Human Body Responses To the environment

1. Homeostatis Introduction You will be able to… • Lesson Objectives • By the end of the lesson I can: • Plan and implement an investigation • Recall how environmental conditions affect the human body • Explain how the body controls its internal environment Human Body Responses To the environment

2. Key Words • Vasodilation • Vasoconstriction • Homeostasis • Piloerection • Dilate • Capillaries

3. Starter Put these events into order they occur • Blood vessels vasodilate so more blood is carried to surface to lose heat. • Blood capillaries vasoconstrict so less blood is carried near surface to keep in heat • Sweating is reduced • Sweating is increased • Hairs stand up to trap warm air to act as an insulator • Hairs lie flat • No shivering • Shivering – muscle action produces heat from respiration

4. Controlling Conditions - the basics • Internal conditions that are controlled include; • Water content • Ion content • Temperature • Blood sugar level • Water is leaving the body all the time as we breathe out and sweat. We lose any excess water in the urine (produced by the kidneys). We also lose ions in sweat and urine. • We must keep out temperature constanst otherwise the enzymes in the body will not work properly, if at all. • Sugar in the blood is the energy source for cells. The level of sugar in our blood is controlled.

5. How does the body stay cool? > Sweating • When you are hot, sweat glands are stimulated to release sweat. • Heat energy from your skin is used to turn the liquid sweat into gas - sweat evaporates. • Because heat is lost, your skin cools down. > See this in action

6. How does the body stay cool? > Sweating Heat lost as sweat evaporates Skin Heat

7. How does the body stay cool? > Vasodilation • Your blood carries most of the heat energy in your body. • There are small blood vessels called capillaries just underneath your skin. • When you are hot, these capillaries get wider (dilate)so more blood comes close to the surface of the skin and heat is lost. • This is why some people go red when they are hot! > See this in action

8. How does the body stay cool? > Vasodilation Heat loss Skin Capillaries

9. How does the body stay warm? > Vasoconstriction • This is basically the opposite of vasodilation. • When you are cold, the capillaries near the surface of your skin get narrower (constrict) and some shut off. • This means less blood comes near the surface of the skin and less heat is lost. • This is why your fingers and toes might go white when they are cold! > See this in action

10. How does the body stay warm? > Vasoconstriction Less heat loss Skin Capillaries

11. ARGH!

12. What do birds do to keep warm when it is cold? I was not scared! (phew!)

13. How does the body stay warm? > Piloerection • When you are cold, the hairs on your skin stand up. • The hairs trap a layer of air next to the skin, which is warmed by body heat and becomes an insulating layer. • This is sometimes called ‘goose bumps’. • The same principle applies to birds or mammals fluffing themselves up. > See this in action

14. How does the body stay warm? > Piloerection Trapped air forms insulation Hairs Skin

15. Investigation planning Aim: The effects of insulation on heat loss Equipment: • 2 conical flasks of the same size • Boiling water • Cotton wool • 2 thermometers • Timer or clock • Graph paper Method: • Obtain 2 conical flasks • Wrap cotton wool round one flask and leave the other uncovered • Pour the same amount of boiling water into both flasks • Place a thermometer in each and record the temperature at 1 min intervals for 15 mins • Record results in a suitable table and plot a graph (put temperature on the vertical axis and time on the horizontal axis)

16. Results Table

17. Graph • What makes a good graph? • Use a Sharp Pencil and a Ruler • Label the axes with Quantity and Unit (e.g. Time / minutes) • The scale on each axis must use up more than half of the graph paper • For line graphs • Plot your points with crosses (X)

18. What is wrong with this graph?

19. Results Analysis What did you measure? What did your results show? Conclusion: What did you find out? How does this link in with vasodilatation and vasoconstriction? What effect did insulation have on the rate of heat loss? Which flask lost heat faster and why? Which structures in the mammal do you think acts in the same way as the cotton wool? Evaluation How could you improve your experiment? Was this a fair test? Were the results accurate? What improvements could be made to further improve the reliability of results?

20. HOMEOSTASIS research Go to http://www.teachersdomain.org/resource/tdc02.sci.life.reg.bodycontrol/ Read the text on the right hand side then Press ‘VIEW’ HAVE YOU GOT WHAT IT TAKES TO CONTROL YOUR BODY MANUALLY? Use the internet to research -how the body is controlled, -why its important and -how it occurs. You should include water, ion, temperature and blood sugar levels. Place your research into a self-designed table on the computer and save it.

21. Homeostatis Introduction You will be able to… • Lesson Objectives • By the end of the lesson I can: • Plan and implement an investigation • Recall how environmental conditions affect the human body • Explain how the body controls its internal environment Human Body Responses To the environment