CIE IGCSE Biology

Revision Notes

14.2.3 Homeostasis: Temperature Control

The Skin & Homeostasis

  • Control of body temperature is a homeostatic mechanism
  • Homeostasis is the maintenance of a constant internal environment
  • This means that internal conditions within your body (such as temperature, blood pressure, water concentration, glucose concentration etc) need to be kept within set limits in order to ensure that reactions in body cells can function and therefore the organism as a whole can live
  • The human body maintains the temperature at which enzymes work best, around 37°C
  • If body temperature increases over this temperature, enzymes will denature and become less effective at catalysing reactions such a respiration

Structure of the Skin

A cross-section of human skin, IGCSE & GCSE Biology revision notes

A cross-section of human skin

Regulating Temperature: Basics

  • Regulation is controlled by the brain which contains receptors sensitive to the temperature of the blood 
  • The skin also has temperature receptors and sends nervous impulses to the brain via sensory neurones
  • The brain responds to this information by sending nerve impulses to effectors in the skin to maintain the temperature within a narrow range of the optimum, 37°C
  • Fatty tissue under the dermis acts as a layer of insulation to prevent too much body heat being lost through the skin

Regulating body temperature, IGCSE & GCSE Biology revision notesHomeostatic responses to changes in body temperature

Responses to changes in temperature:

Homeostasis-Temperature Control table, IGCSE & GCSE Biology revision notes

Extended Only

Vasodilation & Vasoconstriction

  • When we are cold blood flow in capillaries slows down because arterioles leading to the skin capillaries get narrower – this is known as vasoconstriction
  • This reduces the amount of heat lost from blood by radiation as less blood flows through the surface of the skin
  • When we are hot blood flow in capillaries increases because blood vessels to the skin capillaries get wider – this is known as vasodilation
  • This cools the body as blood (which carries heat around the body) is flowing at a faster rate through the skin’s surface and so more heat is lost by radiation

Responses in the skin when hot, IGCSE & GCSE Biology revision notesResponses in the skin when hot

Responses in skin when cold, IGCSE & GCSE Biology revision notesResponses in the skin when cold

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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