Quick questions on Homeostasis, feedback, thermoregulation and osmoregulation: HSC Biology Module 8

<!-- Diagram: negative feedback loop, deep palette | reviewed 2026-06-28 --> <svg class="fig" viewBox="0 0 440 520" role="img" aria-labelledby="nf2-t nf2-d"> <title id="nf2-t">The five-component negative feedback loop, stacked vertically</title> <desc id="nf2-d">A vertical loop. A stimulus changes a variable away from its set point. A receptor detects the change and signals the control centre (such as the hypothalamus). The control centre activates an effector (a muscle or gland).

Blood glucose is held near 5 mmol/L by two opposing pancreatic hormones - the clearest example of hormonal (not neural) homeostatic control.

Osmoregulation is the control of water and solute balance. The control centre is the hypothalamus, and the effector is the kidney via antidiuretic hormone (ADH, vasopressin).

Animals are not the only organisms that manage water balance. A plant must open its stomata to take in CO2 for photosynthesis, but open stomata also lose water vapour by transpiration. Maintaining water balance means controlling that loss.

Skin thermoreceptors detect cold. The hypothalamus triggers:

Skin and hypothalamic thermoreceptors detect heat. The hypothalamus triggers:

A feedback answer that stops at "the effector responds" loses the final mark - state that the response returns the variable to the set point and the loop switches off (negative feedback).

When the question contrasts two systems (e.g. temperature vs glucose), explicitly pair nervous-fast-electrical against hormonal-slow-chemical; that paired contrast is where the marks sit.