Return toward the set point.

Homeostasis maintains internal conditions within useful limits, not at a perfectly fixed value. Receptors detect change, a control centre compares the signal with a set point, and effectors respond.

In negative feedback, the response opposes the initial change. When body temperature rises, sweating and increased blood flow near the skin promote heat loss. A falling temperature evokes a different response.

INTERACTIVE MODEL

Thermoregulation

Balanced responseBody temperature37 °C34 °C41 °C

Explore: Disturb the set point and see the compensating response change direction.

\text{change}\to\text{sensor}\to\text{effector}\to\text{opposing response}

WORKED EXAMPLE

Body temperature climbs above its usual range.

Thermoreceptors detect the increase and signal control centres.
Sweating increases evaporation, tending to lower temperature.

Assumed knowledge

Cause-and-effect sequences.

Learning checkpoints & source

YOUR LEARNING CHECKPOINT

Trace receptor, control centre and effector.
Distinguish negative from positive feedback.

QCAA Biology · Unit 2 · Homeostasis ↗

READY TO TRY IT?

Return toward the set point.

Thermoregulation

Body temperature climbs above its usual range.

Put the idea to work.