1. Human Anatomy and Physiology
Pick up the handout.
Bring up your ecology worksheets to be stamped.

2. Homework Human Body Systems due Friday.
You need to know these for MCAS.
You need MCAS to graduate high school.
Therefore, you need to do this homework this week. Use your textbooks and/or internet resources to complete the work.
Five body systems in four nights. Get at least one system done every night.

3. Objectives Define homeostasis.
Describe the basic function of a physiological feedback loop.
Give an example of a positive and a negative feedback loop.

4. Levels of Organization
Does anybody recall the different levels of organization of living things? Starting with the smallest:
Cell organelle
_____

5. Levels of Organization
Does anybody recall the different levels of organization of living things? Starting with the smallest:
Cell organelle
Cell
_____

6. Levels of Organization
Does anybody recall the different levels of organization of living things? Starting with the smallest:
Cell organelle
Cell
Tissue
_____

7. Levels of Organization
Does anybody recall the different levels of organization of living things? Starting with the smallest:
Cell organelle
Cell
Tissue
Organ
_____

8. Levels of Organization
Does anybody recall the different levels of organization of living things? Starting with the smallest:
Cell organelle
Cell
Tissue
Organ
Organ System
_____

9. Levels of Organization
Cell organelle
Cell (ex: a cardiac muscle cell)
Tissue = A group of cells carrying out a specific function. (ex: a layer of heart muscle tissue)
Organ = A group of tissues carrying out a general function. (ex: the heart)
Organ System = A group of organs carrying out a major function. (ex: the cardiovascular system)
Organism

10. Central Theme
We learned a general overview of how cells maintain their lives, we learned a general overview of how structures like organs and the organization of tissues developed through time, and the focus in this unit is on:
HOMEOSTASIS
(don’t suppose anybody remembers this word? Break it down, what might it mean?)

11. Central Theme
HOMEOSTASIS: Regulation of the internal environment to achieve a stable, constant condition.
Maintaining a stable body temperature, energy, pH, etc. Basically, keeping the body at the level of stability that permits survival.
The organ systems are all about the different ways that parts of the body contribute to maintaining homeostasis.

12. Homeostasis
For instance, maintaining a stable, constant level of blood sugar, anyone know anything about that?

13. Homeostasis
A significant way that this is done is through physiological feedback loops.
What’s feedback?
What’s a loop?

14. Homeostasis
A physiological feedback loop is the body regulating itself in response to a stimulus.
Two kinds: positive and negative feedback loops.

15. Homeostasis
Positive feedback loop: In response to a rising level of the input, you get more of the output.
What ever is out of balance becomes more out of balance.
A positive feedback loop, in terms of the body, more often than not disrupts homeostasis rather than maintains it.
So-called “vicious cycle.”

16. Positive Feedback Loops
Another example: oxytocin stimulating contractions

17. Negative Feedback Loop
Negative feedback loop: In response to a rising level of the input, you decrease the output.
Whatever is out of balance becomes less out of balance.
Essential to maintaining homeostasis.

18. Negative Feedback Loop
Another example is body temperature.
As temp rises, nerves signal capillaries to dilate, which releases some heat.
When temp is too low, other nerves signal capillaries to contract, conserving heat.

19. Feedback Loops From those examples:
Were positive feedback loops always doing good things?
Were negative feedback loops always doing bad things?

20. Feedback Loops From those examples:
Were positive feedback loops always doing good things?
Were negative feedback loops always doing bad things?
Positive vs. Negative isn’t about good or bad, it’s about escalation or stabilization.

21. Feedback Loops
To get used to the idea of a feedback loop, I want you to think of at least four more, two positive and two negative.
They don’t have to be physiological. They could be human activities, environmental, something from a movie or video game, anything.
Diagram each one, and label them as positive or negative. Handed in for credit.
Grade not given for beautiful art or anything, just for whether or not I can tell that yes, this is a negative feedback loop.