1. Homeostasis: staying within limits

2. News paper Article……. What happened? What part of the body does it affect?

3. Body cells require a relatively stable internal environment for normal functioning The external environment is composed of the environment. The internal environment is the liquid. This includes tissue fluid and plasma.

4. Extra- and intracellular fluids Tissue fluid and plasma move. 3 examples include: Nutrients & gas that pass from tissue fluid to blood Waste products from tissue to blood Oxygen from tissue to cells

5. Homeostasis: keeping within limits Despite changes in the external environment, the internal environment of living things remains fairly constant. The maintenance of a constant internal environment is known as homeostasis.

6. Systems involved in homeostasis The systems involved include:  Circulatory system  Respiratory system  Urinary system  Nervous system  Hormonal  Digestive  Skin

7. Variables associated with homeostasis Nutrients Ions (Na +, Ca +, Cl - ) Water Blood volume Red blood cells Temperature Oxygen levels

8. Task Explain why each of the above variables is important in maintaining stability.

9. Detecting and Responding In order to maintain stable conditions, organisms need to: Detect changes Counteracting change This type of control is known as negative feedback.

10. Negative Feedback

11. What variables are controlled by negative feedback? Blood glucose levels Temperature Water balance Oxygen concentration pH levels etc

12. Hormones in action Controlling blood glucose levels The hormones involved in controlling this variable are insulin and glucagon. These hormones are produced in the pancreas.

13. Blood glucose levels Insulin – controls how much glucose is absorbed, from the blood, by the cells Glucagon – notifies the liver to release glucose into the blood

14. Blood glucose levels Alpha cells – increase production of glucagon which acts on the liver to convert glycogen to glucose Beta cells – decrease production on insulin. Therefore less glucose will be absorbed by the cells

15. If the blood glucose levels fall…

16. Cells involved.... Beta cells Reduces insulin in the blood Less glucose being absorbed Blood glucose levels rise

17. Cells involved.... Alpha cells increases glucagon production which acts on the liver Liver converts glucagen into glucose Blood glucose levels rise

18. If the blood glucose levels rise…

19. Cells involved.... Beta cells Increase insulin in the blood More glucose being absorbed Blood glucose levels falls

20. Cells involved.... Alpha cells Decrease glucagon production which acts on the liver Blood glucose moves into liver and converted to glucogen Blood glucose levels falls

21. Example

22. Positive Feedback The change is encouraged Example is child birth

23. Cell Communication Multicellular organisms are composed of many cells. Communication can either be Chemical Electrical They are referred to as signalling molecules

24. Hormones as cell communicators This is an example of cell communication Hormones can travel different distances  Action on the same cell  Diffusion through tissue fluid (action on nearby cells)  Transport through the blood stream (action on distant cells

25. Hormones are diffused through the body Cells have receptors which are specific to each hormone. Cells can either have one or many different kinds of receptors for different hormones

26. Different types of hormones There are three types of hormones Amino derivatives Steroid hormones Peptide hormones

27. Amino Acid derivatives When are they made… Made in advance by cells and then stored Life span Short life span Solubility Water soluble Example Alanine

28. Steroid hormones When are they made… Made on demand Life span Long life span Solubility Lipid soluble Example Estrogen

29. Peptide hormones When are they made… Made in advance by cells and then stored Life span Short life span Solubility Water soluble Example Antidiuretic hormone

30. Steroids have a lipid base, therefore are referred to as hydrophobic (lipophilic) and is insoluble in water A carrier protein is needed for this hormone to travel through the blood stream.

31. Amino acid derivatives & peptide hormones are hydrophilic and is soluble in water. No assistance to travel through the bloodstream Unable to pass through the membrane without assistance A G-protein is needed to transmit their message The difference is how they enter their target cell.

32. General Pathway  Hormone binds to receptor on cell membrane or within cell  Signal detected within cell  Signal transduction a series of events that changes the signal received by the cell  Cell activates response to signal

33. Hormones in plants Plant growth and development is influenced by both internal and external factors Internal factors include: chemicals External factors include: light, gravity, temperature & day length

34. Tropisms Plants that respond to external factors are known as tropisms. Some include Phototropism Geotropism Thigmatropism Photoperiodism

35. Phototropism External Factor Light Hormone involved Auxin Response Plant moves towards the light

36. Geotropism External Factor gravity Hormone involved Auxin Response Roots grow towards the earth Shoots grow towards the sky

37. Thigmotropism External Factor touch Hormone involved Auxin Response Plant grows along like a vine

38. Photoperiodism External Factor Amount of day light Hormone involved florigen Response Flowers open and close to increase pollination

39. Plant hormones Plant hormones are produced by plant cells and in relatively small amounts. They travel via the phloem and xylem and act on other cells in the plants

40. Plant hormone classification Plant hormones are grouped into the following five groups  Auxin  Cytokinins  Gibberellins  Ethylene  Abscicic acid

41. Auxin Produced in… The tip of the coleoptile Evidence… Tips were removed and grow no longer occurred When tip was placed onto agar, which was then placed onto coleoptile without a tip it grew

42. Auxin Function at low concentration Enlarges and elongates cells Stimulates elongation of young developing shoots and roots Involved in fruit development.

43. Auxin Function at high concentration Inhibits growth in roots

44. IAA… Indoleacetic acid Influences growth and development in plants (enlargement and elongation of plant cells)

45. Apical Dominance Lateral buds do not grow and the concentration of growth is located at the apex (top/tip) of the plant If tip removed lateral buds will grow

46. Tip removed from a growing shoot If the tip is removed growth will no longer occur This is because auxin is stored in the tip. When removed no cell development occurs

47. If tip is removed and placed onto a piece of agar that auxin store in the tip will diffuse into the agar When agar is placed onto the growing shoot (tip removed) the shoot will continue to grow What does this experiment illustrate?

48. Phototropism Plants move towards the sunlight. Why? To obtain more light, so that photosynthesis is maximised

49. Stimulus: Light How does it work? Coleoptile A Light is evenly dispersed Therefore auxin is evenly dispersed Coleoptile grows straight Coleoptile B Light is concentrated on one side Auxin moves away from light source (ie dark side) Highly concentrated on the darker side causes cells to elongate and grow faster than the other side. This causes the shoot to bend towards the light

50. Positive phototropism moves towards the light Negative phototropism moves away from the light

51. Worksheet… Investigating phototropism page 19 Hormonal plants – plant growth regulators page 28 - 29

52. Geotropism Roots and shoots will change direction if a pot is turned on its side. Why? So that roots will direct itself to water and shoots towards light

53. Stimulus: Gravity How does it work? Roots Gravity is concentrated on the lower side Auxin is concentrated on the lower side which cause inhibition of cell growth Upper side grows fast causing it to turn Shoots Auxin accumulation in the shoots on the lower side Increases cell growth and elongation Shoot bends upwards

54. Positive geotropism moves towards the gravity Negative geotropism moves away from the gravity

55. Worksheet… Investigating geotropism page 21

56. Cytokinins Produced in The roots and can be translocated to the shoots Its function is to… Growth promoting hormone which acts on shoots, roots and fruits promote cell division and differentiation

57. Gibberellins Produced in The seed Its function is to… Stimulate stem elongation by stimulating cell division and elongation. Stimulates bolting/flowering in response to long days. Breaks seed dormancy and initiate bud development Stimulates enzyme production (a-amylase) in germinating cereal grains for mobilization of seed reserves. Can delay aging in leaves and citrus fruits.

58. Abscisic Acid Produced in The leaves Its function is to… Stimulates the closure of stomata Inhibits shoot growth but will not have as much affect on roots or may even promote growth of roots. Induces seeds to synthesize storage proteins. Has some effect on induction and maintenance of dormancy.

59. Ethylene Produced in A variety of tissue type Its function is to… Stimulates the release of dormancy. Stimulates shoot and root growth and differentiation (triple response) Stimulates leaf and fruit abscission. Stimulates flower opening. Stimulates flower and aging. Stimulates fruit ripening.

60. Nervous System Is composed of the brain, spine and nerves around the body They are categorised into the following groups  Central nervous system  Peripheral nervous system