1. Topic 12: The Human Body, Homeostasis, & Feedback Mechanisms

2. The Human Body
Human require many systems for digestion, respiration, reproduction, circulation, excretion, movement, coordination, & immunity
The components of the human body, from organ systems to cell organelles, interact to maintain homeostasis.

3. What is Homeostasis?
The maintenance of a constant environment in the body.
Achieved by many different internal controls mechanisms that detect deviations and make corrective actions.
If there is a disruption in any human body system there may be a corresponding disruption in homeostasis

4. 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 OR Dynamic Equilibrium

5. Homeostasis
In order to maintain homeostasis the body uses feedback loops. There are 2 types of feedback loops:
Negative
Positive

6. Negative Feedback
It is a process by which a receptor, an integrator and an effector detects processes and responds to a change in a body constant so that a reverse affect takes place.
Negative feedback is when the response is opposite to the stimulus.
This allows the body to stay constant (maintain homeostasis)

7. Negative Feedback
A good example of negative feedback is the cruise control in my car.
A good thing to use if you have a “heavy foot!!”
The cruise control has a sensor that senses the speed of the car as well as a control mechanism that processes the information from the sensor. It then adjusts the speed of the car by manipulating the accelerator.
Okay but where is the negative part?

8. Negative Feedback Continued
If I go downhill the car naturally speeds up a bit. The sensor senses this and the controller decreases the speed by easing up on the accelerator.
Can you see that the response (slowing down) is opposite to the stimulus (speeding up)?

9. Negative Feedback Continued
Likewise as the car goes uphill and slows down a bit. The cruise control works the accelerator to increase the speed.
Again the response (speeding up) is opposite of the stimulus (slowing down).
This is negative feedback in action.

10. Examples of Homeostasis & Negative Feedback Mechanisms
Temperature Regulation
Regulation of Blood Sugar Levels
pH Balance
……and remember the stomates and guard cells in plants

11. Negative Feed Back: Human Body Temperature Regulation
Humans maintain a relatively constant body temperature of about 37° C.
when we "heat up" we sweat if possible
the evaporation of this perspiration returns the body to its original temperature

12. Receptor Proteins
Receptor Proteins are the 1st part of a feedback loop, and are found in every cell, in every organ & tissue.
Send nerve impulses to brain as a result of environmental stimulants.
For example: receptor proteins on skin cells detect changes in temperature and send that information to the brain.
If nerve or hormone signal are blocked, cellular communication is disrupted and homeostasis is affected.

13. Outside Cell
Cell
Membrane
Receptor Protein
Inside Cell

14. Integrator (The Brain)
2nd part of negative feedback loop
Sends messages to glands, muscles and/or organs
The brain receives information from the receptor proteins and sends a message to either the sweat glands or the muscle cells.

15. Effector (part of the body)
3rd part of negative feedback loop.
Receptor proteins receive info from brain causing a change in internal conditions.
Sweat glands enable the body to cool off when they produce sweat and muscle cells enable the body to warm up when they contract (shivering).
Hair follicle
1 - Sweat gland
2 - Sebaceous gland
3- Muscle 3

16. RECEPTOR PROTEINS
( ON CELLS)
EFFECTORS
(PARTS OF BODY)
RESPONSE=SWEAT
EFFECTORS
(PARTS OF BODY)
RESPONSE =
SHIVERING
Heat
Lost
Heat
Gained
INTEGRATOR
(BRAIN)

17. Negative Feedback Loop: Home heating system
Thermostat is set at a desired temp.
Furnace turns on and heats the house to desired temp
When desired temp is reached the furnace turns off.
The house cools & temp drops below the desired temp. the furnace turns on & the house warms back up to desired temp.

18. Negative Feedback Controlling Glucose Levels
Your cells also need an exact level of glucose in the blood.
Excess glucose gets turned into glycogen in the liver
This is regulated by 2 hormones (chemicals) from the pancreas called:
Insulin
Glucagon

19. Increase in Blood Glucose Level
After eating blood glucose level increases
Brain sends message to pancreas to release insulin into blood
Insulin allows body cells to absorb glucose
Insulin also stimulates the liver to convert some glucose into glycogen ( a form of stored energy)
The result…..blood glucose level decreases & homeostasis occurs.

20. Glycogen
If there is too much glucose in the blood, Insulin converts some of it to glycogen
Insulin
Glucose in the blood

21. 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 Type 1 DIABETES.
Diabetics have to inject insulin into their blood, continually monitor their blood glucose levels, and be careful of their diet.
Diabetes can lead to other health conditions including glaucoma & poor circulation.

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

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

24. Decrease in Blood Glucose Level
Negative Feedback:
Decrease in Blood Glucose Level
After not eating for a while blood glucose level decreases.
Brain sends a message to the pancreas to release glucagon ( a type of protein) into the blood
Glucagon stimulates the liver to convert glycogen (stored energy) into glucose
Glucose levels in the blood increases & the body returns to homeostasis

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

26. Body Systems Involved in Blood Glucose Regulation
Endocrine system: produces insulin and glucagon (hormones/proteins)
Circulatory System: transports hormones (insulin & glucagon), glucose & glycogen to cells in the body.
Nervous System: stimulates a response by sending and receiving messages to & from cells….as a result glucose levels increase or decrease.

27. Acids/ Bases/pH Scale pH levels must be maintained
Especially for digestion to work properly
pH Scale:
Indicates the
concentration of H+ ions in
solution

28. Acids Bases pH of less than 7 (Example: HCl)
pH of greater than 7 (Example: Bleach, Ammonia

29. Buffers To test for acid & bases: Litmus paper base = blue acid = red
Weak acids or bases that can react with strong acids or bases to prevent sharp changes in pH.
These are important for maintaining a constant internal environment…..homeostasis (between 6.5 and 7.5 for most cells)
Think of treatments used for stomach aches
For digestive enzymes to work properly, pH balance must be maintained
To test for acid & bases: Litmus paper
base = blue acid = red

30. Remember…Homeostasis in Plants
Negative Feedback Mechanism
Maintenance of Water
plants need to regulate water loss and carbon dioxide intake for photosynthesis and other life activities
when plants do not keep enough water in their cells, they wilt and die
stomate: a microscopic hole in a plant leaf which allows gases to enter and leave and water vapor to leave as well. Stomata is the plural of stomate.
guard cells: open and close the stomate.
the ability of the guard cell to close during periods of limited water availability for the plant allows the plant to maintain water homeostasis

31. Positive Feedback Mechanisms
Positive feedback is where the response is the same as the stimulus.
In positive feedback the response can be magnified.

32. Positive Feedback Mechanisms
A good example of positive feedback is the feedback you hear from sound systems in concerts.
In this example the stimulus (sound going into microphone) is processed to produce a magnified response (sound coming out of the speakers).
Sometimes the microphone picks up sound from the speakers and continues to magnify it until it is out of control (the feedback that hurts your ears).
Example in Humans:
Oxytocin & Child Labor

33. Positive Feedback in the Human Body
The release of oxytocin to intensify the contractions that take place during childbirth.[
In positive feedback the response can be magnified.

34. Name 2 systems that work together.
Circulatory – respiratory
Skeletal – muscular
Digestive – circulatory
Nervous – muscular
Integumentary – circulatory
Endocrine – circulatory
Excretory - circulatory
How do they work together? ……. You will investigate through your project & presentation!!