{o}\text{F}$).