Anatomy & Physiology I - Homeostasis Quiz

Anatomy & Physiology I - Unit II: Homeostasis and Adaptation

• Homeostasis is the process of maintaining a controlled, stable internal environment in an organism.
• The term "homeostasis" comes from the Greek words "homeo" (same) and "stasis" (to stay).
• The internal environment refers to the conditions inside an organism. These conditions remain relatively constant despite changes in the outside environment.
• Homeostatic mechanisms keep the internal environment within certain limits (set points).
• Homeostatic imbalance can lead to disease.
• Homeostasis is essential for normal body functioning and sustaining life. Examples include temperature, pH level, and blood sugar levels.

Body Fluids

• Body fluids are dilute, watery solutions containing dissolved chemicals inside or outside cells. Maintaining their volume and composition is crucial.
• Intracellular fluid (ICF) is the fluid inside cells.
• Extracellular fluid (ECF) is the fluid outside cells.
• Interstitial fluid is ECF found between cells and tissues.
• Examples of important body fluids include blood plasma, lymph, cerebrospinal fluid (CSF), synovial fluid, and aqueous humor.

Factors Affecting Homeostasis

• Disease
• Stress
• Lifestyle factors (e.g., diet, smoking, drinking)
• Injury
• Illness (e.g., fever, infection)
• Dehydration
• Starvation
• Environmental temperature

Feedback Mechanisms

• Feedback mechanisms are physiological regulatory systems that return the body to a normal internal state (homeostasis).
• A feedback mechanism is activated by a change in the system, which triggers an output.
• The most important function of a feedback mechanism is to bring the body's state into a stable state.

Components of Feedback Mechanisms

• Receptor: A structure that monitors internal functions and conditions; detects changes in the internal environment.
• Control center: Receives messages from receptors about any change in internal conditions and compares the change to the set point.
• Effector: Receives messages from the control center to adjust its function to correct deviations from the set point.

Types of Feedback Mechanisms

• Negative feedback systems: These systems reverse a change, acting to maintain stability. A change in the body prompts a response that counteracts the change, returning the body to its normal state. Examples include maintaining body temperature.
• Positive feedback systems: These systems strengthen or reinforce a change. A change in one part of the body triggers a response that intensifies the change. An example is childbirth.

Role of Homeostasis

• No specific organ solely controls homeostasis; many organs contribute, especially the brain.
• Different systems (skin, kidneys, liver, endocrine, nervous, and sensory systems) play roles in maintaining internal conditions within narrow limits.
• Examples: Body temperature regulation, maintaining blood sugar, removal of waste products, etc.
• Body temperature regulation: The body maintains a relatively constant internal temperature (usually 37°C), despite wider external temperature fluctuations. The body achieves this through mechanisms such as sweating, vasodilation, vasoconstriction, and shivering. - Sweating helps cool the body by evaporative cooling. - Vasodilation increases blood flow to the skin, allowing heat to dissipate. - Vasoconstriction decreases blood flow to the skin, conserving heat. - Shivering produces heat through muscle contractions.
• Homeostatic Example (Urea): Cells produce nitrogenous waste (urea) during protein breakdown. The kidneys remove urea waste from the body to prevent its accumulation in the cells, which would be dangerous.