How does the body hold its core temperature near 37 degrees whether it is freezing or sweltering outside?
Explain how the body regulates core temperature by negative feedback, including the role of the hypothalamus, thermoreceptors and the effectors that control heat loss and heat gain
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on thermoregulation. The hypothalamus and thermoreceptors, the effectors for heat loss (sweating, vasodilation) and heat gain (shivering, vasoconstriction), and the four routes of heat transfer.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
What this dot point is asking
WACE wants you to apply the stimulus-response and negative-feedback model to one named variable, core temperature, naming the receptor, the control centre, and the effectors for both directions. Temperature must be regulated because enzymes work within a narrow range; too hot and enzymes denature, too cold and reactions slow too much.
The control centre and receptors
The hypothalamus is the body's thermostat. It contains the set point (about 37 degrees Celsius) and receives information from two sets of thermoreceptors: peripheral thermoreceptors in the skin that monitor the external temperature, and central thermoreceptors in the hypothalamus itself that monitor the temperature of the blood. The hypothalamus compares this input against the set point and activates the appropriate effectors.
Responding when the body is too hot
If core temperature rises above the set point, the hypothalamus triggers responses that increase heat loss:
- Sweating: sweat glands secrete sweat onto the skin; as it evaporates it carries heat away.
- Vasodilation: arterioles supplying the skin widen, so more warm blood flows near the surface and heat radiates away. This is why pale skin looks flushed when hot.
- Reduced metabolic activity and behaviour: less heat is generated, and behaviours like removing clothing or seeking shade help.
These responses lower core temperature back toward the set point, which is negative feedback because the response opposes the stimulus.
Responding when the body is too cold
If core temperature falls below the set point, the hypothalamus triggers responses that increase heat gain and reduce heat loss:
- Vasoconstriction: arterioles to the skin narrow, so less warm blood reaches the surface and less heat is lost.
- Shivering: rapid involuntary muscle contractions generate heat through respiration.
- Raised metabolic rate: hormones such as thyroxine and adrenaline increase the metabolic rate, producing more heat.
- Erection of body hair (piloerection): traps a layer of insulating air, more useful in furry mammals than in humans.
Routes of heat transfer
Heat moves between the body and the environment by radiation (heat given off as infrared), conduction (direct contact with cooler objects), convection (heat carried away by moving air or water), and evaporation (heat used to evaporate sweat). Sweating relies on evaporation, which is why it is far less effective in humid conditions where sweat cannot evaporate.
How this maps to the exam
Expect to be asked to write the full thermoregulation feedback loop for either heating or cooling, name the control centre and receptors, or explain why a particular effector works (for example why sweating cools or why vasoconstriction conserves heat). You may be asked why sweating is less effective on a humid day, which tests the evaporation route of heat loss.
Exam-style practice questions
Practice questions written in the style of SCSA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WACE 20217 marksOn a very hot day, a person's core body temperature begins to rise. Explain how negative feedback returns core temperature to the set point, naming the receptors, the control centre and at least two effectors and their responses.Show worked answer →
A 7 mark response needs the full loop with two correctly described cooling effectors.
- Stimulus
- Core body temperature rises above the set point of about 37 degrees Celsius.
- Receptors
- Thermoreceptors in the skin and in the hypothalamus detect the rise.
- Control centre
- The hypothalamus compares the value to the set point and coordinates the response.
- Effectors and responses
- Sweat glands increase sweat secretion, and as sweat evaporates it removes heat from the skin (cooling by evaporation). Skin arterioles undergo vasodilation, so more blood flows near the surface and more heat is lost by radiation. Hairs lie flat (relaxed erector pili) to reduce the insulating air layer.
- Feedback
- These responses increase heat loss, so core temperature falls back toward the set point, a negative feedback response because it opposes the rise.
Markers reward thermoreceptors, the hypothalamus, and at least two cooling effectors with the correct mechanism.
WACE 20234 marksExplain two ways the body conserves and generates heat when core temperature falls below the set point on a cold day.Show worked answer →
A 4 mark answer needs two correct heat-conserving or heat-generating responses with mechanisms.
Vasoconstriction. Skin arterioles narrow, so less blood flows near the surface and less heat is lost by radiation, conserving heat.
Shivering. Skeletal muscles contract rapidly and repeatedly, and this muscle activity releases heat through respiration, generating heat.
Other valid points include hairs standing erect to trap an insulating air layer and increased metabolic rate.
Markers reward two distinct responses, each linked to either reduced heat loss or increased heat production.