2. chapter 1-2: Homeostasis
Essential Question:
Explain why it is so important for feedback mechanisms to monitor the Necessary Life Functions and Survival Needs in living things.
chapter 1-2: Homeostasis
Learning Target
Describe each Necessary Life Function.
Describe each of the Human Survival Needs for human life.
Define homeostasis.
Explain positive feedback.
Explain negative feedback.

3. Don’t forget to chunk your notes!

4. overview
Homeostasis: the ability to maintain a relatively stable internal environment.

5. overview
Homeostasis is a dynamic state of equilibrium.

6. overview
Chemical, thermal (temperature), and neural (nerve) factors maintain homeostasis.

7. Don’t forget to chunk your notes!

8. Necessary life functions
Processes the body must do to keep us alive are maintaining boundaries, movement, responsiveness, digestion, metabolism, excretion, reproduction, & growth.

9. Necessary life functions
Maintaining Boundaries: the internal environment remains distinct from the external
Cellular Level: accomplished by plasma membranes
Organismal Level: accomplished by the skin

10. Necessary life functions
Movement: locomotion, propulsion (peristalsis), and contractility

11. Necessary life functions
Responsiveness: ability to sense changes in the environment and respond to them

12. Necessary life functions
Digestion: breakdown of ingested foodstuffs

13. Necessary life functions
Metabolism: all the chemical reactions that occur in the body

14. Necessary life functions
Excretion: removal of wastes from the body

15. Necessary life functions
Reproduction: creating new life on the cellular and organismal levels
Cellular: an original cell divides and produces two identical daughter cells
Organismal: sperm and egg unite to make a whole new person

16. Necessary life functions
Growth: increase in size of a body part or of the organism

17. Don’t forget to chunk your notes!

18. Survival needs
Nutrients, oxygen, water, normal body temperature, & appropriate atmospheric pressure are needed for humans to survive. All must be in appropriate amounts.

19. Nutrients: chemical substances used for energy and cell building
Survival needs
Nutrients: chemical substances used for energy and cell building

20. Oxygen: needed for metabolic reactions
Survival needs
Oxygen: needed for metabolic reactions

21. Water: provides the necessary environment for chemical reactions
Survival needs
Water: provides the necessary environment for chemical reactions

22. Survival needs
Maintaining Normal Body Temperature: necessary for chemical reactions to occur at life-sustaining rates

23. Survival needs
Atmospheric Pressure: the appropriate pressure required for proper breathing and gas exchange in the lungs

24. Don’t forget to chunk your notes!

25. Homeostatic control mechanisms
A variable or stimulus produces a change in the body.

26. Homeostatic control mechanisms
The three components of control mechanisms are:
Receptor: monitors the environments and responds to changes (stimuli)
Control center: determines the set point at which the variable is maintained
Effector: provides the means to respond to the stimuli
Homeostatic control mechanisms

27. Homeostatic control mechanisms
The three components of control mechanisms are:
Receptor: monitors the environments and responds to changes (stimuli)
Control center: determines the set point at which the variable is maintained
Effector: provides the means to respond to the stimuli
Homeostatic control mechanisms

28. Homeostatic control mechanisms
The three components of control mechanisms are:
Receptor: monitors the environments and responds to changes (stimuli)
Control center: determines the set point at which the variable is maintained
Effector: provides the means to respond to the stimuli
Homeostatic control mechanisms

29. Homeostatic control mechanisms
The three components of control mechanisms are:
Receptor: monitors the environments and responds to changes (stimuli)
Control center: determines the set point at which the variable is maintained
Effector: provides the means to respond to the stimuli
Homeostatic control mechanisms

30. Homeostatic control mechanisms
The three components of control mechanisms are:
Receptor: monitors the environments and responds to changes (stimuli)
Control center: determines the set point at which the variable is maintained
Effector: provides the means to respond to the stimuli
Homeostatic control mechanisms

31. Homeostatic Control Mechanisms3
Input: Information sent along afferent pathway to
Control center 4
Output: Information sent along efferent pathway to
Effector
Receptor (sensor) 2
Change detected by receptor 5
Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis
Stimulus: Produces change in variable 1
Imbalance
Variable (in homeostasis)
Imbalance
Figure 1.4

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33. Feedback loops or mechanisms
The body monitors itself.

34. Feedback loops or mechanisms
It turns on and off mechanisms as needed.

35. Feedback loops or mechanisms
They either increase or decrease an effect.

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37. Negative feedback
In negative feedback systems, the output shuts off the original stimulus.

38. Negative feedback
Example: Regulation of blood glucose levels

39. Figure 1.5

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41. positive feedback
In positive feedback systems, the output enhances or exaggerates the original stimulus.

42. Example: Regulation of blood clotting.
positive feedback
Example: Regulation of blood clotting.

43. Figure 1.6

44. Don’t forget to chunk your notes!

45. Homeostatic imbalance
Disturbance of homeostasis or the body’s normal equilibrium.

46. Homeostatic imbalance
Overwhelming of negative feedback mechanisms allows destructive positive feedback mechanisms to take over.