D3.3 Homeostasis
Homeostasis maintains internal conditions through feedback control of blood pH, glucose, temperature, kidney filtration, osmoregulation and blood flow in human physiology.
- Syllabus
- First assessment 2025
- Topic
- D3.3
- Level
- SL
Exam analysis
Chance of appearing30%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper2
Typical marks1–3
Most tested objectives
Common question formats
- Definition or recall
- Process explanation
- Data analysis
- Diagram interpretation
- Calculation
- Structured response
Recent exam appearances
November 2025Paper2 ["SL"] · TZ16(c)[ 4 ]D3.3.1—Homeostasis definition
November 2025Paper2 ["SL"] · TZ16(b)[ 7 ]D3.3.3—Blood glucose regulation
November 2025Paper2 ["SL"] · TZ16(a)[ 4 ]D3.3.2—Negative feedback loops
November 2025Paper1A ["SL"] · TZ121[ 1 ]D3.3.6—Thermoregulation mechanisms
May 2025Paper1A ["SL"] · TZ322[ 1 ]D3.3.6—Thermoregulation mechanisms
Practice this topic
Coverage 2010–2025 · Updated 16 Jul 2026
Objective notes
6 learning objectives• Homeostasis maintains a stable internal environment within narrow limits
• Variables include body temperature, blood pH, glucose, gases, ions, and osmotic concentration
• Negative feedback detects deviation from a set point and reverses it
• Receptors, coordinators, effectors, and feedback loops restore normal conditions
• Beta cells secrete insulin when blood glucose rises
• Alpha cells secrete glucagon when blood glucose falls, affecting liver and muscle stores
• Type 1 diabetes results from autoimmune destruction of pancreatic beta cells
• Type 2 diabetes involves insulin-receptor/response failure and is linked to lifestyle risk factors
• Thermoregulation uses negative feedback to maintain core temperature near 37 °C
• Thermoreceptors signal the hypothalamus, which coordinates skin, muscles, liver, and hormones
• Cooling uses vasodilation, sweating, and hairs lying flat
• Warming uses vasoconstriction, reduced sweating, shivering, metabolic heat, and brown fat