1. Physiology Notes and Homeostasis
8/21

2. Bellwork – 12 minutes!
Turn in your homework (staple multiple pages if you have them and write your name on all pages!)
Pick up today’s work
Get a whiteboard, marker and eraser.
Read pg12 – 13 “Homeostasis” through the first 4 paragraphs of “Homeostatic Control Mechanisms”
What is homeostasis? Explain the three elements of the homeostatic control system.

3. Preview
I want you to stand on one foot while I talk. You cannot hold on to anything or switch your foot. You will remain balancing on one foot until I tell you to stop.
If you fall over start again.

4. Announcements QUIZ tomorrow on Word Parts #1
QUIZ Th/F on Chapter 1 terms and homeostasis
Know directional terms, body planes, body cavities and regional terms. You will have to label a body!

5. Preview
Now, keep balancing on one leg, raise it higher! And Close your eyes and listen while I talk.

6. What is homeostasis and how does it work?
Essential Question
Learning Goal:
What is homeostasis and how does it work?
I will be able to describe how homeostasis works using positive and negative feedback mechanisms to keep an organism alive.

7. Agenda 8/22 Homework: Video Physiology Notes Homeostasis Notes
Homeostasis practice
Exit slip
Study Chapter 1
Study for Word Parts Quiz tomorrow!

8. What happened?

9. study of function of body structures
Physiology
defined as
study of function of body structures
Including including
What structures do How they do it
Maintain homeostasis
by regulating: Negative feedback Positive Feedback
Food
Water defined as defined as
Oxygen
Heat Mechanism that Change from normal
Pressure restores body to levels promotes
normal levels further change

10. What is homeostasis?
The bodies ability to maintain a relatively stable internal environment regardless of what is happening outside.
It is keeping balance in the body.
Maintained by the nervous and endocrine systems.

11. Video

12. Variable (in homeostasis)
Figure 1.4, step 1a

13. Variable (in homeostasis)
Stimulus: Produces change in variable
Imbalance
Variable (in homeostasis)
Imbalance
Figure 1.4, step 1b

14. Variable (in homeostasis)
Receptor (sensor)
Change detected by receptor
Stimulus: Produces change in variable
Imbalance
Variable (in homeostasis)
Imbalance
Figure 1.4, step 2

15. Variable (in homeostasis)
Input: Information sent along afferent pathway to
Control center
Receptor (sensor)
Change detected by receptor
Stimulus: Produces change in variable
Imbalance
Variable (in homeostasis)
Imbalance
Figure 1.4, step 3

16. Variable (in homeostasis)
Input: Information sent along afferent pathway to
Control center
Output: Information sent along efferent pathway to activate
Receptor (sensor)
Effector
Change detected by receptor
Stimulus: Produces change in variable
Imbalance
Variable (in homeostasis)
Imbalance
Figure 1.4, step 4

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

18. Feedback Mechanisms
Read the last 2 paragraphs on pg 13
Explain the differences between a negative feedback mechanism and a positive feed back mechanism

19. Negative Feedback
The desire to stop or depress the stimulus

20. Positive feedback
Desire to continue or enhance the stimulus

21. Understanding the analogy
What is the stimulus?
What is the receptor?
What would be the set point?
What represents the effectors?
What is the response?

22. Real life examples of homeostasis
Negative Feedback
Positive Feedback
Blood pressure regulation
Childbirth

23. Practice
When you become dehydrated, and the osmolality of the blood increases (meaning your blood has more salt and less water), osmoreceptors in the hypothalamus cause the posterior pituitary to secrete anti-diuretic hormone (ADH). ADH acts on the kidney to increase the reabsorption of water, and put the water back into your bloodstream. This helps prevent the osmolality of the blood from increasing even further. If you drink lots of water, ADH production decreases, and the kidneys remove water from the blood, again maintaining the osmolality of the blood. Is this a positive or negative feedback loop?

24. Negative Feedback

25. Practice
During sexual intercourse, stimulation leads to an increase in arousal and sexual behavior. This in turn leads to increased stimulation, until climax is reached and orgasm takes place. Is this a positive or negative feedback loop?

26. Positive FeedBack

27. Practice
As a follicle develops in the female ovary, it releases estradiol into the blood. Estradiol stimulates the anterior pituitary to secrete luteinizing hormone (LH), which further stimulates the developing follicle and therefore the production of estradiol. This cycle continues until the follicle ruptures, releasing the egg into the fallopian tube. Is this a positive or negative feedback loop?

28. Positive Feedback

29. Practice
Carbon dioxide is considered a "greenhouse gas" since it absorbs heat that would otherwise dissipate out into space. If there is more carbon dioxide in the atmosphere, global temperatures are likely to increase. It is possible that plants will respond to the increased carbon dioxide and increased temperatures with an increase in photosynthesis. Since carbon dioxide is needed for photosynthesis, this could reduce the amount of carbon dioxide in the atmosphere, leading to cooler temperatures. Is this a positive or negative feedback loop?

30. Negative Feedback

31. Exit Slip Using the index card, answer today’s essential question
Make sure your name is one the card!
What is homeostasis?
Why is it important?
How does it work?