1. Module 5- 5.1.1 Communication and Homeostasis By Ms Cullen

2. Survival In order to survive living organisms must respond to their external environment. Animals can respond by their behaviour or their physiology. Organisms also need to respond to changes in their internal environment, as conditions need to be optimal for their metabolism. Any change in the internal or external environment of an organism is called a stimulus. Plants coordinate responses to stimuli by plant hormones (covered in module 5.1.5)

3. Give some examples of both external and internal stimuli that organisms have to respond to and their responses.

4. Receptors detect stimuli Relate the following words to what you know about receptors: specific cells proteins effectors response muscle cells glands.

5. Enzymes What internal conditions are needed to be kept constant to allow enzymes to work efficiently? - - - -

6. Maintaining the internal environment - Homeostasis Homeostasis is Greek meaning ‘steady state’. In animals, cells and tissues are surrounded by tissue fluid – so this is the internal environment. Cells will alter their own internal environment as they use up substrates and release products. For example: CO 2 as it is released as waste will change the pH of the tissue fluid and this could inhibit enzyme action. The blood maintains the composition of the tissue fluid, transporting substances and making sure waste products are excreted. This of course needs to be closely monitored.

8. Homeostasis What conditions need to be kept constant in the human internal environment? - - - - - -

9. Coordination Multicellular organisms are more efficient as their cells are able to differentiate. However, this means that there needs to be good communication between different parts of the body. What qualities do you think a communication system should have? - - - - -

10. Cell Signalling Cells communicate by one cell releasing a chemical, which is detected and responded to by another cell, the target cell. Cell signalling can be local between adjacent cells, for example neurotransmitters at synapses of neurones. Or between distant cells, using hormones, for example ADH released from the pituitary gland affects cells in the kidney to maintain water balance. There are 2 major systems of communication that work by cell signalling: 1.The neuronal system 2.The hormonal system http://learn.genetics.utah.edu/content/cells/cellcom/ Compare and contrast the 2 systems.

11. Comparison of neuronal and hormonal communication NeuronalHormonal(endocrine) Message is: Transmission route Effects

12. Homeostasis works on the principles of Negative and Positive Feedback Negative feedback mechanisms restore the systems to their normal level. Examples would be ADH controlling the amount of water in the blood, insulin controlling the amount of glucose in the blood. Positive feedback mechanisms takes levels further away from the norm. It is the opposite of negative feedback in that encourages a physiological process or amplifies the action of a system. Examples would be platelets accumulating to clot blood, the release of oxytocin to increase muscle contractions during birth. Positive feedback can be harmful too an example would be an increase in body temperature leading to a fever.

13. Thermoregulation

14. Maintaining body temperature - Thermoregulation Enzymes control metabolic reactions and they work at an optimum temperature. Therefore bodies need to be kept as close to that temperature as possible. The optimum core body temperature (areas more than 2.5cm below the body surface) for humans is about 36.9˚C. There are 2 main methods of thermoregulation for organisms. 1.Ectothermy (=outside heat) 2.Endothermy (=inside heat)

15. Ectotherms Ectotherms maintain their body temperature by their behaviour. They derive their body heat from their immediate external environment, which of course fluctuates daily and seasonally.

16. Ectotherms - lifestyle 1.The North American horned lizard spends nights buried in the sand to prevent heat loss. 2.Early morning the lizard basks on a rock, with its back 90˚ to the sun to get maximum heat absorption. 3.When body temperature is reached the lizard will become active and feed. 4.When the ground becomes very hot the lizard lies in shade. 5.The lizard will dig into the sand early in the evening whilst it is still warm. http://www.bbc.co.uk/nature/adaptations/Thermophile#p00c28lf

17. Endotherms All mammals and birds are endotherms. Most of their heat is derived internally from respiration. They control their core body temperature by a combination of physiology and behaviour. As they are able to maintain a body temperature independent of their immediate environment this has allowed endotherms to colonise areas of extreme temperatures.

18. Endotherms Emperor penguins can maintain a body temperature of 38˚C in the Antarctic where temperatures regularly fall as low as -60˚C Find out: Why don’t penguins feet freeze?

19. Can you think of advantages and disadvantages of being an endotherm?

20. Advantages of being endothermic

21. Disadvantages of being endothermic

22. How does size affect endotherms? Heat is lost from the body surface. So a small endotherm with a large surface area to volume ratio will lose heat more quickly. Therefore smaller endotherms must respire more rapidly to release enough heat energy to balance the heat loss. This requires a higher metabolic rate and intake of food.

23. How does size affect endotherms? There is a minimum size that an endotherm can be, below which it would be impossible to eat enough food to maintain body temperature. Savi’s Pygmy Shrew is thought to be the smallest mammal, weighing between 1.2 and 2.7g. The smallest bird is the Bee Humming bird, weighing about 2g.

24. How does size affect endotherms? Once endotherms are a certain volume body shape can influence the surface area to volume ratio and therefore heat loss. The rounder the shape, the smaller the surface area to volume ratio and the easier it is to conserve heat. Animal which live in hotter areas tend to have long noses, big ears and flaps of skin which increase their surface area to volume ratio and heat loss. Elongated extremities also have larger surface areas aiding heat loss.

25. How does size affect endotherms? Which cow lives in the hot climate? How is it adapted? http://www.bbc.co.uk/nature/adaptations/Psychrophile#p00f2926

26. How does size affect endotherms?

27. Endotherms – Physiological mechanisms to maintain body temperature Explain how the following respond if core body temperature is too low and too high. Sweat glands Lungs, mouth and nose Hairs on skin Arterioles leading to capillaries in the skin Liver cells Skeletal muscles

28. (a) Vasodilaton; (b) vasoconstriction

29. Endotherms – Behavioural mechanisms to maintain body temperature Can you think of behavioural mechanisms which endotherms use if they are too hot or too cold? - - - -

30. Detecting Temperature Change The peripheral temperature receptors in the skin detect external changes in temperature. The hypothalamus in the brain monitors blood temperature. If core body temperature drops then the hypothalamus sends signals to reverse this change; Increase in metabolic rate, increased muscle contraction & decrease in loss of heat to the environment. If core temperature rises above the optimum the hypothalamus sends signals to bring about opposite changes. This is an example of negative feedback.

31. Controlling body temperature by negative feedback Name the effectors involved

32. Peripheral temperature receptors These are in the skin and they monitor the temperature of the extremities. This information is sent to the hypothalamus. If the brain receives information that the external environment is too hot or too cold then it can initiate behavioural mechanisms to rectify this.

33. In a cold environmentIn a warm environment Increase in heat productionNo increase in heat production Decrease in heat loss (heat conservation)Increase in heat loss

34. Were dinosaurs endotherms or ectotherms?

35. Why Don’t Penguin’s Feet Freeze?