1. Weird Body Quirks Brain freeze
“Ice cream headaches” happen when something cold touches nerves in the roof of the mouth, triggering blood vessels in the front of your head to constrict -- producing pain. Try this quick pain relief trick: Press your tongue to the roof of your mouth to warm it up.

2. HOMEOSTASIS & Control Systems
UNIT 4
Also Known As…
If it ain’t broken, don’t waste my valuable time & energy trying to fix it, fool!

3. When things just work…. Honda Accord – The Cog Commercial

4. Learning goals . . .
To explain the process of maintaining homeostasis through feedback loops and their components.
You will show your understanding by . . .
Presenting an explanation (diagrammatic, written or kinesthetic) of thermoregulation

5. Homeostasis
Regulation of the internal environment through the constant physiological adjustments of the body in response to the external environment changes.
Also known as Dynamic Equilibrium
Requires energy to work
Homios = Similar Stasis = Standing Still
Ideal Body Conditions:
Organs and body systems are constantly adapting
Temperature
37oC (98.6oF)
Blood pH
7.35
Blood sugar level
0.1%

6. Examples of Homeostasis
Class Brainstorm:
Give 3 physical effects observed in your body when you exercise.
What are these factors trying to counteract?
Summary: Sweat(increase body temperature), increase heart rate & breathing rate(increasing oxygen demand), muscle aches(increased cellular respiration but anaerobic occurring d/t insufficient oxygen)
Cell Resp increases
Body Temp increases to 39 degrees Celsius (due to heat from CR rxns)
Sweat is produced to dissipate heat
This loss of water, drops blood pressure
Heart responds, Kidneys conserve water
Electrolytes (salts) are lost in sweat
Body must use hormones to keep a steady supply of glucose to CR pathways
Nervous systems monitors CO2 levels, increasing breathing rate if necessary
Nervous systems also work with the circulatory system to divert blood to essential areas (muscles, brain, heart…away from stomach etc)

7. Homeostasis of Exercise
Body temperature increases
Evaporation of sweat to cool the skin
Oxygen levels being used up
Heart and breathing rate increase to move more blood around (increase blood flow)
Increased cellular metabolism
Pancreas signals the breakdown of biomolecules (glycogen/fat)

8. The Main Internal Dynamic Equilibriums
Water Balance/Blood Pressure
Blood Oxygen/CO2 levels (pH)
Body Temperature
Water/Ion Balance
Blood Glucose (Sugar) Levels
The brain and the adrenal system
(hormones) do most of the
regulating.
All body organ systems work together to maintain homeostasis

9. Homeostasis Dynamic Equilibrium (self-regulation)
Stable within fluctuating limits

10. Common Examples of Homeostatic Balance Being Maintained
Sneezing due to pollen
Asthma attack due to irritants
Birthing hormone oxytocin increasing intensity, duration, and frequency of contractions
Fever due to infection
Kidney’s maintenance of water & ion balance.

11. Forms of Regulation Voluntary  Involuntary 
Requiring though and conscious action
Eg. Rubbing your hands together when cold
Involuntary 
Body adjusts without conscious thought
Eg. Release of insulin after a meal

12. Regulation Mechanisms
1. Osmotic
Pressure differences between 2 solutions on opposite sides of a membrane (semi-permeable)
Eg. Kidney & urine formation, or CO2
2. Hormonal
Chemical messenger
Eg. Growth hormone

13. Regulation Mechanisms
3. Nervous
Works with the endocrine system (into the bloodstream)
involuntary
Eg. Shivering, goose pimples
4. Immune
Defense body against microorganisms and viruses
Eg. fever

14. Negative Feedback Loop

15. Example of a Negative Feedback System

16. Control Systems: 3 functional components
Monitors/Receptors
Senses change
Eg Brain stem receptors detect increased CO2 in the blood, thermoreceptors
Coordinating/Control Centre
Relays message
Eg brain
Regulator/Effector
Restores balance
Eg. Diaphragm increases depth and rate of breathing, blood vessels
Monitor sales and stock of stores and report to factory manager. Based on stocks, factory manager instructs more or less of something to be made. Works increase or decrease production of certain items.

17. Feedback Loops
The fluctuations are kept within an acceptable range by the use of feedback systems
Negative feedback
is most common and restores things back to their original state/acceptable range.
Prevents small changes from becoming large ones
RESISTS change
Positive feedback
amplifies a reaction – reinforces away from equilibrium
Very quick, shuts off once finished

18. Example of a Positive Feedback System

19. Homeostatic Control System
Stimulus
Deviation from set point
Response
Move system towards set point
Sensor
Constantly monitors conditions
Negative feedback (-)
Integrating Centre
Compares conditions to a set point based on a desired value
Effector
Causes changes to compensate for deviation

20. Dynamic Equilibrium There will always be fluctuations in levels
Homeostatic mechanisms ensure that all body systems function within an acceptable range.
Mammalian Diving Reflex
Check out the ICEMAN! es
Homework…Read p (Feedback)
Do Q 2, 4, 9, 10 p348