Homeostasis
🔹 Core Definition & Importance
Term: What does homeostasis literally mean?
Definition: Standing still or remaining unchanged.
Term: Homeostasis
Definition: The condition of optimal functioning for an organism.
Term: What is the body constantly working to maintain?
Definition: A stable internal environment and adjustment to continual changes in external conditions.
Term: What must be maintained for homeostasis to occur?
Definition: A number of conditions or factors within the body must be maintained within an optimal physiological range.
Term: Examples of variables maintained within an optimal physiological range
Definition: Core body temperature, fluid balance, blood sugar levels.
🔹 Levels of Homeostasis
Term: At what levels must homeostasis be maintained?
Definition: Organism level, organ level, and cellular level.
Term: Organism level example of homeostasis
Definition: Maintaining an overall body temperature of 36–37°C.
Term: Organ level example of homeostasis
Definition: The stomach maintaining a particularly acidic pH to carry out digestion.
Term: Cellular level example of homeostasis
Definition: Cells maintaining specific ion concentrations to support their function.
🔹 Homeostatic Regulatory Systems
Term: What maintains homeostasis for each variable?
Definition: A state-of-the-art regulatory system that constantly monitors conditions, detects when things are going awry, and triggers an appropriate response to restore the status quo.
Term: Which systems are involved in homeostatic regulation?
Definition: The nervous system, the endocrine system, or both.
🔹 Components of a Homeostatic Regulatory Mechanism
Term: What are the three components of homeostatic regulators?
Definition: Receptor (sensor), control centre, effector.
Term: Receptor (sensor)
Definition: Detects changes in conditions.
Term: Control centre
Definition: Receives and processes information and decides how the body will react to restore homeostasis.
Term: Effector
Definition: Responds to commands from the control centre and carries out a response to counteract the original change.
Term: Feedback
Definition: The relationship between sensory receptors and responding effectors.
🔹 Negative vs Positive Feedback
Term: Negative feedback
Definition: Occurs when the actions of the effector oppose the changing conditions that have occurred.
Term: Is negative feedback common?
Definition: Yes, it is the primary or most common mechanism of homeostatic regulation.
Term: Positive feedback
Definition: Occurs when the actions of the effector magnify or enhance the changing conditions.
Term: How does positive feedback differ from negative feedback?
Definition: Negative feedback opposes the initial stimulus, whereas positive feedback amplifies the initial response.
Term: When does positive feedback typically occur?
Definition: When a potentially dangerous or stressful process must be completed quickly.
🔥 Negative Feedback Example: Body Temperature
Term: Homeostatic range for body temperature
Definition: Generally between 36 and 37°C.
Term: What happens when body temperature exceeds 37°C?
Definition: Sensors detect the change and report it to temperature control centres in the brain.
Term: Effectors involved in temperature regulation
Definition: Blood vessels and sweat glands.
Term: What responses occur to reduce high body temperature?
Definition: Blood vessel dilation and increased sweat production.
Term: What is the outcome of these responses?
Definition: Loss of heat and reduction in body temperature to restore homeostasis.
Term: What happens when temperature drops back below 37°C?
Definition: Sensors stop reporting the threat and the negative feedback loop shuts off.
🔥 Positive Feedback Example: Blood Clotting
Term: What triggers haemostasis (blood clotting)?
Definition: Blood exiting a blood vessel due to injury.
Term: What are platelets?
Definition: Tiny fragments of cells constantly travelling around in the blood.
Term: What is the initial response to a damaged blood vessel?
Definition: Platelets are recruited to physically plug the damage.
Term: How is blood clotting an example of positive feedback?
Definition: Activated platelets secrete factors that recruit more and more platelets, enhancing the response.
Term: When does the positive feedback process stop?
Definition: When the stimulus is no longer present and homeostasis is restored.
🧠 Concept Integration Card (High-Level Understanding)
Term: Why is maintaining homeostasis complex?
Definition: Because many constantly changing conditions such as environmental exposure, diet, nutrition, and physical activity impact the internal environment.