Notes on Homeostasis, Stimulus–Response Model, and Negative Feedback

Nervous and Endocrine Communication

  • Nervous system: Transmits electrical impulses (action potentials) for fast, short-lived, and highly specific effects.

  • Endocrine system: Transmits hormones via the bloodstream, resulting in slower, longer-lasting, and less tissue-specific responses.

The Stimulus–Response Model

  • Describes how a change (stimulus) is detected and an appropriate response is produced.

  • Components: extStimulus→extReceptor→extControlCentre→extEffector→extResponseext{Stimulus} \rightarrow ext{Receptor} \rightarrow ext{Control Centre} \rightarrow ext{Effector} \rightarrow ext{Response}

Negative Feedback

  • A stimulus–response system where the effector’s response counteracts the original stimulus.

  • Purpose: Maintains homeostasis by returning internal conditions to a set point (e.g., a thermostat moderating temperature).

Homeostasis and the Internal Environment

  • Homeostasis: The maintenance of internal environmental conditions within narrow limits, crucial for cellular function.

  • Internal environment: The fluid surrounding cells (e.g., blood plasma, tissue fluid), distinct from the cytoplasm (intracellular environment).