1. Homeostasis Chapter 9 http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/homeo/homeosts.shtml

2. Homeostasis  Physiological state of the body  Internal physical and chemical conditions are maintained within a tolerable range  Includes  Temperature, hormone levels, pH, pressure, concentrations of glucose and other solutes in the blood

3. Internal Environment  Extracellular fluid  Interstitial fluid – fills the spaces between cells and tissues (e.g. plasma)  Consists of water, sugars, salts, FA, AA, coenzymes, hormones, neurotransmitters, waster products  Regulates flow of chemicals and allows cells to function properly  Lymphatic system transports fluid throughout the body 

4. Internal Environments  Changes in Extracellular Fluid has negative effects on cellular function  Body uses organ systems to regulate internal conditions  Nervous system  Endocrine system  Muscular system  Integumentary system  Excretory system  Reproductive system

5. Nervous System  Brain, spinal cord, peripheral nerves, sensory organs  Receives sensory data from the environment  Informs body of external conditions  Transmits signals throughout the body

6. Endocrine System  Pituitary, thyroid, pancreas, adrenal (glands)  Regulates levels of hormones and other chemicals

7. Excretory System  Kidneys, bladder, urethra, ureters  Rids the body of waste  Maintains clean internal environment

8. Integumentary System  Skin, sweat glands, hair, nails  Maintains a constant body temperature

9. Immune System  White blood cells  Protects/fights infection

10. Digestive System  Liver  Breaks down amino acids  Detoxifies harmful chemicals (alcohol)  Manufactures important proteins

11. Homeostatic Mechanisms  Respond to internal and external conditions  Feedback systems – Positive/Negative  Help bring the body back into balance  Breathing rate, heart rate, internal temperature, blood glucose levels

12. Negative Feedback  Reduces the output or activity of an organ or system back to its normal range  Include 3 elements  Sensor  tissues or organs - detects change  Integrator - hypothalamus  control centre – compares conditions from environment with to optimal conditions in the body  Set points – ranges of values which need to be maintained  Effector  returns measured condition back to set point – response  Antagnositc effectors – produce opposite effect of change detected

18. Hypothalamus  Body’s thermostat  Maintains body temperature  Optimal body temperature – 35 ⁰ - 37.8⁰  Body temp falls → vasoconstriction in skin/shivering→ reduced blood flow→ less thermal energy lost to environment → body temp increases  Body temp rises → blood vessels dilate/induce vasodilation/sweating → increase blood flow→ increase thermal energy loss to environment→ body temp decreases  Signals from hypothalamus make us aware of our own temperature

19. Positive Feedback Mechanisms  Increases change in environmental condition  Does not result in homeostasis  Cause system to become unstable  “fight or flight” response  reproduction  fever  Positive feedback mechanisms operate within negative feedback mechanisms  Allows body to be brought back into balance

21. Thermoregulation  Internal temperature regulation  Negative feedback mechanism  Thermoreceptors – compare external temp with internal set point  Trigger responses (2)  Rate of exothermic reactions in body (metabolism)  Rate of thermal energy exchange through surface of body

23. Mechanisms of Thermal Energy Exchange  Occurs at the surface where body comes into contact with the external environment  Exchange of thermal energy occurs through 1 of 4 mechanisms  Conduction  Convection  Radiation  Evaporation  All of these mechanisms act simultaneously

24. Conduction  Flow of thermal energy between molecules that are in direct contact

25. Convection  Transfer of thermal energy within a fluid (liquid or gas)

26. Radiation  Thermal energy is transferred electromagnetically

27. Evaporation  Absorbs thermal energy from skin via water/sweat

28. Homeotherms  Animals that maintain a stable internal temperature regardless of external conditions  Includes  Poikilotherms  Endotherms  Ectotherms

29. Poikilotherms  Fish, amphibians, reptiles, and most invertebrates  Body temperature varies with and often matches the temperature of the external environment

30. Endotherms  Warm blooded animals (mammals, birds)  Homeotherms that use internal physiological mechanisms (metabolism) to generate thermal energy and maintain body temp  Remain fully active over a wide range of temperatures  Need a constant supply of energy

32. Ectotherms  Cold blooded animals (reptiles, amphibians, fish)  Homeotherms that use external sources of energy to absorb thermal energy and regulate body temperature  Temperature fluctuates with environmental temperature  Inactive when temp are too low  Undergo thermal acclimatization  Gradual adjustment to seasonal temp

33. Torphor, Hibernation, Estivation  Adaptations to survive extreme climates by conserving energy  Torphor  Sleeplike state  Metabolic rate and body temperature drop in response to daily temp (nocturnal animals, hummingbird)  Hibernation  State of inactivity over an extended period of time  Estivation  Seasonal torphor – environment is hot and water is scarce

34. Water Balance  Extracellular fluid needs to maintain a constant volume (~15L) of water and balance of solute within the body  Mechanism  Osmosis

35. Osmosis  Water molecules move from a high concentration to a region of lower concentration across a selectively permeable membrane  Osmotic pressure  Results from a difference in water concentration gradient between the two sides of the selectively permeable membrane  Hyperosmotic  Hypoosmotic  Isoosmotic

36. Hyperosmotic  Solution with higher concentration of solute molecules  Water tends to move to this side

37. Hypoosmotic  Solution with lower concentration of solute molecules  Water tends to move from this solution

38. Isoosmotic  Solution with the same solute and water concentrations

39. Osmoregulation  Process of actively regulating the osmotic pressure of bodily fluids  Extracellular fluid = intracellular fluid (isoosmotic)  [solute] remains the same  [water] remains the same

40. The Excretory System  Main functions (with the help of osmoregulation)  Concentrate wastes and expel them from the body  Regulate fluids and water within the body  Organs included  Kidney  Adrenal gland  Ureter  Urinary bladder  Urethra

41. Removal of Metabolic Waste WasteOrigin of WasteOrgan of Excretion AmmoniaBreakdown of amino acids in the liver kidneys UreaConversion of ammonia in the liver kidneys, skin Uric AcidBreakdown of purines in food and drink kidneys Carbon DioxideCellular respiration (breakdown of glucose) lungs, intestines, skin Bile PigmentsBreakdown of porphyrin ring (hemoglobin) intestines Lactic AcidCellular respiration (breakdown of glucose) kidney Solid WasteBreakdown of foodintestine

42. Kidneys  Removes waste  Balances blood pH  Maintain body’s water balance  Blood is supplied to kidney via renal artery  Re-enters circulatory system via renal vein

43. Nephrons  Functional unit of the kidney (1 000 000 per kidney)  Regulate water balance  Conduct excretion  Different sections of the nephron have specialized functions in formation of urine and conservation of water  http://www.youtube.com/watch?v=oXcEAH_yesY

44. Urinary Bladder  Renal pelvis connects the kidney to the ureter which fills the bladder  Holds ~300mL-400mL of urine before exiting the urethra

45. Deamination  Occurs in the liver – breakdown of protein  Removal of amino group from amino acid  Creates ammonia NH ₃ (toxic to body)  Urea Cycle  Ammonia reacts with bicarbonate and 2 ATP molecules to form urea  Transported to kidneys where excretion occurs via blood

46. Bicarbonate Buffer System  Maintains pH of blood (acid-base homeostasis)

47. Formation of Urine  Ultimate goal – conserve water, balance salts, concentrate wastes  Urine – hypoosmotic to surrounding body fluids - water tends to move from urine into the body fluids  3 Feature of nephron interact to achieve ultimate goal  Arrangement of loop of Henle  Difference in permeability  Concentration gradient of molecules and ions  3 processes interact to achieve formation of urine  Filtration  Reabsorption  Secretion

48. Formation of Urine: Overall Process

49. Filtration  Begins at Bowman’s capsule (selectively permeable membrane)  Receives water, ions, glucose, AA and urea from glomerulus  Difference of pressure allows for transfer of molecules and ions into capsule  1400L of blood pass through kidneys every day  Bowman’s capsule filters ~180L from blood  ~1.5L is excreted as urine daily

50. Reabsorption  Occurs as fluid from Bowman’s capsule enters proximal convoluted tubule, Loop of Henle and distal convoluted tubule  Water, ions and nutrients are transferred back into interstitial fluid and peritubular capillaries via passive and active transport  Microvilli inside tubules increase surface area  Difference in solute concentration allows water to move across the membrane and back into interstitial fluid via osmosis (aquaporins)

51. Secretion  Removal of waste products from the blood and interstitial fluid and secreted into the nephron  Include – detoxified poisons, water soluble drugs, metabolites, H ⁺  Secretion of H ⁺ ions balances acidity in body  Reabsorption of HCO ₃⁻ occurs simultaneously  Buffer system controls pH levels of blood  Increased acidity – H ⁺ excreted as urine  Urine reaches bottom of collecting ducts, flows into renal pelvis, through ureters, into urinary bladder and exits through urethra

53. Kidneys Regulate Blood Oxygen Levels  Kidneys monitor blood oxygen levels (RBC’s)  If too low – kidneys release erythropoetin (EPO) into the blood stream which stimulates the production of red blood cells

54. Kidney Diseases  Renal Failure  2 types  Acute – rapid progressive loss of renal function  Injuries, accidents, complications from surgery  Chronic – slow progressive with long term consequences  Diabetes mellitus, uncontrolled hypertension, polycystic kidney diseases  Treatments  Dialysis  Kidney transplant