Key Medical Terminology

Common Word Roots in Anatomy & Physiology

Understanding medical terminology is essential for studying anatomy and physiology. Many terms are built from word roots that describe location, condition, or function.

Body Fluid Compartments

Organization of Body Fluids

The human body contains water distributed in distinct compartments, separated by epithelial and semipermeable membranes. Understanding these compartments is fundamental to physiology and the study of homeostasis.

• Total Body Water (TBW): The sum of all water in the body.

• Intracellular Fluid (ICF): Fluid contained within cells; typically about two-thirds of TBW.

• Extracellular Fluid (ECF): Fluid outside cells; about one-third of TBW.

• Transport: Movement of substances between compartments occurs across semipermeable membranes.

Example: In a 70 kg male:

• Total Body Water (TBW):

• Intracellular Fluid (ICF): (2/3 of TBW)

• Extracellular Fluid (ECF): (1/3 of TBW)

Subdivisions of Extracellular Fluid

The ECF is further divided into plasma and interstitial fluid (ISF), each with distinct roles in maintaining the internal environment.

• Plasma: The liquid component of blood; about 7% of TBW ().

• Interstitial Fluid (ISF): Fluid between cells; about 26% of TBW ().

Example: Plasma is the medium for transporting nutrients, hormones, and waste products in the blood.

Homeostasis

Central Principle of Physiology

Homeostasis is the process by which the body maintains a relatively constant internal environment, despite changes in the external environment. This dynamic constancy is essential for proper function and survival.

• Definition: Regulation of the body's internal environment to maintain stable conditions.

• Examples of regulated variables: Blood pressure, blood glucose, body temperature, fluid volume, and composition.

• Set Point: The expected value or steady state for a regulated variable (e.g., body temperature ).

Example: Blood glucose levels fluctuate throughout the day but are regulated to remain within a narrow range.

Homeostatic Control Systems

Homeostatic regulation involves several components that detect changes and initiate responses to restore balance.

• Receptors: Sensors that detect changes (stimuli) in the regulated variable; e.g., thermoreceptors, chemoreceptors.

• Integrating Centers: Usually regions of the brain that process information and orchestrate responses.

• Effectors: Muscles or glands that carry out the response to restore homeostasis.

• Signals: Communication pathways (nervous or chemical) between components.

Example: Thermoreceptors in the skin detect changes in temperature and send signals to the hypothalamus (integrating center), which then activates sweat glands (effectors).

Negative Feedback Control

Negative feedback is the primary mechanism for maintaining homeostasis. It works by detecting deviations from the set point and initiating responses that restore the variable to its normal range.

• Error Signal: The difference between the measured value and the set point.

• Negative Feedback: The response opposes the initial change, restoring the variable to the set point.

• Positive Feedback: The response amplifies the initial change (less common in physiology).

• Feed-forward Regulation: Anticipatory adjustments before a change occurs.

Example: Regulation of body temperature:

• Set point:

• If body temperature rises, mechanisms such as sweating and vasodilation are activated to cool the body.

• If body temperature falls, shivering and vasoconstriction help raise temperature.

Thermoregulation and Heat-Related Illness

Maintaining body temperature is a critical aspect of homeostasis. Extreme deviations can lead to serious health consequences.

• Normal body temperature: ()

• Hypothermia: Abnormally low body temperature.

• Hyperthermia: Abnormally high body temperature.

• Critical temperature: (fatigue), above (dangerous), above (deadly, heat stroke).

Heat Exhaustion vs. Heat Stroke:

• Heat exhaustion: Profuse sweating, skin flushed, blood flow to skin increases, reduced blood volume and pressure, dizziness, fainting.

• Heat stroke: No sweating, skin dry, temperature continues to climb, positive feedback loop, delirium, can be fatal.

Example: During heat stroke, the body's normal cooling mechanisms fail, leading to dangerous increases in body temperature.

Summary Table: Components of Homeostatic Control

Additional info: The notes infer standard values for fluid compartments and homeostatic set points based on typical physiology textbooks. The mechanisms of negative feedback and thermoregulation are expanded for clarity and completeness.