1. Sub-topic (a) Homeostasis
Biological
Systems
Sub-topic (a) Homeostasis

2. Learning Outcome
Give a definition of homeostasis.

3. Homeostasis
Homeostasis is the maintenance of the body’s internal environment despite changes to the external environment.
We need to keep a constant internal environment for the body to work properly

4. What factors do you think must remain constant in our bodies?

5. water balance
temperature
blood sugar

6. Success Criteria
I can give a definition of homeostasis.

7. Learning Outcome
State that the kidneys are the main organs responsible for regulating water balance.

8. Water Balance The human body is made up of 70% water
In order to maintain water balance the amount of water we gain must equal the amount of water we lose on a daily basis

9. Osmoregulation Kidneys regulate the water content of the body.
This process is called osmoregulation.

10. In your groups you have 2mins to write down all of the ways which you think we GAIN and LOSE water.

11. Food Drink Chemical Reactions
Water Gain
Food
Drink
Chemical Reactions

12. Sweat Urine Faeces Breath
Water Loss
Sweat
Urine
Faeces
Breath

13. Human Urinary System
video

14. RENAL ARTERY delivers unpurified blood to the kidney
urethra
vena cava
aorta
RENAL VEIN carries purified blood away from the kidneys
KIDNEYS filter blood for useful and harmful substances + regulate the volume of water in the body
URETER carries urine from the kidney to the bladder
BLADDER short-term storage of urine
URETHRA releases urine from the body
video

15. The kidneys

16. The kidney

17. The kidney
As the renal artery enters the kidney it splits up into a large number of tiny blood vessels called capillaries.

18. The kidney

19. Two important jobs
Filtration
Reabsorption

20. Success Criteria
I can state that the kidneys are the main organs responsible for regulating water balance.

21. Learning Outcome Label the different parts of a kidney nephron.
Describe the functions of the different parts of the kidney nephron.

22. Nephron

23. Glomerulus
The capillary forms a tight knot of blood vessels called the glomerulus.
Blood flows through the glomerulus and is filtered.

24. The blood capillary entering the glomerulus has a wider diameter than the capillary leaving it.

25. Filtration

26. Bowman’s capsule The Bowman’s capsule surrounds the glomerulus.
It collects the liquid filtered out of the blood.
This liquid is called the glomerular filtrate.

27. Filtered or not? Filtered Not filtered Glucose Protein Water
Blood cells
Urea
Salts

30. Reabsorption Completely reabsorbed Variable amounts are reabsorbed
None is reabsorbed
Glucose
Water
Urea
Salts

31. How does a kidney work?

33. Blood is filtered and filtered substances enter the bowman’s capsule
Blood contains useful + waste substances e.g. Glucose, urea, salts and water
Filtrate enters
Only waste substances remain- Urea, some salt, some water
Kidney Tubule- Useful substances are reabsorbed back into the blood (glucose, some water and some salts)
Blood leaving the kidney contains only useful substances (glucose, some water and some salt
Blood capillary- Reabsorbs useful substances

34. Bowmans capsule and down into tubule
From renal
artery
Glomerulus
Bowman’s capsule
Water
Glucose
Urea
all filtered into
Bowmans capsule and down into tubule
Proteins and blood cells too big and remain in blood
Collecting
duct
WATER
reabsorbed.
GLUCOSE
reabsorbed.
Tubule
to renal
vein
URINE: Urea +
excess water
To the URETER

35. Success Criteria I can label the different parts of a kidney nephron.
I can describe the functions of the different parts of the kidney nephron.

36. Samples Experiment
Measure 5 mls of each sample into 3 test tubes labelled A, B and C
Add a few drops of Benedicts solution and place in the water bath.
IF SAMPLE TURNS ORANGE GLUCOSE IS PRESENT
3. Place 0.5ml of each sample AND 0.5ml of urease in a dimple tile
4. Test each with pH paper.
IF PAPER TURNS GREEN UREA IS PRESENT

37. Renal Artery, Renal Vein or Urine?
Glucose present
Urea present
Renal artery
Renal vein
Urine

38. Results and Conclusion
Renal Artery = Sample _______
Renal Vein = Sample _______
Urine = Sample _______
Choose correct answer from the words underlined:
I know sample _________ is from the renal artery because it contained no/both urea and glucose.
I know sample ________ is from the renal vein because it only contained urea/glucose.
I know sample _______ is urine because it contained glucose/urea but did not contain glucose/urea

39. Learning Outcome
Explain the role of ADH in water balance.

40. Anti-Diuretic Hormone (ADH)
This is the hormone that controls how much water is reabsorbed by your kidneys.
ADH

41. ADH
ADH increases the permeability of the kidney tubules which means more water is reabsorbed into the blood stream.

42. Blood capillary
Tubule

43. Blood capillary
Tubule

44. When the water concentration of the blood is too low, a message is sent to the hypothalamus and ADH is released.
This increases the volume of water reabsorbed.
Think – ADH means Anti Drying out

46. Success Criteria
I can explain the role of ADH in water balance.

47. The Nephron Game

48. Learning Outcome
State that the hypothalamus is the area of the brain that controls body temperature.

49. Monitoring body temperature
Body’s temperature monitoring centre is the hypothalamus.

50. Hypothalamus
It receives nerve impulses from thermoreceptors in the skin and the body’s core (i.e. Lungs and heart)
The hypothalamus central thermoreceptors are sensitive to change in blood temperature.

51. Hypothalamus
The hypothalamus then responds by sending out signal via nerve impulses to effectors.
These effectors are mainly in the skin and can bring about correction of body temperature to normal.

52. Success Criteria
I can state that the hypothalamus is the area of the brain that controls body temperature.

53. Learning Outcome Explain the body’s response to overheating.
Explain the body’s response to overcooling.

54. Skin and temperature change
If the body temperature rises the hypothalamus sends a signal to the skin, this causes three responses:
Vasodilation
Increased sweating
Relaxation of hair erector muscles

55. Vasodilation
Vasodilation is the process where small arteries leading to the skin surface dilate.
This increases the diameter of the vessel meaning more blood can flow through.
Heat loss can be increased by conduction and radiation.

57. Increased sweating More sweat is released from the sweat glands.
This coats the skin, and it evaporates by removing heat energy from the skin.

58. Investigating Sweat Results: Method:
Aim: to investigate the effects of sweat on the rate at which a body loses heat
Time (mins)
Temperature (°C)
Dry Tube
Wet Tube 2 4 6 8 10
Method:
Draw a diagram of your experiment.
(25ml of hot water in each boiling tube, one wrapped in dry paper towel, other in damp paper towel. Take temperature then add paper towels and start stop clock - take a temperature reading every 2 minutes)
Conclusion: The water in the wet/dry towelled tube cooled the fastest. This shows that sweat increases/decreases the rate at which the body loses heat

59. Hair erector muscles
Hair erector muscles control the hairs on your body.
When they relax, the hairs lie flat against your skin, this means there is no layer of air to insulate the skin.

60. Skin and temperature change
If the body temperature starts to fall the hypothalamus sends a signal to the skin, this causes three responses:
Vasoconstriction
Decreased sweating
Contraction of hair erector muscles

61. Vasoconstriction
Vasoconstriction is the process where small arteries leading to the skin surface constrict.
This decreases the diameter of the vessel meaning less blood can flow through.
Heat loss by conduction and radiation is therefore decreased.

63. Decreased sweating Less sweat is released from the sweat glands.
This keeps the skin dry and avoids heat loss by evaporation.

64. Hair erector muscles
Hair erector muscles control the hairs on your body.
When they contract, the hairs stand up against your skin, this means there is a layer of air to insulate the skin.

65. Success Criteria I can explain the body’s response to overheating.
I can explain the body’s response to overcooling.

66. LEARNING INTENTIONS
Describe how the body regulates blood glucose levels

67. Blood Glucose Levels
Blood glucose levels in the body must stay at a constant level so that there is always enough glucose in the blood to be delivered to cells for respiration.
2 hormones produced by the pancreas control blood glucose levels – INSULIN and GLUCAGON.

68. Insulin
This is produced by the pancreas. It is carried in the blood to the target organ - liver.
Insulin causes the liver to take up glucose from the blood and convert it to a storage carbohydrate called glycogen and therefore reduces the levels of glucose in the blood.
Insulin
Glucose Glycogen

69. Glucagon
This is also produced by the pancreas. It is carried in the blood to the target organ - liver.
Glucagon causes the liver to convert the storage carbohydrate glycogen to glucose and therefore increases the levels of glucose in the blood.
Glucagon
Glucose Glycogen

70. Eating Less glucose in blood More glucose in blood Exercise
Pancreas makes MORE INSULIN
and
LESS GLUCAGON
Glucose in the blood increases which pancreas detects
Insulin tells the liver to convert more glucose into glycogen
Eating
Less glucose in blood
Normal level of glucose in the blood
Normal level of glucose in the blood
More glucose in blood
Exercise
Glucagon tells the liver to convert more glycogen to glucose
Pancreas makes LESS INSULIN
and
MORE GLUCAGON
Glucose in the blood decreases which pancreas detects

71. LEARNING INTENTIONS
Discuss diabetes and its causes

72. Diabetes
Diabetes is a condition caused by a communication pathway failure which results in;
a fault in release of insulin (type 1) or
a failure to respond to insulin (type 2)

73. Research Task