Do you think ‘The Iceman’ can really will himself to be warmer Do you think ‘The Iceman’ can really will himself to be warmer? In the next 30 sec, list 5 things you might do to try and warm up if you were him…

Share your list with a partner… Are there any similarities? Any things you didn’t think of?

How is that animals are able to maintain their temperature in a range of environments?

Ectotherms Usually at the temperature of their environment Do not have an internal method of heat production Lower energy needs and cells function so slowly at low temperatures they are often inactive during winter

Ectotherms DISADVANTAGES ADVANTAGES Less active in cooler temps May not be capable of activity during winter due to the need to hibernate Ectotherms ADVANTAGES Use less food in respiration Need less food Can use more energy from food for growth

Heterotherms Some ectotherms can sometimes function as endotherms Allows animals to be more active

Endotherms Maintain a relatively constant body temperature Usually higher than their surroundings Generate heat by internal metabolic heat production Have mechanisms by which to regulate loss/gain of heat Endotherms

Endotherms ADVANTAGES Constant temp. DISADVANTAGES Active in cold temp. Can inhabit colder countries Endotherms DISADVANTAGES Lots of energy used to regulate body temp. More food needed Less energy from food goes into growth so more food needed

Regulatory mechanisms These include structures: Feathers Fur Fat Physiological mechanisms Hibernation

A note on terminology… “Cold-blooded” is not correct – their blood will be warm when the environment is warm. “Warm-blooded” is also not correct – a hibernating bat maintains its temperature at about 10 °C.

Explain the graph…

Temperature-regulating Pathways

Thermoregulation Maintenance of body temperature within a range that enables cells to function efficiently The maintenance of body temperature in endotherms is an example of dynamic equilibrium

Sensing: Detecting temperature change

Sensing: Detecting temperature change Involves disturbance and misalignment detectors Temperature receptors in skin (disturbance) Misalignment detectors in the hypothalamus Group of temperature sensitive cells trigger homeostatic responses if blood temperature deviates

Responding: regulating heat exchange Heat loss Radiation Evaporation Conduction Loss of body fluids To the environment Heat gain Metabolism Environmental & behavioural

In a cold environment… We must conserve body heat and gain heat to maintain body temperature Vasoconstriction – blood vessels near the surface of the skin narrow, reducing the volume of blood near the surface, reducing the heat lost to the environment from the blood Shivering – Muscles contract to produce heat via metabolic reactions Hair-raising – muscles in the skin at the base of each hair contract, raising hairs and trapping air, forming an insulating layer. Increased metabolic rate – respiration increases to generate more heat Sweating reduced Behavioural mechanisms – huddling, sheltering

In a hot environment… We must lose body heat to maintain our core temperature Vasodilation – Blood vessels near the surface of the skin dilate and increase in volume, allowing more blood to flow through, radiating heat away through the skin Sweating – water evaporates from the surface of the skin, using heat energy to turn the liquid into water vapour. Prevalent in humans as we lack body hair. In other mammals this takes place from the tongue and mouth Body hair flattening – removes the insulating layer Behaviours – not performing metabolic activity, sheltering

Why do we go pink when we are hot? For you to think about… Why do we go pink when we are hot?

For you to think about…

Over to you… On a piece of paper, list 2 mechanisms the body can use to regulate temperature in a hot environment and in a cold environment…

Your homework task! Compare and contrast a central heating system with your body’s temperature control system. What type of feedback control regulates both these systems? Using Inspiration, illustrate both negative feedback loops involved in thermoregulation. Be sure to include Stimulus, Receptor, Regulator, Effectors. Be detailed and clear. It is up to you whether you present this as a flowchart, picture or concept map!