GCSE Biology: Homeostasis and Response

Homeostasis is the body's crucial ability to maintain stable internal conditions, essential for cell function, through coordinated nervous and hormonal systems. This cheat sheet covers key aspects of human and plant responses.

Core Principles

• Homeostasis maintains optimal conditions for enzyme action and all cell functions, including temperature, pH, and nutrient levels.
• Control systems involve receptors detecting changes, coordination centers processing information, and effectors (muscles/glands) restoring balance.
• The nervous system provides rapid responses via electrical impulses along neurones, coordinated by the CNS (brain and spinal cord).
• The endocrine system uses hormones for slower, longer-lasting responses, with glands secreting chemicals into the bloodstream.
• Reflex actions are automatic, rapid responses that bypass conscious brain processing for immediate protection.
• Plant hormones like auxins, gibberellins, and ethene regulate growth, tropisms, and fruit ripening.

Formulas

• stimulus $\rightarrow$ receptor $\rightarrow$ coordinator $\rightarrow$ effector $\rightarrow$ response