Homeostasis Flashcards
What is homeostasis?
The maintenance of a stable internal state
What is negative feedback?
A physiological response in the opposite direction to a change (shivering when cold)
What are the different systems for negative feedback?
Sensor, integrator and effector
What is the purpose of a sensor?
Detects a change
What is the purpose of an integrator?
Compares the change from a set-point
What is the purpose of an effector?
Induces response to get back to set-point
What is antagonistic control?
Changes of a variable in both directions (shivering when cold and sweating when hot)
Disadvantages of negative feedback
- Delays in response as integrator needs time to detect a change
- Delay when stopping negative feedback as effector needs time to stop the change
- May not occur in extreme conditions
Adaptations of negative feedback
Anticipation: predicts changes before they occur and can stop negative feedback before it overshoots the set-point
Acclimatisation: adaptation that alters negative feedback gradually (adding fat layers in autumn to get ready for winter)
Changing set points
Set points can change temporarily, permanently or cyclically
What is positive feedback?
A physiological response in the same direction as a change
What is enantiostasis?
Maintaining homeostasis by changing one physical variable due to a change in another variable
3 classes of animals for homeostasis
Conformers- internal state matches external environment (most animals)
Regulators- maintain constant internal state (mammals)
Avoiders- maintain internal state by avoiding environmental change (migrators)
The cell
- Smallest unit of organisation capable of processes associated with life
- Obtain nutrients and energy sources, produce energy, eliminate waste and synthesise protein to maintain shape and for cellular function
- Maintain constant internal state and can control exchange molecules
Examples of specialised cells
Gland cells (secretion of molecules), neurons (electrical conductivity), kidney cells (material exchange) and muscle cells (movement)
Tissue
Groups of cells with similar specialised functions which are used to make up organs
Organism
Collection of systems (2 or more organs) separate from external environments
Difference between single cell organisms and animals
Single cell organisms regulate via direct contact with exterior whereas animals regulate via no contact with exterior. Single cell organisms are surrounded by an internal fluid to undergo homeostasis.
Intrinsic vs Extrinsic
Intrinsic: regulated by one tissue type or organ (quick)
Extrinsic: regulated by different organ systems (slow)
Control systems
Regulate homeostasis indirectly via other systems (nervous and endocrine systems)
Maintenance systems
Regulates homeostasis directly (Respiratory, circulatory, digestive,
excretory, integumentary and immune system)
