1. Homeostasis Talkie time and Recap
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2. Competencies:
explain how some organisms maintain steady internal conditions that possess various structures and processes (STEM_BIO11/12-IVi-2)
2. describe examples of homeostasis (e.g., temperature regulation, osmotic balance and glucose levels) and the major features of feedback loops that produce such homeostasis (STEM_BIO11/12-IVi-3)

3. (15 mins) Film Viewing
Buzz Session
1. What is Homeostasis?
2. How does our body maintain balance?
3. Re-Explain the example in the video about homeostasis?
4. Can you give or think of another example?

4. Physiology Science of body functions Teleological vs Mechanistic views
Teleological – the why, explains purpose of a physiological process
Mechanistic – the how, explained in terms of cause and effect of physiological process
Example: shivering
Teleological - shivering elevates a low body temperature
Mechanistic - when body temperature drops below normal, a reflex pathway causes involuntary oscillating skeletal muscle contractions which produce heat

5. Levels of Organization
Chemical
Cellular
Tissue
Organs
System Level
Organismic Level

6. Levels of Structural Organization
Chemical Level - atomic and molecular level
Cellular level - smallest living unit of the body
Tissue level
Group of cells and the materials surrounding them that work together on one task
4 basic tissue types: epithelium, muscle, connective tissue, and nerve

7. Levels of Structural Organization
Organ level - consists of two or more types of primary tissues that function together to perform a particular function or functions
Example: Stomach
Inside of stomach lined with epithelial tissue
Wall of stomach contains smooth muscle
Nervous tissue in stomach controls muscle contraction and gland secretion
Connective tissue binds all the above tissues together
System - collection of related organs with a common function, sometimes an organ is part of more than one system
Organismic level - one living individual

8. Body Systems
Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of the whole body
Do not act in isolation from one another
Human body has 11 systems

9. Body Systems

10. Body Systems

12. Homeostasis
Defined as maintenance of a relatively stable internal environment
Does not mean that composition, temperature, and other characteristics are absolutely unchanging
Homeostasis is essential for survival and function of all cells
Each cell contributes to maintenance of a relatively stable internal environment

13. Basic Cell Functions
Sensing and responding to changes in surrounding environment
Control exchange of materials between cell and its surrounding environment
Obtain nutrients and oxygen from surrounding environment
Eliminate carbon dioxide and other wastes to surrounding environment
Perform chemical reactions that provide energy for the cell
Synthesize needed cellular components

14. Homeostasis
Body cells are in contained in watery internal environment through which life-sustaining exchanges are made
Extracellular fluid (ECF) - Fluid environment in which the cells live (fluid outside the cells)
Two components:
Plasma
Interstitial fluid
Intracellular fluid (ICF) - Fluid contained within all body cells

15. Homeostasis

16. Balancing the Internal and External Environment
Cells, the fundamental units of life, exchange nutrients and wastes with their surroundings:
The intracellular fluid is “conditioned by”…
the interstitial fluid, which is “conditioned by” …
the plasma, which is “conditioned by” …
the organ systems it passes through.
ICF
ISF
plasma
organs
external
environment
internal environment

17. Homeostasis
Homeostasis involves dynamic mechanisms that detect and respond to deviations in physiological variables from their “set point” values by initiating effector responses that restore the variables to the optimal physiological range.
Two systems that maintain homeostasis are: Nervous system & Endocrine system

18. Maintenance of Homeostasis
Nervous system
Controls and coordinates bodily activities that require rapid responses
Detects and initiates reactions to changes in external environment
Endocrine system
Secreting glands of endocrine regulate activities that require duration rather than speed
Controls concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume and electrolyte composition

19. Homeostasis Factors homeostatically regulated include
Concentration of nutrient molecules
Concentration of water, salt, and other electrolytes
Concentration of waste products
Concentration of O2 = 100mmHg and CO2 = 40 mmHg
pH = 7.35
Blood volume 4-6 L and pressure 120/80
Temperature = 37o C

20. Control of Homeostasis
Homeostasis is continually being disrupted by
External stimuli
heat, cold, lack of oxygen, pathogens, toxins
Internal stimuli
Body temperature
Blood pressure
Concentration of water, glucose, salts, oxygen, etc.
Physical and psychological distresses
Disruptions can be mild to severe
If homeostasis is not maintained, death may result

21. Control of Homeostasis

22. Homeostatic Control Systems
In order to maintain homeostasis, control system must be able to
Detect deviations from normal in the internal environment that need to be held within narrow limits
Integrate this information with other relevant information
Make appropriate adjustments in order to restore factor to its desired value

23. Homeostatic Control Systems
Control systems are grouped into two classes
Intrinsic controls
Local controls that are inherent in an organ
Extrinsic controls
Regulatory mechanisms initiated outside an organ
Accomplished by nervous and endocrine systems

24. Homeostatic Control Systems
Feedforward - term used for responses made in anticipation of a change
Feedback - refers to responses made after change has been detected
Types of feedback systems
Negative
Positive

25. Feedback Loops: Types Negative feedback loop Positive feedback loop
original stimulus reversed
most feedback systems in the body are negative
used for conditions that need frequent adjustment
Positive feedback loop
original stimulus intensified
seen during normal childbirth

26. Negative Feedback Loop
Negative feed back loop consists of:
Receptor - structures that monitor a controlled condition and detect changes
Control center - determines next action
Effector
receives directions from the control center
produces a response that restores the controlled condition

27. Negative Feedback Loop

28. Negative Feedback Loop

29. Homeostasis – Negative Feedback Loop
Blood glucose concentrations rise after a sugary meal (the stimulus), the hormone insulin is released and it speeds up the transport of glucose out of the blood and into selected tissues (the response), so blood glucose concentrations decrease (thus decreasing the original stimulus).

30. Homeostasis of Blood Pressure
Baroreceptors in walls of blood vessels detect an increase in BP
Brain receives input and signals blood vessels and heart
Blood vessels dilate, HR decreases
BP decreases

31. Positive Feedback during Childbirth
Stretch receptors in walls of uterus send signals to the brain
Brain induces release of hormone (oxytocin) into bloodstream
Uterine smooth muscle contracts more forcefully
More stretch, more hormone, more contraction etc.
Cycle ends with birth of the baby & decrease in stretch

32. Role of Body Systems in Homeostasis

33. Glossary Maintain – keep up. Constant – the same.
Internal – inside the body.
Environment – surroundings of the body.
Feedback - a cycle in which the output of a system “feeds back” to modify or reinforce the actions of the system in order to maintain homeostasis.

34. Glossary
Negative feedback - a change causes system 1 to send a message to system 2 to restore homeostasis. When system 1 detects that system 2 has acted, it stops signaling for action and system 2 stops (turned off).
Positive feedback - the original stimulus is promoted rather than stopped. Positive feedback is rarely used to maintain homeostasis. An example of positive feedback is childbirth.

35. What is Homeostasis? Body cells work best if they have the correct
Temperature
Water levels
Glucose concentration
Your body has mechanisms to keep the cells in a constant environment.

36. What is Homeostasis?
The maintenance of a constant environment in the body is called Homeostasis

37. Controlling body temperature
All mammals maintain a constant body temperature.
Human beings have a body temperature of about 37ºC.
E.g. If your body is in a hot environment your body temperature is 37ºC
If your body is in a cold environment your body temperature is still 37ºC

38. Controlling body temperature
Animals with a large surface area compared to their volume will lose heat faster than animals with a small surface area.
Volume = _______
Surface area = ______
Volume : Surface area ratio = ___________
Volume = _______
Surface area = ______
Volume : Surface area ratio = ___________

39. Controlling body temperature
Volume : Surface area ratio = 1:6
Volume : Surface area ratio = 1:5
For every 1 unit of heat made, heat is lost out of 6 sides
For every 1 unit of heat made, heat is lost out of 5 sides

40. Controlling body temperature
Volume : Surface area ratio = 1:6
Volume : Surface area ratio = 1:5
The bigger the Volume : Surface Area ratio is, the faster heat will be lost.

41. Penguins huddling to keep warm

42. What mechanisms are there to cool the body down?
Sweating
When your body is hot, sweat glands are stimulated to release sweat.
The liquid sweat turns into a gas (it evaporates)
To do this, it needs heat.
It gets that heat from your skin.
As your skin loses heat, it cools down.

43. Sweating
The skin

44. What mechanisms are there to cool the body down?
Vasodilation
Your blood carries most of the heat energy around your body.
There are capillaries underneath your skin that can be filled with blood if you get too hot.
This brings the blood closer to the surface of the skin so more heat can be lost.
This is why you look red when you are hot!

45. This means more heat is lost from the surface of the skin
If the temperature rises, the blood vessel dilates (gets bigger).

46. What mechanisms are there to warm the body up?
Vasoconstriction
This is the opposite of vasodilation
The capillaries underneath your skin get constricted (shut off).
This takes the blood away from the surface of the skin so less heat can be lost.

47. This means less heat is lost from the surface of the skin
If the temperature falls, the blood vessel constricts (gets shut off).

48. What mechanisms are there to warm the body up?
Piloerection
This is when the hairs on your skin “stand up” .
It is sometimes called “goose bumps” or “chicken skin”!
The hairs trap a layer of air next to the skin which is then warmed by the body heat
The air becomes an insulating layer.

50. Controlling Glucose levels
Your cells also need an exact level of glucose in the blood.
Glucose moves into the cells for cellular respiration
Excess glucose gets turned into glycogen in the liver
This is regulated by 2 hormones (chemicals) from the pancreas called:
Insulin
Glucagon

51. If there is too much glucose in the blood, Insulin converts some of it to glycogen the rest moves into the cells for use in cellular respiration.
Glycogen
Insulin
Glucose in the blood

52. Glycogen
If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose.
Glucagon
Glucose in the blood

53. Diabetes Some people do not produce enough insulin.
When they eat food, the glucose levels in their blood cannot be reduced.
This condition is known as DIABETES.
Diabetics sometimes have to inject insulin into their blood. They have to be careful of their diet.

54. Glucose levels rise after a meal.
Insulin is produced and glucose levels fall to normal again.
Glucose
Concentration
Normal
Time
Meal eaten

55. Meal eaten Glucose levels rise after a meal. Diabetic
Concentration
Diabetic
Insulin is not produced so glucose levels stay high
Time
Meal eaten

56. Insulin The glucose in the blood increases.
Glycogen
The glucose in the blood increases.
But there is no insulin to convert it into glycogen.
Glucose concentration rises to dangerous levels.
Insulin
Glucose in the blood

57. Blood Glucose Feedback Mechanism
Pancreas produces Insulin
Glucose into cells
Out of blood
Blood glucose increases Homeostasis Blood glucose decreases
( High ) (Low)
Glucose out of cells
Into blood
Pancreas produces Glucagon

58. Controlling water levels
The control of water levels is carried out by the KIDNEYS.
It is closely linked to the excretion of urea.
Urea is a waste product that is made when the LIVER breaks down proteins that are not needed by the body.
Urea contains the element Nitrogen.

59. The kidneys
The kidneys “clean” the blood of waste products and control how much water is kept in the body. The waste products and water make up urine which is excreted via the ureter.
“Dirty” blood enters the kidney through the renal artery. Then, several things happen to clean the blood...

60. 1. Filtration
Blood enters the tubule area in a capillary.
The capillary forms a small “knot” near the kidney tubule.
The blood is filtered so all the small particles go into the tubule.
The capillary then carries on to run next to the tubule.

61. The kidney tubule now contains lots of blood components including:
Glucose:
Ions:
Water:
Urea:

62. 2. Reabsorb sugar
The body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.

63. 2. Reabsorb sugar
The body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.

64. 3. Reabsorb water
Water and ions are the next to be absorbed. It depends on how much is needed by the body.

65. 3. Reabsorb water
Water and ions are the next to be absorbed. It depends on how much is needed by the body.

66. Reabsorbing water
If you have too little water in your blood, you will produce very concentrated urine.
(very little water in it)
If you have too much water in your blood, you will produce very dilute urine.
(lots of water in it)

67. 5. Excrete the waste
Everything that is left in the kidney tubule is waste:
All the urea
Excess water
This waste is called urine. It is excreted via the ureter and is stored in the bladder.
Renal vein
The “clean” blood leaves the kidney in the renal vein.
Ureter

68. Summary of urine production
Urea is a waste product made in the LIVER
Water content of the body is controlled in the KIDNEYS
Urea, water and other waste makes up URINE.
Urine travels down the URETER and is stored in the BLADDER
Urine is excreted through the URETHRA.

69. Temperature regulation, glucose level control and water level control are all examples of NEGATIVE FEEDBACK MECHANISMS.

70. Application Explain the Diagram