Notes for Control of Body temperature

Temperature is different in endotherms and ectotherms

Ectotherms are animals that rely on the external environment to control their body temperature as they cannot maintain it internally. E.g Reptiles or insects

Endotherms are animals which can maintain their temperatures internally through the use of feedback mechanisms. E.g humans and birds

Keeping temperature is important in order to make sure enzymes are working at their optimum for cellular reactions like respiration.

There are other differences between ecto and endotherms:

  1. Ectotherms temperature relies on external temperature whilst in endotherms internal temperature is less effected by the outside

  2. Ectotherms activity depends on the outside temp having more energy in high temps but in endotherms they can be active at any temp

  3. Ectotherms have a variable metabolic rate and generate little heat this helps them focus more energy on growth and development rather than in endotherms which have a constantly high metabolic rate and therefore develop energy from that.

Ectotherms then relay on behavioural responses to maintain temp such as basking or hiding inside or increasing/decreasing body temperature.

Mammals have many mechanisms to change body temperature

To increase bodies temperature:

  • Vasoconstriction- to limit heat escaping through skin

  • Shivering- to contract muscles

  • Erector pili muscles on hairs contract to help trap moisture for warmth and to reduce heat loss

  • Sweating less so that heat doesn’t escape via evaporation

  • Hormones- Body releases adrenaline and thyroxine to increase metabolism so more heat is produced

To decrease bodies temperature:

  • Vasodilation- to bring heat to the surface of the skin to evaporate out

  • Sweating- to release water vapour out of the skin to cool it

  • Erector pili muscles on hair relax to provide insulation so less air is trapped and heat is lost easily

  • No sweating

The hypothalamus Controls body temperature in mammals

How the hypothalamus maintains temperature:

Thermoreceptors in the skin detect change in outside temperature sends signals (Using sensory neurone) to the hypothalamus (Detects changes in internal temp) sends signals to effectors using motor neurons which carry out a responds to restore body temperature. E.g to erector pili muscles or blood vessels close to the skin.